Stellarium User Guide 0.18.0 1

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Stellarium 0.18.0 User Guide
Georg Zotti, Alexander Wolf (editors)



2014-2017 Georg Zotti.
2011-2017 Alexander Wolf.
2006-2013 Matthew Gates.
2013-2014 Barry Gerdes († 2014).


Permission is granted to copy, distribute and/or modify this document under the terms
of the GNU Free Documentation License, Version 1.3 or any later version published by
the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no
Back-Cover Texts. A copy of the license is included in the appendix G entitled “GNU Free
Documentation License”.
All trademarks, third party brands, product names, trade names, corporate names and company
names mentioned may be trademarks of their respective owners or registered trademarks of other
companies and are used for purposes of explanation and to the readers’ benefit, without implying a
violation of copyright law.
Version 0.18.0-1, March 25, 2018


Basic Use


Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3


Historical notes


Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7


System Requirements
Minimum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Recommended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7





Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OS X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Running Stellarium
Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OS X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .






A First Tour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11


Time Travel



Moving Around the Sky




The Main Tool Bar



Taking Screenshots



The User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19


Setting the Date and Time



Setting Your Location



The Configuration Window
The Main Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Information Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Navigation Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Tools Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Scripts Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Plugins Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



The View Settings Window
The Sky Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Deep-Sky Objects (DSO) Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Markings Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Landscape Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Starlore Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Surveys Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



The Object Search Window



The Astronomical Calculations Window
The Positions Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Ephemeris Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Phenomena Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The “Altitude vs. Time” Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Graphs Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The “What’s Up Tonight” (WUT) Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The “Planetary Calculator” (PC) Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Help Window
Editing Keyboard Shortcuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40


Advanced Use


Files and Directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45


Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mac OS X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Directory Structure



The Logfile



The Main Configuration File



Getting Extra Data
More Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
More Deep-Sky Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alternative Planet Ephemerides: DE430, DE431 . . . . . . . . . . . . . . . . . . . .
GPS Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Command Line Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51




Special Options
Spout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53


Landscapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55


Stellarium Landscapes
Location information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Polygonal landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Spherical landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High resolution (“Old Style”) landscape . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fisheye landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gazetteer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Packing and Publishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Creating Panorama Photographs for Stellarium
Panorama Photography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hugin Panorama Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Regular creation of panoramas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Panorama Postprocessing
The GIMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ImageMagick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Final Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Artificial Panoramas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nightscape Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Other recommended software
IrfanView . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FSPViewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Clink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cygwin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GNUWin32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Deep-Sky Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79


Stellarium DSO Catalog
Modifying catalog.dat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Modifying names.dat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Modifying textures.json . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Modifying outlines.dat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .




Adding Extra Nebulae Images
Preparing a photo for inclusion to the textures.json file . . . . . . . . . . . . .
Plate Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Processing into a textures.json insert . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Adding Sky Cultures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89


Basic Information



Skyculture Description Files



Constellation Names



Star Names



Planet Names



Deep-Sky Objects Names



Stick Figures



Constellation Boundaries



Constellation Artwork



Seasonal Rules






Asterisms and help rays



Publish Your Work



Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95





Hipslist file and default surveys



Solar system HiPS survey


Extending Stellarium


Plugins: An Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99


Enabling plugins



Data for plugins



Interface Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101


Angle Measure Plugin



Compass Marks Plugin



Equation of Time Plugin


12.3.1 Section EquationOfTime in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . 103

Field of View Plugin


12.4.1 Section FOV in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Pointer Coordinates Plugin


12.5.1 Section PointerCoordinates in config.ini file . . . . . . . . . . . . . . . . . . . . . 105

Text User Interface Plugin
12.6.1 Using the Text User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
12.6.2 TUI Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106


12.6.3 Section tui in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Remote Control Plugin
Using the plugin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Remote Control Web Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Remote Control Commandline API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Developer information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Remote Sync Plugin



Solar System Editor Plugin



Object Catalog Plugins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117


Bright Novae Plugin


13.1.1 Section Novae in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
13.1.2 Format of bright novae catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
13.1.3 Light curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Historical Supernovae Plugin
13.2.1 List of supernovae in default catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
13.2.2 Light curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

13.2.3 Section Supernovae in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
13.2.4 Format of historical supernovae catalog . . . . . . . . . . . . . . . . . . . . . . . . . 122
Exoplanets Plugin
13.3.1 Potential habitable exoplanets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
13.3.2 Proper names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

13.3.3 Section Exoplanets in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
13.3.4 Format of exoplanets catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Pulsars Plugin


13.4.1 Section Pulsars in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
13.4.2 Format of pulsars catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

Quasars Plugin


13.5.1 Section Quasars in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
13.5.2 Format of quasars catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Meteor Showers Plugin
13.6.1 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

13.6.2 Section MeteorShowers in config.ini file . . . . . . . . . . . . . . . . . . . . . . . . 134
13.6.3 Format of Meteor Showers catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
13.6.4 Further Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Navigational Stars Plugin


13.7.1 Section NavigationalStars in config.ini file . . . . . . . . . . . . . . . . . . . . . . 137


Satellites Plugin
Satellite Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Iridium Flares prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Satellite Catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sources for TLE data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



ArchaeoLines Plugin
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Characteristic Declinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Azimuth Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Arbitrary Declination Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Scenery3d – 3D Landscapes . . . . . . . . . . . . . . . . . . . . . . . . . . . 145







Hardware Requirements & Performance
14.3.1 Performance notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Model Configuration
Exporting OBJ from Sketchup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Notes on OBJ file format limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuring OBJ for Scenery3d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Concatenating OBJ files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Beyond 3D: Temporally evolving Models . . . . . . . . . . . . . . . . . . . . . . . . .
Working with non-georeferenced OBJ files . . . . . . . . . . . . . . . . . . . . . . .
Rotating OBJs with recognized survey points . . . . . . . . . . . . . . . . . . . . .



Predefined views






Stellarium at the Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159


Oculars Plugin
Using the Ocular plugin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Scaling the eyepiece view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



TelescopeControl Plugin
Abilities and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using this plug-in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Main window (’Telescopes’) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Telescope configuration window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Supported devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .












Other telescope servers and Stellarium



Observability Plugin



Scripting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183





Script Console






Minimal Scripts


Example: Retrograde motion of Mars
16.5.1 Script header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
16.5.2 A body of script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

More Examples


Practical Astronomy


Astronomical Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191


The Celestial Sphere



Coordinate Systems
Altitude/Azimuth Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Right Ascension/Declination Coordinates . . . . . . . . . . . . . . . . . . . . . . . .
Ecliptical Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Galactic Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .






Sidereal Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Julian Day Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Delta T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


17.5.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
17.5.2 Handy Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

The Magnitude Scale








17.9.1 Geocentric and Topocentric Observations . . . . . . . . . . . . . . . . . . . . . . . 205
17.9.2 Stellar Parallax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
17.10 Proper Motion



Astronomical Phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207


The Sun


18.2.1 Multiple Star Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
18.2.2 Constellations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

18.2.3 Star Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
18.2.4 Spectral Type & Luminosity Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
18.2.5 Variable Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
Our Moon
18.3.1 Phases of the Moon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
The Major Planets
18.4.1 Terrestrial Planets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
18.4.2 Jovian Planets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
The Minor Bodies
18.5.1 Asteroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
18.5.2 Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215




Zodiacal Light and Gegenschein



The Milky Way


18.9.1 The Messier Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
18.10 Galaxies


18.11 Eclipses
18.11.1 Solar Eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
18.11.2 Lunar Eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
18.12 Observing Hints


18.13 Atmospheric effects
18.13.1 Atmospheric Extinction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.13.2 Atmospheric Refraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.13.3 Light Pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



A Little Sky Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223


Dubhe and Merak, The Pointers



M31, Messier 31, The Andromeda Galaxy



The Garnet Star, µ Cephei



4 and 5 Lyrae, ε Lyrae



M13, Hercules Cluster



M45, The Pleiades, The Seven Sisters



Algol, The Demon Star, β Persei



Sirius, α Canis Majoris



M44, The Beehive, Praesepe


19.10 27 Cephei, δ Cephei


19.11 M42, The Great Orion Nebula


19.12 La Superba, Y Canum Venaticorum, HIP 62223


19.13 52 and 53 Bootis,






19.14 PZ Cas, HIP 117078


19.15 VV Cephei, HIP 108317


19.16 AH Scorpii, HIP 84071


19.17 Albireo, β Cygni
19.18 31 and 32 Cygni,






19.19 The Coathanger, Brocchi’s Cluster, Cr 399


19.20 Kemble’s Cascade


19.21 The Double Cluster, χ and h Persei, NGC 884 and NGC 869


19.22 Large Magellanic Cloud, PGC 17223


19.23 Tarantula Nebula, C 103, NGC 2070


19.24 Small Magellanic Cloud, NGC 292, PGC 3085


19.25 ω Centauri cluster, C 80, NGC 5139


19.26 47 Tucanae, C 106, NGC 104


19.27 The Coalsack Nebula, C 99


19.28 Mira, o Ceti, 68 Cet


19.29 α Persei Cluster, Cr 39, Mel 20


19.30 M7, The Ptolemy Cluster


19.31 M24, The Sagittarius Star Cloud


19.32 IC 4665, The Summer Beehive Cluster


19.33 The E Nebula, Barnard 142 and 143



Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

Find M31 in Binoculars
20.1.1 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
20.1.2 For Real . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

Handy Angles



Find a Lunar Eclipse



Find a Solar Eclipse



Find a retrograde motion of Mars






Transit of Venus



Transit of Mercury



Triple shadows on Jupiter


20.10 Jupiter without satellites


20.11 Mutual occultations of planets


20.12 The proper motion of stars




Default Hotkeys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239


Mouse actions with combination of the keyboard keys



Display Options






Movement and Selection



Date and Time









Angle Measure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ArchaeoLines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Compass Marks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Equation of Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exoplanets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Field of View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Meteor Showers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oculars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulsars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Quasars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Satellites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Scenery3d: 3D landscapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Solar System Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Telescope Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



The Bortle Scale of Light Pollution . . . . . . . . . . . . . . . . . . . . . . 247


Excellent dark sky site



Typical truly dark site



Rural sky



Rural/suburban transition



Suburban sky



Bright suburban sky



Suburban/urban transition



City sky



Inner-city sky



Star Catalogues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251


Stellarium’s Sky Model
Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251


Star Catalogue File Format
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
File Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Record Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Variable Stars
Variable Star Catalog File Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
GCVS Variability Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256



Double Stars
Double Star Catalog File Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269


Cross-Identification Data
Cross-Identification Catalog File Format . . . . . . . . . . . . . . . . . . . . . . . . . 269


Configuration Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271



astro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

astrocalc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

color . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

custom_selected_info . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

custom_time_correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

devel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

dso_catalog_filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

dso_type_filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
gui . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

init_location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

main . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

plugins_load_at_startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

proxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

spheric_mirror . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
tui . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

viewing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DialogPositions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DialogSizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Solar System Configuration Files
File ssystem_major.ini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
File ssystem_minor.ini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295



hips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290


Planetary nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299


Format of nomenclature data file



How names are approved by the IAU



IAU rules and conventions



Naming conventions



Descriptor terms (feature types)



Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305


Date Range



Stellar Proper Motion



Planetary Positions



Minor Bodies



Precession and Nutation



Planet Axes






The Calendar



GNU Free Documentation License . . . . . . . . . . . . . . . . . . . . . 309






































Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317





How you can help



Technical Articles



Included Source Code






Image Credits
Full credits for “earthmap” texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
License for the JPL planets images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335


Basic Use


Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3


Historical notes


Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7


System Requirements
Running Stellarium


A First Tour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11


Time Travel
Moving Around the Sky
The Main Tool Bar
Taking Screenshots


The User Interface . . . . . . . . . . . . . . . . . . . . . . . . . 19


Setting the Date and Time
Setting Your Location
The Configuration Window
The View Settings Window
The Object Search Window
The Astronomical Calculations Window
Help Window

1. Introduction

Stellarium is a software project that allows people to use their home computer as a virtual planetarium. It calculates the positions of the Sun and Moon, planets and stars, and draws how the
sky would look to an observer depending on their location and the time. It can also draw the
constellations and simulate astronomical phenomena such as meteor showers or comets, and solar
or lunar eclipses.
Stellarium may be used as an educational tool for teaching about the night sky, as an observational aid for amateur astronomers wishing to plan a night’s observing or even drive their
telescopes to observing targets, or simply as a curiosity (it’s fun!). Because of the high quality
of the graphics that Stellarium produces, it is used in some real planetarium projector products
and museum projection setups. Some amateur astronomy groups use it to create sky maps for
describing regions of the sky in articles for newsletters and magazines, and the exchangeable sky
cultures feature invites its use in the field of Cultural Astronomy research and outreach.
Stellarium is still under development, and by the time you read this guide, a newer version may
have been released with even more features than those documented here. Check for updates to
Stellarium at the Stellarium website1 .
If you have questions and/or comments about this guide, or about Stellarium itself, visit the
Stellarium site at Github2 or our Google Groups forum3 .


Historical notes
Fabien Chéreau started the project during the summer 2000, and throughout the years found
continuous support by a small team of enthusiastic developers.
Here is a list of past and present major contributors sorted roughly by date of arrival on the


Chapter 1. Introduction


Fabien Chéreau original creator, maintainer, general development
Matthew Gates maintainer, original user guide, user support, general development
Johannes Gajdosik astronomical computations, large star catalogs support
Johan Meuris GUI design, website creation, drawings of our 88 Western constellations
Nigel Kerr Mac OSX port
Rob Spearman funding for planetarium support
Barry Gerdes user support, tester, Windows support. Barry passed away in October 2014 at age
80. He was a major contributor on the forums, wiki pages and mailing list where his good
will and enthusiasm is strongly missed. RIP Barry.
Timothy Reaves ocular plugin
Bogdan Marinov GUI, telescope control, other plugins
Diego Marcos SVMT plugin
Guillaume Chéreau display, optimization, Qt upgrades, HiPS surveys
Alexander Wolf maintainer, DSO catalogs, user guide, general development
Georg Zotti astronomical computations, Scenery 3D and ArchaeoLines plugins, general development, user guide, user support
Marcos Cardinot MeteorShowers plugin
Florian Schaukowitsch Scenery 3D plugin, Remote Control plugin, RemoteSync plugin, OBJ
rendering, Qt/OpenGL internals
Teresa Huertas Roldán Planetary nomenclature
Unfortunately time is evolving, and most members of the original development team are no
longer able to devote most of their spare time to the project (some are still available for limited
work which requires specific knowledge about the project).
As of 2017, the project’s maintainer is Alexander Wolf, doing most maintenance and regular
releases. Major new features are contributed mostly by Georg Zotti and his team focussing on
extensions of Stellarium’s applicability in the fields of historical and cultural astronomy research
(which means Stellarium is getting more accurate) and outreach (making it usable for museum
installations), but also on graphic items like comet tails or the Zodiacal Light.
A detailed track of development can be found in the ChangeLog file in the installation folder. A
few important milestones for the project:
2000 first lines of code for the project
2001-06 first public mention (and users feedbacks!) of the software on the French newsgroup
fr.sci.astronomie.amateur 4
2003-01 Stellarium reviewed by Astronomy magazine
2003-07 funding for developing planetarium features (fisheye projection and other features)
2005-12 use accurate (and fast) planetary model
2006-05 Stellarium “Project Of the Month” on SourceForge
2006-08 large stars catalogs
2007-01 funding by ESO for development of professional astronomy extensions (VirGO)
2007-04 developers’ meeting near Munich, Germany
2007-05 switch to the Qt library as main GUI and general purpose library
2009-09 plugin system, enabling a lot of new development
2010-07 Stellarium ported on Maemo mobile device
2010-11 artificial satellites plugin
2014-06 high quality satellites and Saturn rings shadows, normal mapping for moon craters
2014-07 v0.13.0: adapt to OpenGL evolutions in the Qt framework, now requires more modern


1.1 Historical notes


graphic hardware than earlier versions
2015-04 v0.13.3: Scenery 3D plugin
2015-10 v0.14.0: Accurate precession
2016-07 v0.15.0: Remote Control plugin
2016-12 v0.15.1: DE430&DE431, AstroCalc, DSS layer, and Stellarium acting as SpoutSender
2017-06 v0.16.0: Remote Sync plugin, polygonal OBJ models for minor bodies, RTS2 telescope
2017-09 v0.16.1: Standard and extended DSO catalog, new subcatalogues for DSO
2017-12 v0.17.0: Nomenclature labels for planets and moons, INDI telescope support
2018-03 v0.18.0: Multiple image surveys
Stellarium has been kindly supported by ESA in their Summer of Code in Space initiatives,
which so far has resulted in better planetary rendering (2012), the Meteor Showers plugin (2013),
the web-based remote control and an alternative solution for planetary positions based on the
DE430/DE431 ephemeris (2015), the RemoteSync plugin and OBJ models (2016), and the planet
nomenclature labels (2017).
This guide is based on the user guide written by Matthew Gates for version 0.10 around 2008.
The guide was then ported to the Stellarium wiki and continuously updated by Barry Gerdes
and Alexander Wolf up to version 0.12. Unfortunately, some new features were not properly
documented in the wiki, and generally, without Barry the wiki started to fall out of sync with the
actual program. In late 2015 we (Alexander and Georg) started porting the texts back to LATEX and
updated and added information where necessary, or wrote new chapters for the features which were
introduced in the last years. We feel that a single book is the better format for offline reading. The
PDF version of this guide has a clickable table of contents and clickable hyperlinks.
These new editions of the Guide (since V0.15) will not contain notes about using earlier
versions than 0.13 or using very outdated hardware. New features are marked with a version
number like 0.15.2 in the margin. Some references to previous versions may still be made for
completeness, but if you are using earlier versions of Stellarium for particular reasons, please use
the older guides.

2. Getting Started


System Requirements
Stellarium has been seen to run on most systems where Qt5 is available, from tiny ARM computers
like the Raspberry Pi 2/31 or Odroid C1 to big museum installations with multiple projectors and
planetaria with fish-eye projectors. The most important hardware requirement is a contemporary
graphics subsystem.


• Linux/Unix; Windows 7 and later (It may run on Vista, but unsupported. A special version
for XP is still available); Mac OS X 10.10.0 and later
• 3D graphics capabilities which support OpenGL 3.0 and GLSL 1.3 (2008 GeForce 8xxx and
later, ATI/AMD Radeon HD-2xxx and later; Intel HD graphics (Core-i 2xxx and later)) or
OpenGL ES 2.0 and GLSL ES 1.0 (e.g., ARM SBCs like Raspberry Pi 2/3). On Windows,
some older cards may be supported via ANGLE when they support DirectX10.
• 512 MB RAM
• 250 MB free on disk



1 As

Linux/Unix; Windows 7 and later; Mac OS X 10.10.0 and later
3D graphics card which supports OpenGL 3.3 and above and GLSL1.3 and later
1 GB RAM or more
1.5 GB free on disk (About 3GB extra required for the optional DE430/DE431 files).
A dark room for realistic rendering — details like the Milky Way, Zodiacal Light or star
twinkling can’t be seen in a bright room.

of autumn 2017, you need to enable the experimental OpenGL driver and compile the drm and
Mesa 17 libraries from sources. See 2.3.3

Chapter 2. Getting Started



Download the correct package for your operating system directly from the main page, An archive of all available versions is available at https://sourceforge.




1. Double click on the installer file you downloaded:
• stellarium-0.18.0-win64.exe for 64-bit Windows 7 and later.
• stellarium-0.18.0-win32.exe for 32-bit Windows 7 and later.
• stellarium-0.18.0-classic-win32.exe for Windows XP and later.
2. Follow the on-screen instructions.


1. Locate the Stellarium-0.18.0.dmg file in Finder and double click on it or open it using
the Disk Utility application. Now, a new disk appears on your desktop and Stellarium is in it.
2. Open the new disk and please take a moment to read the ReadMe file. Then drag Stellarium
to the Applications folder.
3. Note: You should copy Stellarium to the Applications folder before running it — some users
have reported problems running it directly from the disk image (.dmg).


Check if your distribution has a package for Stellarium already — if so you’re probably best off
using it. If not, you can download and build the source.
For Ubuntu we provide a package repository with the latest stable releases. Open a terminal
and type:
sudo add - apt - repository ppa : stellarium / stellarium - releases
sudo apt - get update
sudo apt - get install stellarium
Raspberry Pi 2/3
These tiny ARM-based computers are very popular for small and energy-efficient applications like
controlling push-to Dobsonians. A new open-source OpenGL driver stack has been made available
recently, but as of October 2017 the default Raspbian operating system comes with an outdated
version. Stellarium requires Mesa 17 or later. To set up a Raspberry Pi 2 or 3 with Raspbian
Stretch for use with Stellarium, activate the OpenGL driver in raspi-config and follow instructions
from the VC4 wiki.2 The libdrm upgrade is required and does not harm, but you can also install
Mesa 17 in addition to the stock Mesa 13 following another set of instructions.3
For Ubuntu 16.04 LTS, follow instructions4 .
Note that as of October 2017 (Mesa 17.4) the 3D planets do not work.

You only need
to follow the instructions on first boot, libdrm and Mesa.
Note that you may
need to add a symbolic link to the VC4 library.
With all paths from these instructions,
ln -s ~/prefix/dri/ ~/prefix/ should do the trick.

2.4 Running Stellarium



Running Stellarium


The Stellarium installer creates a whole list of items in the Start Menu under the Programs/Stellarium section. The list evolves over time, not all entries listed here may be installed on your
system. Select one of these to run Stellarium:
Stellarium OpenGL version. This is the most efficient for modern PCs and should be used
when you have installed appropriate OpenGL drivers. Note that some graphics cards are
“blacklisted” by Qt to immediately run via ANGLE (Direct3D), you cannot force OpenGL in
this case. This should not bother you.
Stellarium (ANGLE mode) Uses Direct3D translation of the OpenGL rendering via ANGLE
library. Forces Direct3D version 9.
Stellarium (MESA mode) Uses software rendering via MESA library. This should work on any
PC without dedicated graphics card.
On startup, a diagnostic check is performed to test whether the graphics hardware is capable of
running. If all is fine, you will see nothing of it. Else you may see an error panel informing you
that your computer is not capable of running Stellarium (“No OpenGL 2 found”), or a warning
that there is only OpenGL 2.1 support. The latter means you will be able to see some graphics,
but depending on the type of issue you will have some bad graphics. For example, on an Intel
GMA4500 there is only a minor issue in Night Mode, while on other systems we had reports of
missing planets or even crashes as soon as a planet comes into view. If you see this, try running in
Direct3D 9 or MESA mode, or upgrade your system. The warning, once ignored, will not show
When you have found a mode that works on your system, you can delete the other links.


Double click on the Stellarium application. Add it to your Dock for quick access.


If your distribution had a package you’ll probably already have an item in the GNOME or KDE
application menus. If not, just open a terminal and type stellarium.


Stellarium writes startup and other diagnostic messages into a logfile. Please see section 5.3 where
this file is located on your system. This file is essential in case when you feel you need to report a
problem with your system which has not been found before.
If you don’t succeed in running Stellarium, please see the online forum5 . It includes FAQ
(Frequently Asked Questions, also Frequently Answered Questions) and a general question section
which may include further hints. Please make sure you have read and understood the FAQ before
asking the same questions again.


3. A First Tour

Figure 3.1: Stellarium main view. (Combination of day and night views.)
When Stellarium first starts, we see a green meadow under a sky. Depending on the time of day, it
is either a day or night scene. If you are connected to the Internet, an automatic lookup will attempt
to detect your approximate position.1
1 See

section 4.2 if you want to switch this off.

Chapter 3. A First Tour


At the bottom left of the screen, you can see the status bar. This shows the current observer
location, field of view (FOV), graphics performance in frames per second (FPS) and the current
simulation date and time. If you move the mouse over the status bar, it will move up to reveal a tool
bar which gives quick control over the program.
The rest of the view is devoted to rendering a realistic scene including a panoramic landscape
and the sky. If the simulation time and observer location are such that it is night time, you will see
stars, planets and the moon in the sky, all in the correct positions.
You can drag with the mouse on the sky to look around or use the cursor keys. You can zoom
with the mouse wheel or the Page or Page keys.
Much of Stellarium can be controlled very intuitively with the mouse. Many settings can
additionally be switched with shortcut keys (hotkeys). Advanced users will learn to use these
shortcut keys. Sometimes a key combination will be used. For example, you can quit Stellarium by
+ Q on Mac OS X. For simplicity, we will
pressing Ctrl + Q on Windows and Linux, and
show only the Windows/Linux version. We will present the default hotkeys in this guide. However,
almost all hotkeys can be reconfigured to match your taste. Note that some listed shortkeys are only
available as key combinations on international keyboard layouts, e.g., keys which require pressing
AltGr on a German keyboard. These must be reconfigured, please see 4.7.1 for details.
The way Stellarium is shown on the screen is primarily governed by the menus. These are
accessed by dragging the mouse to the left or bottom edge of the screen, where the menus will slide
out. In case you want to see the menu bars permanently, you can press the small buttons right in the
lower left corner to keep them visible.


Time Travel
When Stellarium starts up, it sets its clock to the same time and date as the system clock. However,
Stellarium’s clock is not fixed to the same time and date as the system clock, or indeed to the
same speed. We may tell Stellarium to change how fast time should pass, and even make time
go backwards! So the first thing we shall do is to travel into the future! Let’s take a look at the
time control buttons on the right hand ride of the tool-bar. If you hover the mouse cursor over the
buttons, a short description of the button’s purpose and keyboard shortcut will appear.


Shortcut key



Decrease the rate at which time passes


Make time pass as normal


Increase the rate at which time passes


Return to the current time & date
Table 3.1: Time Travel

OK, so lets go see the future! Click the mouse once on the increase time speed button
Not a whole lot seems to happen. However, take a look at the clock in the status bar. You should
see the time going by faster than a normal clock! Click the button a second time. Now the time is
going by faster than before. If it’s night time, you might also notice that the stars have started to

3.2 Moving Around the Sky


move slightly across the sky. If it’s daytime you might be able to see the sun moving (but it’s less
apparent than the movement of the stars). Increase the rate at which time passes again by clicking
on the button a third time. Now time is really flying!
Let time move on at this fast speed for a little while. Notice how the stars move across the sky.
If you wait a little while, you’ll see the Sun rising and setting. It’s a bit like a time-lapse movie.
Stellarium not only allows for moving forward through time – you can go backwards too! Click
on the real time speed button

. The stars and/or the Sun should stop scooting across the sky.

Now press the decrease time speed button
once. Look at the clock. Time has stopped. Click
the decrease time speed button four or five more times. Now we’re falling back through time at
quite a rate (about one day every ten seconds!).
Time Dragging, Time Scrolling
Another way to quickly change time is time dragging. Press Ctrl and slide the mouse along the
direction of daily motion to go forward, or to the other direction to go backward.
Similarly, pressing Ctrl and scrolling the mouse wheel will advance time by minutes, pressing
Ctrl +
and scrolling the mouse wheel will advance time by hours, Ctrl + Alt by days, and finally
+ Alt by calendar years.
Ctrl +
Enough time travel for now. Wait until it’s night time, and then click the real time speed button
. With a little luck you will now be looking at the night sky.


Moving Around the Sky


Cursor keys
Page / Page , Ctrl +
/ Ctrl +
Left mouse button
Right mouse button
Centre mouse button (wheel press)
Mouse wheel

Pan the view left, right, up and down
Zoom in and out
Select an object in the sky
Clear selected object
Centre selected object and start tracking
Zoom in and out
Centre view on selected object
Auto-zoom in to selected object
Auto-zoom out to original field of view

Forward-slash ( / )
Backslash ( \ )

Table 3.2: Moving Around the Sky
As well as travelling through time, Stellarium lets to look around the sky freely, and zoom in
and out. There are several ways to accomplish this listed in table 3.2.
Let’s try it. Use the cursors to move around left, right, up and down. Zoom in a little using
the Page key, and back out again using the Page . Press the \ key and see how Stellarium
returns to the original field of view (how “zoomed in” the view is), and direction of view.
It’s also possible to move around using the mouse. If you left-click and drag somewhere on the
sky, you can pull the view around.
Another method of moving is to select some object in the sky (left-click on the object), and
press the Space key to centre the view on that object. Similarly, selecting an object and pressing
the forward-slash key / will centre on the object and zoom right in on it.


Chapter 3. A First Tour


The forward-slash / and backslash \ keys auto-zoom in an out to different zoom levels
depending on what is selected. If the object selected is a planet or moon in a sub-system with a lot of
moons (e.g. Jupiter), the initial zoom in will go to an intermediate level where the whole sub-system
should be visible. A second zoom will go to the full zoom level on the selected object. Similarly, if
you are fully zoomed in on a moon of Jupiter, the first auto-zoom out will go to the sub-system
zoom level. Subsequent auto-zoom out will fully zoom out and return the initial direction of view.
For objects that are not part of a sub-system, the initial auto-zoom in will zoom right in on the
selected object (the exact field of view depending on the size/type of the selected object), and the
initial auto-zoom out will return to the initial FOV and direction of view.


The Main Tool Bar

Figure 3.2: Night scene with constellation artwork and moon.
Stellarium can do a whole lot more than just draw the stars. Figure 3.2 shows some of
Stellarium’s visual effects including constellation line and boundary drawing, constellation art,
planet hints, and atmospheric halo around the bright Moon. The controls in the main tool bar
provide a mechanism for turning on and off the visual effects.
When the mouse if moved to the bottom left of the screen, a second tool bar becomes visible.
All the buttons in this side tool bar open and close dialog boxes which contain controls for further
configuration of the program. The dialogs will be described in the next chapter.
Table 3.3 describes the operations of buttons on the main tool bar and the side tool bar, and
gives their default keyboard shortcuts.

3.3 The Main Tool Bar






Draw constellations as “stick figures”

Constellation Names


Draw name of the constellations

Constellation Art


Superimpose artistic representations
of the constellations

Constellation Boundaries


Draw boundaries of the constellations 1

Equatorial Grid


Draw grid lines for the equatorial
coordinate system (RA/Dec)

Azimuth Grid


Draw grid lines for the horizontal
coordinate system (Alt/Azi)

Galactic Grid

Draw grid lines for the galactic coordinate system (Long/Lat) 1

Equatorial J2000 Grid

Draw grid lines for the equatorial
coordinate system at standard epoch
J2000.0 (RA/Dec) 1

Ecliptic Grid

Draw grid lines for the ecliptic coordinate system of date (Long/Lat)

Toggle Ground


Toggle drawing of the ground. Turn
this off to see objects that are below
the horizon.

Toggle Cardinal Points


Toggle marking of the North, South,
East and West points on the horizon.

Toggle Atmosphere


Toggle atmospheric effects. Most
notably makes the stars visible in the

Deep-Sky Objects


Toggle marking the positions of
Deep-Sky Objects.

Planet Hints


Toggle indicators to show the position of planets.

Nebula images


Toggle “nebula images”.

Digitized Sky Survey

Ctrl + Alt + D


Toggle “Digitized Sky Survey”.1

Chapter 3. A First Tour

Ctrl + M

Coordinate System

Toggle between horizontal (Alt/Azi)
& equatorial (RA/Dec) coordinate
Center the view on the selected object


Ctrl + N

Night Mode


Full Screen Mode

Toggle full screen mode.

Alt + B


Toggle “night mode”, which applies
a red-only filter to the view to be
easier on the dark-adapted eye.

Toggle bookmarks window.

Flip view (horizontal)

Ctrl + Shift + H

Flip view (vertical)

Ctrl + Shift + V


Flip the image in the horizontal
plane. 1
Flip the image in the vertical plane.

Ctrl + Q

Quit Stellarium

Close Stellarium.

Help Window


Show the help window, with key
bindings and other useful information

Configuration Window


Show the configuration window

Search Window


or Ctrl

+ F

Show the object search window

View Window


Show the view window

Time Window


Show the time window

Location Window


Show the observer location window

AstroCalc Window


Show the astronomical calculations

Table 3.3: Stellarium’s standard menu buttons. Those marked
must be enabled first, see section 4.3.4.


3.4 Taking Screenshots



Taking Screenshots
You can save what is on the screen to a file by pressing Ctrl + S . Screenshots are taken in
PNG format, and have filenames like stellarium-000.png, stellarium-001.png (the number
increments to prevent overwriting existing files).
Stellarium creates screenshots in a directory depending on your operating system, see section
5.1 Files and Directories.

4. The User Interface

This chapter describes the dialog windows which can be accessed from the left menu bar.
Most of Stellarium’s settings can be changed using the view window (press
the configuration window (

or F4 ) and

or F2 ). Most settings have short labels. To learn more about

some settings, more information is available as tooltips, small text boxes which appear when you
hover the mouse cursor over a button.1
You can drag the windows around, and the position will be used again when you restart
Stellarium. If this would mean the window is off-screen (because you start in windowed mode, or
with a different screen), the window will be moved so that at least a part is visible.
Some options are really rarely changed and therefore may only be configured by editing the
configuration file. See 5.4 The Main Configuration File for more details.


Setting the Date and Time

Figure 4.1: Date and Time dialog
In addition to the time rate control buttons on the main toolbar, you can use the date and time
1 Unfortunately,

on Windows 7 and later, with some NVidia and AMD GPUs in OpenGL mode, these
tooltips often do not work.


Chapter 4. The User Interface

window (open with the

button or F5 ) to set the simulation time. The values for year, month,

day, hour, minutes and seconds may be modified by typing new values, by clicking the up and down
arrows above and below the values, and by using the mouse wheel.
The other tab in this window allows you to see or set Julian Day and/or Modified Julian Day
numbers (see 17.4.2).


Setting Your Location

Figure 4.2: Location window


The positions of the stars in the sky is dependent on your location on Earth (or other planet) as well
as the time and date. For Stellarium to show accurately what is (or will be/was) in the sky, you
must tell it where you are. You only need to do this once – Stellarium can save your location so
you won’t need to set it again until you move.
After installation, Stellarium uses an online service which tries to find your approximate
location based on the IP address you are using. This seems very practical, but if you feel this causes
privacy issues, you may want to switch this feature off. You should also consider switching it off
on a computer which does not move, to save network bandwidth.
To set your location more accurately, or if the lookup service fails, press F6 to open the
location window (Fig. 4.2). There are a few ways you can set your location:
1. Just click on the map.
2. Search for a city where you live using the search edit box at the top right of the window, and
select the right city from the list.
3. Click on the map to filter the list of cities in the vicinity of your click, then choose from the

4.3 The Configuration Window


4. Enter a new location using the longitude, latitude and other data.
5. Click on Get Location from GPS if you have a GPS receiver. See section 5.5.4 for configuration
details. Sometimes you have to try several times to get a valid 3D fix including altitude.
If you want to use the current location permanently, click on the “use as default” checkbox, disable
“Get location from Network”, and close the location window.


The Configuration Window
The configuration window contains general program settings, and many other settings which do not
concern specific display options. Press the tool button


or F2 to open.

The Main Tab
The Main tab in the configuration window provides controls for changing separately the program
and sky culture languages.
The next setting group allows to enable using DE430/DE431 ephemeris files. These files have
to be installed separately. Most users do not require this. See section 5.5.3 if you are interested.
The tab also provides the buttons for saving the current view direction as default for the next
startup, and for saving the program configuration. Most display settings have to be explicitly stored
to make a setting change permanent.


The Information Tab
The Information tab allows you to set the type and amount of information displayed about a selected
• Ticking or unticking the relevant boxes will control this.
• The information displays in various colours depending on the type and level of the stored
• Additional settings for the information display


The Navigation Tab
The Navigation tab (Fig. 4.5) allows for enabling/disabling of keyboard shortcuts for panning and
zooming the main view, and also how to specify what simulation time should be used when the
program starts:
System date and time Stellarium will start with the simulation time equal to the operating system
System date at Stellarium will start with the same date as the operating system clock, but the
time will be fixed at the specified value. This is a useful setting for those people who use
Stellarium during the day to plan observing sessions for the upcoming evening.
Other some fixed time can be chosen which will be used every time Stellarium starts.
The lowest field allows selection of the correction model for the time correction ∆T (see section 17.4.3). Default is “Espenak and Meeus (2006)”. Please use other values only if you know
what you are doing.


The Tools Tab
The Tools tab (Fig. 4.6) contains miscellaneous utility features, and also allows to hide or show
additional buttons in the lower button bar. If your screen is too narrow to show all buttons, you may
have to choose your optimal setup.



Chapter 4. The User Interface

Figure 4.3: Configuration Window: Main Tab

Figure 4.4: Configuration Window: Information Tab

4.3 The Configuration Window

Figure 4.5: Configuration Window: Navigation Tab

Figure 4.6: Configuration Window: Tools Tab



Chapter 4. The User Interface

Figure 4.7: Configuration Window: Scripts Tab

Figure 4.8: Configuration Window: Plugins Tab

4.3 The Configuration Window


Spheric mirror distortion This option pre-warps the main view such that it may be projected
onto a spherical mirror using a projector. The resulting image will be reflected up from the
spherical mirror in such a way that it may shine onto a small planetarium dome (or even just
the ceiling of your dining room), making a cheap planetarium projection system.
Select single constellation When active, clicking on a star that is member in the constellation
lines will make the constellation stand out. You can select several constellations, but clicking
onto a star which is not member of a constellation line will display all constellations.
Show nebula background button You can disable display of DSO photographs with this button.
Show bookmarks button You can enable display of Bookmarks dialog with this button.
Show ICRS grid button You can toggle display of equatorial J2000 coordinate grid with this
Show ecliptic grid button You can toggle display of ecliptic coordinate grid with this button.
Auto-enabling for the atmosphere When changing planet during location change, atmosphere
will be switched as required.
Include nutation Compute the slight wobble of earth’s axis. This feature is active only about 500
years around J2000.0.
Azimuth from South Some users may be used to counting azimuth from south.
Use buttons background Applies a gray background under the buttons on the bottom bar.
Auto zoom out returns to initial direction of view When enabled, this option changes the behaviour of the zoom out key \ so that it resets the initial direction of view in addition to
the field of view.
Disc viewport This option masks the main view producing the effect of a telescope eyepiece. It is
also useful when projecting Stellarium’s output with a fish-eye lens planetarium projector.
Gravity labels This option makes labels of objects in the main view align with the nearest horizon.
This means that labels projected onto a dome are always aligned properly.
Show flip buttons When enabled, two buttons will be added to the main tool bar which allow
the main view to be mirrored in the vertical and horizontal directions. This is useful when
observing through telecopes which may cause the image to be mirrored.
Show DSS button You can toggle display of Digitized Sky Survey with this button.
Show galactic grid button You can toggle display of galactic coordinate grid with this button.
Show constellation boundaries button You can toggle display of constellation boundaries with
this button.
Use decimal degrees You can toggle usage of decimal degree format for coordinates.
Topocentric coordinates If you require planetocentric coordinates, you may switch this off. Usually it should be enabled. (See 17.9.1)
Auto select landscapes When changing the planet in the location panel, a fitting landscape
panorama will be shown when available.
Indication for mount mode You can activate the short display of a message when switching type
of used mount.
In addition, you can set the directory where screenshots will be stored, and you can download more
star catalogs on this tab.

The Scripts Tab
The Scripts tab (Fig. 4.7) allows the selection of pre-assembled scripts bundled with Stellarium that
can be run (See chapter 16 for an introduction to the scripting capabilities and language). This list
can be expanded by your own scripts as required. See section 5.2 where to store your own scripts.
When a script is selected it can be run by pressing the arrow button and stopped with the stop
button. With some scripts the stop button is inhibited until the script is finished.
Scripts that use sound or embedded videos will need a version of Stellarium configured at

Chapter 4. The User Interface


Figure 4.9: View Settings Window: Sky Tab
compile time with multimedia support enabled. It must be pointed out here that sound or video
codecs available depends on the sound and video capabilities of you computer platform and may
not work.

The Plugins Tab
Plugins (see chapter 11 for an introduction) can be enabled here (Fig. 4.8) to be loaded the next
time you start Stellarium. When loaded, many plugins allow additional configuration which is
available by pressing the configure button on this tab.


The View Settings Window
The View settings window controls many display features of Stellarium which are not available via
the main toolbar.


The Sky Tab
The Sky tab of the View window (Fig. 4.9) contains settings for changing the general appearance of
the main sky view. Some hightlights:
Absolute scale is the size of stars as rendered by Stellarium. If you increase this value, all stars
will appear larger than before.
Relative scale determines the difference in size of bright stars compared to faint stars. Values
higher than 1.00 will make the brightest stars appear much larger than they do in the sky.
This is useful for creating star charts, or when learning the basic constellations.

4.4 The View Settings Window


Twinkle controls how much the stars twinkle when atmosphere is enabled (scintillation, see
section 18.13.2). Since v0.15.0, the twinkling is reduced in higher altitudes, where the star
light passes the atmosphere in a steeper angle and is less distorted.
Limit magnitude Inhibits automatic addition of fainter stars when zooming in. This may be
helpful if you are interested in naked eye stars only.
Dynamic eye adaptation When enabled this feature reduces the brightness of faint objects when
a bright object is in the field of view. This simulates how the eye can be dazzled by a bright
object such as the moon, making it harder to see faint stars and galaxies.
Light pollution In urban and suburban areas, the sky is brightned by terrestrial light pollution
reflected in the atmophere. Stellarium simulates light pollution and is calibrated to the Bortle
Dark Sky Scale where 1 means a good dark sky, and 9 is a very badly light-polluted sky. See
Appendix B for more information.
Solar System objects this group of options lets you turn on and off various features related to
the planets. Simulation of light speed will give more precise positions for planetary bodies
which move rapidly against backround stars (e.g. the moons of Jupiter). The Scale Moon
option will increase the apparent size of the moon in the sky, which can be nice for wide
field of view shots.
Labels and markers you can independantly change the amount of labels displayed for planets,
stars and nebulae. The further to the right the sliders are set, the more labels you will see.
Note that more labels will also appear as you zoom in.
Shooting stars Stellarium has a simple meteor simulation option. This setting controls how many
shooting stars will be shown. Note that shooting stars are only visible when the time rate is 1,
and might not be visiable at some times of day. Meteor showers are not currently simulated.
Atmosphere settings
An auxiliary dialog contains detail settings for the atmosphere. Here you can set atmospheric
pressure and temperature which influence refraction (see section 18.13.2), and the opacity factor kv
for extinction, magnitude loss per airmass (see section 18.13.1).

The Deep-Sky Objects (DSO) Tab
Deep-sky objects or DSO are extended objects which are external to the solar system, and are not
point sources like stars. DSO include galaxies, planetary nebulae and star clusters. These objects
may or may not have images associated with them. Stellarium comes with a catalogue of over
90,000 extended objects containing the combined data from many catalogues, with 200 images.
The DSO tab (Fig. 4.10) allows you to specify which catalogs or which object types you are
interested in. This selection will also be respected in other parts of the program, most notably
Search (section 4.5) and AstroCalc/WUT (section 4.6.6) will not find objects from catalogs which
you have not selected here.
See chapter 8 for details about the catalog, and how to extend it with your own photographs.


The Markings Tab
The Markings tab of the View window (Fig. 4.11) controls the following features:
Celestial sphere this group of options makes it possible to plot various grids and lines in the main
Projection Selecting items in this list changes the projection method which Stellarium uses to
draw the sky (Snyder, 1987). Options are:
Perspective Perspective projection maps the horizon and other great circles like equator,
ecliptic, hour lines, etc. into straight lines. The maximum field of view is 150◦ . The
mathematical name for this projection method is gnomonic projection.


Chapter 4. The User Interface

Figure 4.10: View Settings Window: DSO Tab

Stereographic Stereographic projection has been known since antiquity and was originally
known as the planisphere projection. It preserves the angles at which curves cross each
other but it does not preserve area. Else it is similar to fish-eye projection mode. The
maximum field of view in this mode is 235◦ .
Fish-Eye Stellarium draws the sky using azimuthal equidistant projection. In fish-eye
projection, straight lines become curves when they appear a large angular distance
from the centre of the field of view (like the distortions seen with very wide angle
camera lenses). This is more pronounced as the user zooms out. The maximum field
of view in this mode is 180◦ .
Orthographic Orthographic projection is related to perspective projection, but the point of
perspective is set to an infinite distance. The maximum field of view is 180◦ .
Equal Area The full name of this projection method is Lambert azimuthal equal-area
projection. It preserves the area but not the angle. The maximum field of view is 360◦ .
Hammer-Aitoff The Hammer projection is an equal-area map projection, described by
E RNST VON H AMMER (1858–1925) in 1892 and directly inspired by the Aitoff
projection. The maximum field of view in this mode is 360◦ .
Sinusoidal The sinusoidal projection is a pseudocylindrical equal-area map projection,
sometimes called the Sanson–Flamsteed or the Mercator equal-area projection. Meridians are mapped to sine curves.
Mercator Mercator projection is a cylindrical projection developed by G ERARDUS M ER CATOR (1512–1594) which preserves the angles between objects, and the scale around
an object is the same in all directions. The poles are mapped to infinity. The maximum
field of view in this mode is 233◦ .
Miller cylindrical The Miller cylindrical projection is a modified Mercator projection,
proposed by O SBORN M AITLAND M ILLER (1897–1979) in 1942. The poles are no
longer mapped to infinity.
Cylinder The full name of this simple projection mode is cylindrical equidistant projection
or Plate Carrée. The maximum field of view in this mode is 233◦ .

4.4 The View Settings Window


Figure 4.11: View Settings Window: Markings Tab

The Landscape Tab
The Landscape tab of the View window (Fig. 4.12) controls the landscape graphics (the horizon
which surrounds you). To change the landscape graphics, select a landscape from the list on the left
side of the window. A description of the landscape will be shown on the right.
Note that while a landscape can include information about where the landscape graphics were
taken (planet, longitude, latitude and altitude), this location does not have to be the same as the
location selected in the Location window, although you can set up Stellarium such that selection of
a new landscape will alter the location for you.
The controls at the bottom right of the window operate as follows:
Show ground This turns on and off landscape rendering (same as the button
in the main
Show_fog This turns on and off rendering of a band of fog/haze along the horizon, when available
in this landscape.
Use associated planet and position When enabled, selecting a new landscape will automatically
update the observer location.
Use this landscape as default Selecting this option will save the landscape into the program
configuration file so that the current landscape will be the one used when Stellarium starts.
Minimal brightness Use some minimal brightness setting. Moonless night on very dark locations
may appear too dark on your screen. You may want to configure some minimal brightness
from landscape, if given Landscape authors may decide to provide such a minimal brightness
value in the landscape.ini file.

Chapter 4. The User Interface


Figure 4.12: View Settings Window: Landscape Tab



Show landscape labels Landscapes can be configured with a gazetteer of interesting points, e.g.,
mountain peaks, which can be labeled with this option.
Show illumination to reflect the ugly developments of our civilisation, landscapes can be configured with a layer of light pollution, e.g., streetlamps, bright windows, or the sky glow of a
nearby city. This layer, if present, will be mixed in when it is dark enough.
Using the button Add/remove landscapes. . . , you can also install new landscapes from ZIP files
which you can download e.g. from the Stellarium website2 or create yourself (see ch. 7 Landscapes),
or remove these custom landscapes.
Loading large landscapes may take several seconds. If you like to switch rapidly between
several landscapes and have enough memory, you can increase the default cache size to keep more
landscapes loaded previously available in memory. Note that a large landscape can take up 200MB
or more! See section D.1.11.
The Starlore Tab
The Starlore tab of the View window (Fig. 4.13) controls what culture’s constellations and bright
star names will be used in the main display. Some cultures have constellation art (e.g., Western and
Inuit), and the rest do not. Configurable options include
Use this skyculture as default Activate this option to load this skyculture when Stellarium starts.
Show labels Activate display of constellation labels, like
or V . You can further select
whether you want to display abbreviated, original or translated names.

4.4 The View Settings Window


Figure 4.13: View Settings Window: Starlore Tab
Show lines with thickness. . . Activate display of stick figures, like
or C , and you can
configure constellation line thickness here.
Show asterism lines. . . Activate display of asterism stick figures (like the shortcut Alt + A ), and
you can configure asterism line thickness here.
Show ray helpers. . . Activate display of special navigational lines which connect stars often from
different constellations (like the shortcut Alt + R ), and you can configure thickness of those
lines here.
Show boundaries Activate display of constellation boundaries, like B . Currently, boundaries
have been defined only for “Western” skycultures.
Use native names for planets If provided, show the planet names as used in this skyculture (also
shows modern planet name for reference).
Show art in brightness. . . Activate display of constellation art (if available), like
You can also select the brightness here.
Show asterism labels Activate display of asterism labels, like Alt + V .



or R .

The Surveys Tab
The Surveys tab (Fig. 4.14) allows to toggle the visibility of online sky or solar system surveys (see
chapter 10 for description of the surveys format). Currently, only HiPS surveys are supported.
On the left side of the window we see the list of available surveys from the configured sources
(See section D.1.27 for how to change the default sources). On the right side a description of the
selected survey and its properties are displayed.
Surveys are grouped by types. The top combobox allows to filter the listed surveys according


Chapter 4. The User Interface


Figure 4.14: View Settings Window: Surveys Tab
to a given type (Deep Sky or Solar System).
You can toggle the visibility of a survey by checking the box on the left of the survey name
in the list. (Note that as of v0.18.0, only a single deep sky survey can be rendered at a time, so it
makes no sense to select more than one in the list!) Once a survey is visible you should be able to
see its loading status in the loading bar area of the sky view.
Deep sky surveys will be rendered aligned with the sky view, while solar system surveys
automatically map on the proper body.


The Object Search Window
The Object Search window provides a convenient way to locate objects in the sky. Simply type in
the name of an object to find, and press
. Stellarium will point you at that object in the sky.
As you type, Stellarium will make a list of objects which contains what you have typed so far.
key, the selection
The first of the list of matching objects will be highlighted. If you press the
will change to the next item in the list. Hitting the
key will go to the currently highlighted
object and close the search dialog.
For example, suppose we want to locate Saturn’s moon Mimas. Type the first letter of the name,
m, to see a list of objects whose name contains m: Haumea, Miranda, Umbriel, . . .
You may want at this point to have Stellarium rather propose object names with start with the
string you enter. Do that in the Options tab of this panel. Now repeat searching (delete, and re-enter

4.5 The Object Search Window

Figure 4.15: The Search Window: Objects

Figure 4.16: The Search Window: Positions

Figure 4.17: The Search Window: Lists



Chapter 4. The User Interface

Figure 4.18: The Search Window: Options
m to start over). Now the list is shorter and contains only objects which start with m: Maia, Mars,
. . . The first item in this list, Maia, is highlighted. Pressing
now would go to Maia, but we
want Mimas. We can either press
a few times to highlight Mimas and then hit
, or we can
continue to type the name until it is the first/only object in the list.
The Position tab (Fig. 4.16) provides a convenient way to enter a set of coordinates.
The List Search tab (Fig. 4.18) allows selection of an object from predefined sets. The number
of choices is governed by the loaded DSO catalogs and plug-ins. Scroll down the first window to
select the type. Click on the name and Stellarium will go to that object.
The Options tab (Fig. 4.18) provides a few settings to fine-tune your search experience. When
the name of an object to find is typed in the object window and you are connected to the internet and
“Extend search” is ticked, Stellarium will search the SIMBAD on-line data bases for its coordinates.
You can then click the
button or press return. Stellarium will point you at that object in the sky
even if there is no object displayed on the screen. The SIMBAD server being used can be selected
from the scroll window.


The Astronomical Calculations Window
This window provides advanced functionality, some of which is still in an experimental phase.
You can call it by pressing F10 or the button
on the left menu bar. The Astronomical
Calculations window shows six tabs with different functionality.



The Positions Tab
This tab shows J2000.0 or horizontal positions, magnitudes and additional parameters (e.g. surface
brightness for deep-sky objects or angular separation for double stars) for various lists of celestial
objects above the horizon at the simulated time, filtered by magnitude. Double-clicking on an entry
brings the object into focus (Figure 4.19). You may also export the list of positions into a CSV file.
The Ephemeris Tab
Select an object, start and end time, and compute an ephemeris (list of positions and magnitudes
evolving over time) for that object. The positions are marked in the sky with yellow circles
(Figure 4.20).

4.6 The Astronomical Calculations Window


Figure 4.19: Astronomical Calculations (AstroCalc): Celestial positions

Figure 4.20: Astronomical Calculations (AstroCalc): Plot trace of planet
When you click on a date, an orange circle indicates this date and/or magnitude. Doubleclicking sets the respective date and brings the object to focus. Dates and/or magnitudes will show
near position markers when Show dates and/or Show magnitudes checkboxes are active.
You can export the calculated ephemeris into a CSV file.
Another interesting option in this tool: using horizontal coordinates for plotting traces of the
Solar system objects. In this mode, the circle marks are not linked to the sky, but to the horizontal
coordinate system. For example, you can get an analemma of the Sun for any location (Figures 4.21
and 4.22), or observe the visibility of Mercury, Venus or a comet in the twilight sky.


Chapter 4. The User Interface

Figure 4.21: Astronomical Calculations (AstroCalc): Analemma on the Earth

Figure 4.22: Astronomical Calculations (AstroCalc): Analemma on Mars

4.6 The Astronomical Calculations Window


The Phenomena Tab
This tab allows you to compute phenomena like conjunctions, oppositions, occultations and eclipses
(in special cases) between planetary objects (Figure 4.23). You can export the calculated phenomena
into a CSV file.

Figure 4.23: Astronomical Calculations (AstroCalc): Phenomena


The “Altitude vs. Time” Tab
On this tab you can compute the geometrical altitude of the currently selected object and date and
draw it as a graph (Figure 4.24).

Figure 4.24: Astronomical Calculations (AstroCalc): Altitude vs. Time

Chapter 4. The User Interface


The Graphs Tab

Figure 4.25: Astronomical Calculations (AstroCalc): Graphs


This tab can show two functions over time for the current year and draw graphs for them in one
screen (Figure 4.25). You can select from
• Magnitude vs. Time
• Phase vs. Time
• Distance vs. Time
• Elongation vs. Time
• Angular size vs. Time
• Phase angle vs. Time
This tool may be very helpful for educational and statistics purposes.3
The “What’s Up Tonight” (WUT) Tab
The “What’s Up Tonight” (WUT) tool4 displays a list of objects that will be visible at night for the
current date and location.
The objects are organized into type categories. Select an object type in the box labeled Select
a Category, and all objects of that type which are above the horizon on the selected night will be
displayed in the box labeled Matching Objects. For example, in the screenshot, the Planets category
has been selected, and three planets which are up in the selected night are displayed (Jupiter, Mars
and Mercury).
By default, the WUT will display objects which are above the horizon between sunset and
midnight (i.e. in the evening). You can choose to show objects which are up between midnight and
dawn (in the morning), around midnight, or any time between dusk and dawn (any time tonight)
using the combobox near the top of the window. You can also choose to see only those objects
that are brighter than a certain magnitude by setting a minimum magnitude using the Show objects
brighter than magnitude spinbox. You may center an object from the right list in the sky map just
by selecting it.
Note that only DSO from catalogs which you have selected in the DSO panel (section 4.4.2)
will be found.
3 The
4 This

idea for this tool has been obtained from SkytechX:
tool has been partially ported from the KStars planetarium:

4.6 The Astronomical Calculations Window


Figure 4.26: Astronomical Calculations (AstroCalc): What’s Up Tonight (WUT)

The “Planetary Calculator” (PC) Tab
The “Planetary Calculator” (PC) tool has been added after user requests. It computes the relations
between two Solar system bodies for the current date and location — linear and angular distances,
orbital resonances and orbital velocities.

Figure 4.27: Astronomical Calculations (AstroCalc): Planetary Calculator (PC)




Chapter 4. The User Interface

Help Window

Figure 4.28: Help Window
The Help window lists all of Stellarium’s keystrokes. Note that some features are only available as
keystrokes, so it’s a good idea to have a browse of the information in this window.

Editing Keyboard Shortcuts
You can edit the shortcut keys here. Each available function can be configured with up to two key
combinations. You may want to reconfigure keys for example if you have a non-English keyboard
layout and some keys either do not work at all, or feel unintuitive for you, or if you are familiar with
other software and want to use the same hotkeys for similar functions. Simply select the function
and click with the mouse into the edit field, then press your key of choice. If the key has been taken
already, a message will tell you.
The About Tab (Fig. 4.29) shows version and licensing information, and a list of people who
helped to produce the program.
The Log Tab (Fig. 4.30) shows messages like the loading confirmations carried out when
stellarium runs. It is useful to locate the files that stellarium writes to your computer. The same
information is written to the file log.txt that you will find in your user directory (see 5.1).

4.7 Help Window


Figure 4.29: Help Window: About

Figure 4.30: Help Window: Logfile


Advanced Use


Files and Directories . . . . . . . . . . . . . . . . . . . . . . 45


Directory Structure
The Logfile
The Main Configuration File
Getting Extra Data


Command Line Options . . . . . . . . . . . . . . . . . . . 51


Special Options


Landscapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55


Stellarium Landscapes
Creating Panorama Photographs for Stellarium
Panorama Postprocessing
Other recommended software


Deep-Sky Objects . . . . . . . . . . . . . . . . . . . . . . . . 79


Stellarium DSO Catalog
Adding Extra Nebulae Images


Adding Sky Cultures . . . . . . . . . . . . . . . . . . . . . . 89


Basic Information
Skyculture Description Files
Constellation Names
Star Names
Planet Names
Deep-Sky Objects Names
Stick Figures
Constellation Boundaries
Constellation Artwork
Seasonal Rules
Asterisms and help rays
Publish Your Work

10 Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hipslist file and default surveys
Solar system HiPS survey


5. Files and Directories


Stellarium has many data files containing such things as star catalogue data, nebula images, button
icons, font files and configuration files. When Stellarium looks for a file, it looks in two places.
First, it looks in the user directory for the account which is running Stellarium. If the file is not
found there, Stellarium looks in the installation directory1 . Thus it is possible for Stellarium to be
installed by an administrative user and yet have a writable configuration file for non-administrative
users. Another benefit of this method is on multi-user systems: Stellarium can be installed by
the administrator, and different users can maintain their own configuration and other files in their
personal user accounts.
In addition to the main search path, Stellarium saves some files in other locations, for example
screens shots and recorded scripts.
The locations of the user directory, installation directory, screenshot save directory and script
save directory vary according to the operating system and installation options used. The following
sections describe the locations for various operating systems.


installation directory By default this is C:\Program Files\Stellarium\, although this can
be adjusted during the installation process.
user directory This is the Stellarium sub-folder in the Application Data folder for the user account
which is used to run Stellarium. Depending on the version of Windows and its configuration,
this could be any of the following (each of these is tried, if it fails, the next in the list if tried).
% APPDATA %\ Stellarium \
% USERPROFILE %\ Stellarium \
% HOMEDRIVE %\% HOMEPATH %\ Stellarium \
% HOME %\ Stellarium \
Stellarium ’ s installation directory
1 The

installation directory was referred to as the config root directory in previous versions of this guide

Chapter 5. Files and Directories


Thus, on a typical Windows Vista/7/10 system with user “Bob Dobbs”, the user directory
will be:
C :\ Users \ Bob Dobbs \ AppData \ Roaming \ Stellarium \
The user data directory is unfortunately hidden by default. To make it accessible in the Windows file explorer, open an Explorer window and select Organize... Folder and search options .
Make sure folders marked as hidden are now displayed. Also, deselect the checkbox to “hide
known file name endings”.2
screenshot save directory Screenshots will be saved to the Pictures/Stellarium directory,
although this can be changed in the GUI (see section 4.3.4) or with a command line option
(see section 6).

Mac OS X
installation directory This is found inside the application bundle, See Inside
Application Bundles3 for more information.
user directory This is the sub-directory Library/Preferences/Stellarium/ (or
~/Library/Application Support/Stellarium on newest versions of Mac OS X) of
the user’s home directory.
screenshot save directory Screenshots are saved to the user’s Desktop.


installation directory This is in the share/stellarium sub-directory of the installation prefix,
i.e., usually /usr/share/stellarium or /usr/local/share/stellarium/.
user directory This is the .stellarium sub-directory of user’s home directory, i.e., ~/.stellarium/.
This is a hidden folder, so if you are using a graphical file browser, you may want to change
its settings to “display hidden folders”.
screenshot save directory Screenshots are saved to the user’s home directory.


Directory Structure
Within the installation directory and user directory defined in section 5.1, files are arranged in the
following sub-directories.
landscapes/ contains data files and textures used for Stellarium’s various landscapes. Each
landscape has its own sub-directory. The name of this sub-directory is called the landscape
ID, which is used to specify the default landscape in the main configuration file, or in script
skycultures/ contains constellations, common star names and constellation artwork for Stellarium’s many sky cultures. Each culture has its own sub-directory in the skycultures
nebulae/ contains data and image files for nebula textures. In the future Stellarium may be able
to support multiple sets of nebula images and switch between them at runtime. This feature
is not implemented for version 0.18.0, although the directory structure is in place - each set
of nebula textures has its own sub-directory in the nebulae directory.
2 This

is a very confusing default setting and in fact a security risk: Consider you receive an email
with some file funny.png.exe attached. Your explorer displays this as funny.png. You double-click it,
expecting to open some image browser with a funny image. However, you start some unknown program
instead, and running this .exe executable program may turn out to be anything but funny!

5.3 The Logfile


stars/ contains Stellarium’s star catalogues. In the future Stellarium may be able to support
multiple star catalogues and switch between them at runtime. This feature is not implemented
for version 0.18.0, although the directory structure is in place – each star catalogue has its
own sub-directory in the stars directory.
data/ contains miscellaneous data files including fonts, solar system data, city locations, etc.
textures/ contains miscellaneous texture files, such as the graphics for the toolbar buttons, planet
texture maps, etc.
ephem/ (optional) may contain data files for planetary ephemerides DE430 and DE431 (see 5.5.3).
If any file exists in both the installation directory and user directory, the version in the user
directory will be used. Thus it is possible to override settings which are part of the main Stellarium
installation by copying the relevant file to the user area and modifying it there.
It is recommended to add new landscapes or sky cultures by creating the relevant files and
directories within the user directory, leaving the installation directory unchanged. In this manner
different users on a multi-user system can customise Stellarium without affecting the other users,
and updating Stellarium will not risk the loss of your own data.


The Logfile
Stellarium reports various events and confirmations to a logfile, log.txt, in the user directory.
This has the same content as you can see on the console on Linux when you start Stellarium on the
command line. Normally you don’t need to bother with its contents, however, if Stellarium behaves
unexpectedly, crashes, or shows other problems, a quick look into this file may help to identify the
problem. Also when you report a problem to the developers in the hope that they (we) can ’fix’
anything, this logfile is an essential ingredient to your report. The logfile can also be displayed
within the program: press F1 to call the help panel, and select the Logfile tab.


The Main Configuration File
The main configuration file is read each time Stellarium starts, and settings such as the observer’s
location and display preferences are taken from it. Ideally this mechanism should be totally
transparent to the user – anything that is configurable should be configured “in” the program GUI.
However, at time of writing Stellarium isn’t quite complete in this respect, despite improvements in
each version. Some settings, esp. color values for lines, grids, etc. can only be changed by directly
editing the configuration file.4 This section describes some of the settings a user may wish to
modify in this way, and how to do it.
If the configuration file does not exist in the user directory when Stellarium is started (e.g., the
first time the user starts the program), one will be created with default values for all settings (refer
to section 5 Files and Directories for the location of the user directory on your operating system).
The name of the configuration file is config.ini5 .
The configuration file is a regular text file, so all you need to edit it is a text editor like Notepad
on Windows, Text Edit on the Mac, or nano/vi/gedit/emacs/leafpad etc. on Linux.
A complete list of configuration file options and values may be found in appendix D.1 Configuration File.
4 Color

values can be edited interactively by the Text User Interface plugin (see 12.6).
is possible to specify a different name for the main configuration file using the --config-file
command line option. See section 6 Command Line Options for details.
5 It

Chapter 5. Files and Directories



Getting Extra Data


More Stars
Stellarium is packaged with over 600 thousand stars in the normal program download, but much
larger star catalogues may be downloaded in the Tools tab of the Configuration dialog (


5.5.2 More Deep-Sky Objects
Stellarium is packaged with over 90 thousand deep-sky objects6 in the normal program download
(the standard edition of Stellarium DSO catalog, see section 8.1), but an extended DSO catalog
with over one million objects (up to 19.0m ) may be downloaded from Stellarium’s SourceForge
website7 :
MD5 hash
3.3; extended edition catalog.dat b703354655d7d7f109f2ed97100b8de5 28.6 MB
The file can be placed in a folder named nebulae/default inside either the installation
directory (replacing of standard catalog) or the user directory (see section 5.2).
5.5.3 Alternative Planet Ephemerides: DE430, DE431
By default, Stellarium uses the VSOP87 planetary theory, an analytical solution which is able to
deliver planetary positions for any input date (P. Bretagnon and Francou, 1988). However, its use is
recommended only for the year range −4000 . . . + 8000. Outside this range, it seems to be usable
for a few more millennia without too great errors, but with degrading accuracy. Likewise for the
moon, Stellarium by default uses ELP 2000-82B (Chapront-Touze, 1982; Chapront-Touzé and
Chapront, 1983; Chapront-Touzé and Chapront, 1988b).
Since v0.15.0 you can install extra data files which allow access to the numerical integration runs
DE430 and DE431 from NASA’s Jet Propulsion Laboratory (JPL) (Folkner et al., 2014). The data
files have to be downloaded separately, and most users will likely not need them. DE430 provides
highly accurate data for the years +1550 . . . + 2650, while DE431 covers years −13000 . . . + 17000,
which allows e.g. archaeoastronomical research on Mesolithic landscapes. Outside these year
ranges, positional computation falls back to VSOP87.
The integration of this feature is still somewhat experimental, and some other current approximations will lead to numerical data which differ slightly from best possible ephemerides. Please at
least compare with JPL Horizons8 for dependable results.
To enable use of these data, download the files from JPL9 :
Ephemeris Filename
MD5 hash
linux_p1550p2650.430 707c4262533d52d59abaaaa5e69c5738 97.5 MB
fad0f432ae18c330f9e14915fbf8960a 2.59 GB
The files can be placed in a folder named ephem inside either the installation directory or the
user directory (see 5.2). Alternatively, if you have them already stored elsewhere, you may add the
path to config.ini like:

6 Over

83 thousand deep-sky objects in version 0.16.0.


are not running Linux!)

(Also download from this directory if you

5.5 Getting Extra Data


[ astro ]
de430_path = C :/ Astrodata / JPL_DE43x / linux_p1550p2650 .430
de431_path = C :/ Astrodata / JPL_DE43x / lnxm13000p17000 .431
For fast access avoid storing them on a network drive or USB pendrive!
You activate use of either ephemeris in the Configuration panel ( F2 ). If you activate both,
preference will be given for DE430 if the simulation time allows it. Outside of the valid times,
VSOP87 will always be used.
The optional use of DE430/431 has been supported by the ESA Summer of Code in Space 2015

GPS Position
In the Location panel (see section 4.2) you can receive your location from a GPS device. The exact
way to receive GPS location depends on your operating system.
GPSD (Linux, Mac OS X only)
On Linux, Mac-OS X and other Unixoid platforms, Stellarium preferrably should not connect
directly to a GPS USB device, serial device, bluetooth device, etc., but uses a connection to the
gpsd daemon running on a computer in your network which provides GPS services concurrently for
any interested application. In most cases, this will be a gpsd running on your localhost, receiving
data from some GPS device plugged in via USB.
Please follow instructions by the gpsd authors10 to properly configure this system daemon. A
few hints:
• On Ubuntu 16.04 and likely other systems, USB hotplug devices are handled by the udev
daemon which detects newly plugged-in devices and creates device files in the /dev directory. Unfortunately, most GPS devices use the Prolific 2303 chipset in their serial-toUSB converter and are identified as such, without other unique information like serial
numbers. This chipset is also used in other Serial-to-USB converter cables, and to avoid
conflicts the according rule has been disabled by the release managers of Ubuntu. In
/lib/udev/60-gpsd.rules, find the commented line and re-activate it.
• If you have such an USB GPS mouse and USB-to-serial converters for other purposes like
for your telescope control, you must solve the “udev crisis” in some other way to get gpsd
running. You may be able to find some property in your device to uniquely identify this
device and write an udev rule to create the symlink in /dev/gps0 to which gpsd can then
• You can also connect to another computer which runs gpsd. This could be a little Raspberry
Pi computer which happens to be in your WiFi to allow localisation and time service. To
configure this, you must manually edit config.ini. Find the [gui] section and edit
[ gui ]
# These values are used on non - Windows systems
# supporting GPSD
= " localhost "
= 2947
Also, gpsd must be started with the -G parameter to enable this.


Chapter 5. Files and Directories


• Even your smartphone can be used as GPS data source11 : Apps like BlueNMEA can provide
these data for gpsd, but you must make sure to configure hostname/IP Address and port
number correctly, for example
sudo gpsd -n - D8 -S 1001 tcp ://
which means
-n to start without a device connection
-D8 maximum debug level. When it works, use what suits you
-S 1001 provide service on port 1001
tcp Use this address:port combination to receive data from (IP of your smartphone, port
shown on BlueNMEA screen).
• In case you really don’t want to use the gpsd, you can use a directly connected device, see
below. This is however not recommended when you have gpsd available.
NMEA Device
This mode is primarily for Windows users, but also for Linux and Mac users who don’t want to use
Virtually all GPS receivers are able to emit the standardized NMEA-0183 messages which
encode time, position, speed, satellite information and other data. The standard originally required
connection settings of 4800 baud, 8 bit, no parity, one stop bit (8N1), however some devices come
with faster transfer.
Compatible devices today are connected on a “virtual COM port” via USB. Unfortunately the
COM number seems to depend on the USB plug where you attach the receiver. You can identify
the port name (COM3, COM4, . . . ) in the Windows system configuration (Device Manager) or
with the software that came with your device.12
If this is the only serial device, Stellarium should automatically connect to it regardless of
configuration entries. You cannot change the USB plug after you first have received a location
fix. If you have a device with non-standard baudrate or several serial devices on serial ports (e.g.,
your telescope?), you must find out which serial port is used by the GPS device and manually edit
config.ini. Find the [gui] section and edit
[ gui ]
# These values are used on Windows primarily .
= " COM3 "
= 4800
From now on, always use the same USB plug configuration to connect GPS and telescope.13 If
GPS lookup fails, see the logfile for diagnostic messages.
Bluetooth GPS
Most smartphones provide GPS and Bluetooth hardware. You can install a virtual COM port in
your Windows Bluetooth settings and use a smartphone app like BlueNMEA to provide the NMEA

11 Thanks

to user Caysho for this hint.
Linux, this may read /dev/ttyUSB0, /dev/gps0 or similar.
13 Again, for Linux the port number is defined in order of hotplugging by udev. You should develop an
udev rule which adds a unique name and use this. In this case, you may also need to add your user to the
dialout group (or whichever group owns your serial port). Better yet, use gpsd (see above).
12 On

6. Command Line Options

Stellarium’s behaviour can be modified by providing parameters to the program when it is called
via the command line. See table for a full list:

Option Parameter


--help or -h


Print a quick command line help message,
and exit.

--version or -v


Print the program name and version information, and exit.

--config-file or -c

config file name

Specify the configuration file name. The default value is config.ini.
The parameter can be a full path (which will
be used verbatim) or a partial path.
Partial paths will be searched for inside the
regular search paths unless they start with a
“.”, which may be used to explicitly specify
a file in the current directory or similar.
For example, using the option -c
my_config.ini would resolve to the
file /my_config.ini
whereas -c ./my_config.ini can be used
to explicitly say the file my_config.ini in
the current working directory.



Stellarium will start with the default configuration. Note: The old configuration file will
be overwritten.



Specify the user data directory.

Chapter 6. Command Line Options



Specify the directory to which screenshots
will be saved.


yes or no

Over-rides the full screen setting in the config



Specify observer planet (English name).
Specify latitude, e.g. +53d58’16.65"
Specify longitude, e.g. -1d4’27.48"
Specify observer altitude in meters.




landscape ID




script name

Print a list of available landscape IDs and
Start using landscape whose ID matches the
passed parameter (dir name of landscape).
The initial date in yyyymmdd format.
The initial time in hh:mm:ss format.
The name of a script to run after the program
has started. [startup.ssc]



The initial field of view in degrees.




--spout or -S

all or sky

--dump-opengl-details or -d


--angle-mode or -a


--angle-d3d9 or -9






--mesa-mode or -m


--safe-mode or -s
--compat33 or -C


1 On

Windows only
function requires running in OpenGL mode.

2 This



Act as Spout sender (See section 6.2.1).12
Use name as name of the Spout sender. Default name: Stellarium.1
Even more diagnostic output in logfile (esp.
multimedia handling)
Dump information about OpenGL support to
logfile. Use this is you have graphics problems and want to send a bug report.
Use ANGLE as OpenGL ES2 rendering engine (autodetect Direct3D version).1
Force use Direct3D 9 for ANGLE OpenGL
ES2 rendering engine.1
Force use Direct3D 11 for ANGLE OpenGL
ES2 rendering engine.1
Force use the Direct3D 11 software rasterizer
for ANGLE OpenGL ES2 rendering engine.1
Use MESA as software OpenGL rendering
Synonymous to --mesa-mode.1
Request OpenGL 3.3 Compatibility Profile.
May help for certain driver configurations.

6.1 Examples
--fix-text or -t


Alternative way of creating the Info text, required on some systems.3

If you want to avoid adding the same switch every time when you start Stellarium from the
command line, you can also set an environment variable STEL_OPTS with your default options.



• To start Stellarium using the configuration file, configuration_one.ini situated in the
user directory (use either of these):
stellarium -- config - file = configuration_one . ini
stellarium -c configuration_one . ini
• To list the available landscapes, and then start using the landscape with the ID “ocean”
stellarium -- list - landscapes
stellarium -- landscape = ocean
Note that console output (like --list-landscapes) on Windows is not possible.


Special Options


Apart from stand-alone use, Stellarium can be used as multimedia source in larger installations,
in museums or science exhibitions. Spout4 is a technology which enables use of Stellarium’s
output window as texture in DirectX applications on Windows. Simply start Stellarium with the
--spout=sky command line option. (Currently Spout output is limited to the main window without
GUI panels, but this may change in future versions.) Your master application must obviously embed
a Spout receiver. The default name of the Spout sender is Stellarium. If you need more than
one instance of Stellarium acting as source, you can use option --spout-name=StelSpout2 in
addition to create another Spout sender without a name conflict. In such cases, it may be useful to
also have separate user data directories and use option --user-dir.
This mode does not work in ANGLE mode and requires modern graphics hardware with
the WGL_NV_DX_interop driver extension running in OpenGL mode. Some NVidia GPUs work
without this extension listed explicitly. On a notebook with NVidia Optimus technology, make sure
to launch Stellarium on the NVidia hardware. For permanent setting, use the NVidia configuration
dialog to configure Stellarium explicitly to run always on the NVidia card.

3 E.g.,

Raspberry Pi 2/3 with Raspbian Jessie and VC4 drivers from Mesa 11 (2016).



7. Landscapes


Landscapes are one of the key features that make Stellarium popular. Originally just used for
decoration, since version 10.6 they can be configured accurately for research and demonstration in “skyscape astronomy”, a term which describes the connection of landscape and the sky
above (Brown, 2015). Configured properly, they can act as reliable proxies of the real landscapes,
so that you can take e.g. measurements of sunrise or stellar alignments (Zotti and Neubauer, 2015),
or prepare your next moonrise photograph, as though you were on-site.
In this chapter you can find relevant information required to accurately configure Stellarium
landscapes, using panoramas created from photographs taken on-site, optionally supported by
horizon measurements with a theodolite.
Creating an accurate panorama requires some experience with photography and image processing. However, great open-source tools have been developed to help you on the job. If you already
know other tools, you should be able to easily transfer the presented concepts to those other tools.


Stellarium Landscapes
As of version 0.15, the available landscape types are:
polygonal A point list of measured azimuth/altitude pairs, used to define a sharp horizon polygon.
The area below the horizon line is colored in a single color (Section 7.1.2).
spherical The simple form to configure a photo-based panorama: A single image is used as texture
map for the horizon (Section 7.1.3).
old_style The original photo panorama. This is the most difficult to configure, but allows highest
resolution by using several texture maps (Section 7.1.4).
fisheye Another 1-texture approach, utilizing an image made with a fisheye lens. This landscape suffers from calibration uncertainties and can only be recommended for decoration
(Section 7.1.5).
A landscape consists of a landscape.ini plus the data files that are referenced from there,


Chapter 7. Landscapes

like a coordinate list or the textures. Those reside in a subdirectory of the landscape folder inside
the Stellarium program directory, or, for own work, in a subdirectory of the landscape folder
inside your Stellarium user data directory (see section 5.1).
Let us ssume we want to create a landscape for a place called Rosenburg. The location for the
files of our new custom landscape Rosenburg depends on the operating system (see 5.1). Create a
new subdirectory, and for maximum compatibility, use small letters and no spaces:
Windows C:/Users/YOU/AppData/Roaming/Stellarium/landscapes/rosenburg

Location information
This optional section in landscape.ini allows automatic loading of site coordinates if this option
is activated in the program GUI (see 4.4.4). For our purposes we should consider especially the
coordinates in the location section mandatory!
[ location ]
planet = Earth
country = Austria
name = KGA Rosenburg
latitude = +48 d38 ’3.3 "
longitude ␣ = ␣ +15 d38 ’2.8 "
altitude = 266
light_pollution = 1
at mo sp h e r i c _ e x t i n c t i o n _ c o e f f i c i e n t = 0.2
display_fog = 0
atmospheric_tempe rature = 10.0
atmospheric_pressure = 1013.0
planet Is the English name of the solar system body for the landscape.
latitude Is the latitude of site of the landscape in degrees, minutes and seconds. Positive values
represent North of the equator, negative values South of the equator.
longitude Is the longitude of site of the landscape. Positive values represent East of the Greenwich Meridian on Earth (or equivalent on other bodies), Negative values represent Western
altitude Is the altitude of the site of the landscape in meters.
country (optional) Name of the country the location is in.
state (optional) Name of the state the location is in.
name (optional) Name of the location. This may contain spaces, but keep it short to have it fully
visible in the selection box.
Since v0.11.0, there are a few more optional parameters that can be loaded if the according switch
is active in the landscape selection panel. If they are missing, the parameters do not change to
light_pollution (optional) Light pollution of the site, given on the Bortle Scale (1: none . . . 9:
metropolitan; see Appendix B). If negative or absent, no change will be made.
atmospheric_extinction_coefficient (optional, no change if absent.) Extinction coefficient
(mag/airmass) for this site.
atmospheric_temperature (optional, no change if absent.) Surface air temperature (Degrees
Celsius). Used for refraction. Set to -1000 to explicitly declare "no change".

7.1 Stellarium Landscapes


atmospheric_pressure (optional, no change if absent.) Surface air pressure (mbar; would be
1013 for "normal" sea-level conditions). Used for refraction. Set to -2 to declare "no change",
or -1 to compute from altitude.
display_fog (optional, -1/0/1, default=-1) You may want to preconfigure setting 0 for a landscape
on the Moon. Set -1 to declare "no change".

Polygonal landscape
This landscape type has been added only recently (since 0.13) to allow the use of measured horizons.
Users of Cartes du Ciel1 will be happy to hear that the format of the list of measurements is
This is the technically simplest of the landscapes, but may be used to describe accurately
measured horizon lines. The file that encodes horizon altitudes can also be used in all other
landscape types. If present there, it will be used to define object visibility (instead of the opacity of
the landscape photo textures) and, if horizon_line_color is defined, will be plotted.
There is a small caveat: Sometimes, there may appear vertical lines from some corners towards
the zenith or the mathematical horizon, e.g. if there is a vertex including azimuth 0 or 180. If this
irritates you, just offset this azimuth minimally (e.g., 180.00001).
The landscape.ini file for a polygonal type landscape looks like this (this example is based
on the Geneve landscape which was borrowed from Cartes du Ciel and comes with Stellarium):
[ landscape ]
name = Geneve
type = polygonal
author = Georg Zotti ; Horizon definition by Patrick Chevalley
description = Horizon line of Geneve .
Demonstrates compatibility with
horizon descriptions from Cartes du Ciel .
polygonal_horizon_list = horizon_Geneve . txt
polygonal_angle_r otatez = 0
ground_color = .15 ,.45 ,.45
horizon_line_color = .75 ,.45 ,.45
name appears in the landscape tab of the configuration window.
type identifies the method used for this landscape. polygonal in this case.
author lists the author(s) responsible for images and composition.
description gives a short description visible in the selection panel. The text can be superseded
by optional description..utf8 files.
polygonal_horizon_list is the name of the horizon data file for this landscape.
polygonal_horizon_list_mode (optional) the two first columns in the list are numbers: azimuth and altitude or zenith distance, in either degrees or radians or gradians(gon). The value
must be one of azDeg_altDeg, azDeg_zdDeg, azRad_altRad, azRad_zdRad, azGrad_altGrad,
azGrad_zdGrad. Default: azDeg_altDeg
polygonal_angle_rotatez (optional, default=0) Angle (degrees) to adjust azimuth. This may
be used to apply a (usually) small offset rotation, e.g. when you have measured the horizon
in a grid-based coordinate system like UTM and have to compensate for the meridian
1 SkyChart

/ Cartes du Ciel planetarium:

Chapter 7. Landscapes


ground_color (optional, default=0,0,0, i.e., black) Color for the area below the horizon line.
Each R,G,B component is a float within 0..1.
horizon_line_color (optional, default: invisible) used to draw a polygonal horizon line. Each
R,G,B component is a float within 0..1.
minimal_brightness (optional) Some minimum brightness to keep landscape visible. Default=1, i.e., use minimal_brightness from the [landscape] section in the global config.ini.
minimal_altitude (optional, default=-2) Some sky elements, e.g. stars, are not drawn below
this altitude to increase performance. Under certain circumstances you may want to specify
something else here. (since v0.14.0)
polygonal_horizon_inverted (optional, default=false) In rare cases like horizon lines for high
mountain peaks with many negative horizon values this should be set to true. (since v0.15.0)

Spherical landscape
This method uses a more usual type of panorama – the kind which is produced directly from
software such as autostitch or Hugin2 . The Moon landscape which comes with Stellarium
provides a minimal example of a landscape.ini file for a spherical type landscape:
[ landscape ]
name = Moon
type = spherical
maptex = apollo17 . png
A more elaborate example is found with the Grossmugl landscape:
[ landscape ]
name = Grossmugl
type = spherical
author = Guenther Wuchterl , Kuffner - Sternwarte . at ;
Lightscape : Georg Zotti
description = Field near Leeberg , Grossmugl ( Riesentumulus ) ,
Austria - Primary Observing Spot of the Grossmugl
Starlight Oasis - http :// starlightoasis . org
maptex = gros smug l_l eebe rg_c rop1 1 .25. png
maptex_top =11.25
maptex_fog = g r o s s mu g l _ l ee b e r g _ fo g _ c r op 2 2 .5. png
maptex_fog_top = 22.5
maptex_fog_bottom = -22.5
maptex_illum = g r o s s m u g l _l e e b e r g _ i l l u m _ c r o p 0 . png
maptex_illum_bottom = 0
angle_rotatez = -89.1
minimal_brightness = 0.0075
polygonal_horizon_list = horizon_grossmugl . txt
polygonal_angle_r otatez =0
horizon_line_color = .75 ,.45 ,.45
minimal_altitude = -1
name appears in the landscape tab of the configuration window. This name may be translated.
type identifies the method used for this landscape. spherical in this case.

7.1 Stellarium Landscapes


author lists the author(s) responsible for images and composition.
description gives a short description visible in the selection panel. The text will be superseded
by optional description..utf8 files.
maptex is the name of the image file for this landscape.
maptex_top (optional; default=90) is the altitude angle of the top edge.
maptex_bottom (optional; default=-90) is the altitude angle of the bottom edge. Usually you will
not require this, or else there will be a hole at your feet. ;-)
maptex_fog (optional; default: no fog) is the name of the fog image file for this landscape.
maptex_fog_top (optional; default=90) is the altitude angle of the top edge of the fog texture.
Useful to crop away parts of the image to conserve texture memory.
maptex_fog_bottom (optional; default=-90) is the altitude angle of the bottom edge.
maptex_illum (optional; default: no illumination layer) is the name of the nocturnal illumination/light pollution image file for this landscape.
maptex_illum_top (optional; default=90) is the altitude angle of the top edge, if you have light
pollution only close to the horizon.
maptex_illum_bottom (optional; default=-90) is the altitude angle of the bottom edge.
angle_rotatez (optional, default=0) Angle (degrees) to adjust azimuth. If 0, the left/right edge
is due east.
tesselate_rows (optional, default=20) This is the number of rows for the maptex. If straight
vertical edges in your landscape appear broken, try increasing this value, but higher values
require more computing power. Fog and illumination textures will have a similar vertical
tesselate_cols (optional, default=40) If straight horizontal edges in your landscape appear
broken, try increasing.
polygonal_horizon_list (optional) is the name of the (measured) horizon data file for this
landscape. Can be used to define the exact position of the horizon. If missing, the texture
can be queried for horizon transparency (for accurate object rising/setting times)
polygonal_horizon_list_mode (optional) see 7.1.2
polygonal_angle_rotatez (optional, default=0) see 7.1.2
horizon_line_color see 7.1.2
minimal_brightness see 7.1.2
minimal_altitude (optional, default=-2) Some sky elements, e.g. stars, are not drawn below
this altitude for efficiency. Under certain circumstances (e.g. for space station panoramas
where you may have sky below your feet, or for deep valleys/high mountains, you may want
to specify something else here. (since v0.14.0)
To save texture memory, you can trim away the transparent sky and define the angle maptex_top.
Likewise, fogtex_top, fogtex_bottom, maptex_illum_top and maptex_illum_top. You
should then stretch the texture to a full power of 2, like 4096 × 1024 (but note that some hardware
is even limited to 2048 pixels). The easiest method to create perfectly aligned fog and illumination
layers is with an image editor that supports layers like the GIMP or Photoshop. Fog and Light
images should have black background.

High resolution (“Old Style”) landscape
The old_style or multiple image method works by having the 360◦ panorama of the horizon
(without wasting too much texture memory with the sky) split into a number of reasonably small
side textures, and a separate ground texture. This has the advantage over the single-image method
that the detail level of the horizon can be increased without ending up with a single very large image
file, so this is usable for either very high-resolution panoramas or for older hardware with limited
capabilities. The ground texture can be a different resolution than the side textures. Memory usage

Chapter 7. Landscapes


Figure 7.1: Old_style landscape: eight parts delivering a high-resolution panorama. The
bottom (ground) texture, drawn on a flat plane, is not shown here.
may be more efficient because there are no unused texture parts like the corners of the texture file
in the fish-eye method. It is even possible to repeat the horizon several times (for purely decorative
purpose). The side textures are mapped onto curved (spherical ring or cylinder) walls (Fig. 7.1).
On the negative side, it is more difficult to create this type of landscape – merging the ground
texture with the side textures can prove tricky. (Hugin can be used to create also this file, though.
And on the other hand, you can replace this by something else like a site map.) The contents of
the landscape.ini file for this landscape type is also somewhat more complicated than for other
landscape types. Here is the landscape.ini file which describes our Rosenburg landscape3 :
[ landscape ]
name = KGA Rosenburg
author = Georg Zotti , VIAS / ASTROSIM
description = KGA Rosenburg
type = old_style
nbsidetex = 8
tex0 = Horiz -0. png
tex1 = Horiz -1. png
tex2 = Horiz -2. png
tex3 = Horiz -3. png
tex4 = Horiz -4. png
tex5 = Horiz -5. png
tex6 = Horiz -6. png
tex7 = Horiz -7. png
nbside = 8
side0 = tex0 :0:0:1:1
side1 = tex1 :0:0:1:1
side2 = tex2 :0:0:1:1
3 the

groundtex grassground.png mentioned here has been taken from the Guereins landscape.

7.1 Stellarium Landscapes


side3 = tex3 :0:0:1:1
side4 = tex4 :0:0:1:1
side5 = tex5 :0:0:1:1
side6 = tex6 :0:0:1:1
side7 = tex7 :0:0:1:1
groundtex = grassground . png
ground = groundtex :0:0:1:1
nb_decor_repeat = 1
decor_alt_angle = 82
decor_angle_shift = -62
; Rotatez deviates from -90 by the Meridian Convergence .
; The original landscape pano is grid - aligned , not north - aligned !
decor_angle_rotatez = -90.525837223
ground_angle_shift = -62
ground_angle_rotatez = 44.474162777
draw_ground_first = 1
fogtex = fog . png
fog_alt_angle = 20
fog_angle_shift = -3
fog = fogtex :0:0:1:1
calibrated = true
[ location ]
planet = Earth
latitude = +48 d38 ’3.3 "
longitude ␣ = ␣ +15 d38 ’2.8 "
altitude = 266
light_pollution = 1
at mo sp h e r i c _ e x t i n c t i o n _ c o e f f i c i e n t = 0.2
display_fog = 0
atmospheric_tempe rature = 10.0
atmospheric_pressure = 1013.0
name is the name that will appear in the landscape tab of the configuration window for this
type should be old_style for the multiple image method.
author lists the author(s) responsible for images and composition.
description gives a short description visible in the selection panel. The text will be superseded
by optional description..utf8 files.
nbsidetex is the number of side textures for the landscape.
tex0 ... tex are the side texture file names. These should exist in the
textures / landscapes / landscape directory in PNG format.
light0 ... light are optional textures. If they exist, they are used as overlays
on top of the respective tex<...> files and represent nocturnal illumination, e.g. street
lamps, lit windows, red dots on towers, sky glow by city light pollution, . . . Empty (black)
panels can be omitted. They are rendered exactly over the tex<...> files even when the
PNG files have different size. If you need your light pollution higher in the sky, you must
use a spherical or fisheye landscape.
nbside is the number of side textures


Chapter 7. Landscapes



side0 ...side are the descriptions of how the side textures should be arranged in
the program. Each description contains five fields separated by colon characters (:). The
first field is the ID of the texture (e.g. tex0), the remaining fields are the texture coordinates
(x0:y0:x1:y1) used to place the texture in the scene. If you want to use all of the image,
this will just be 0:0:1:1.
groundtex is the name of the ground texture file. (This could also be a diagram e.g. indicating
the mountain peaks!)
fogtex is the name of the texture file for fog in this landscape. Fog is mapped onto a simple
cylinder.4 Note that for this landscape, accurate overlay of fog and landscape is only
guaranteed if calibrated=true and tan_mode=true.
nb_decor_repeat is the number of times to repeat the side textures in the 360 panorama. (Useful
photo panoramas should have 1 here)
decor_alt_angle (degrees) is the vertical angular extent of the textures (i.e. how many degrees
of the full altitude range they span).
decor_angle_shift (degrees) vertical angular offset of the scenery textures, at which height the
bottom line of the side textures is placed.
decor_angle_rotatez (degrees) angular rotation of the panorama around the vertical axis. This
is handy for rotating the landscape so North is in the correct direction. Note that for historical
reasons, a landscape with this value set to zero degrees has its leftmost edge pointing towards
ground_angle_shift (degrees) vertical angular offset of the ground texture, at which height the
ground texture is placed.
ground_angle_rotatez (degrees) angular rotation of the ground texture around the vertical axis.
When the sides are rotated, the ground texture may need to be rotated as well to match up
with the sides.
fog_alt_angle (degrees) vertical angular size of the fog cylinder - how fog looks. Accurate
vertical size requires calibrated=true.
fog_angle_shift (degrees) vertical angular offset of the fog texture - at what height is it drawn.
Accurate vertical placement requires calibrated=true.
draw_ground_first if 1 the ground is drawn in front of the scenery, i.e. the side textures will
overlap over the ground texture.
calibrated (optional). Only if true, decor_alt_angle etc. really work as documented above.
The (buggy) old code was left to work with the landscapes already existing. Note that with
“uncalibrated” landscapes, sunrise computations and similar functionality which requires an
accurate horizon line will not work.
tan_mode (optional, not used in this file). If true, the panorama image must be in in cylindrical,
not equirectangular projection. Finding decor_alt_angle and decor_angle_shift may
be a bit more difficult with this, but now (v0.13.0) works also with calibrated. A fog image
created as overlay on the pano will be perfectly placed.
decor_angle_rotatez angular rotation of the scenery around the vertical axis. This is handy for
rotating the landscape so North is in the correct direction. If 0, the left edge of tex0 is due
ground_angle_shift vertical angular offset of the ground texture, at which height the ground
texture is placed. Values above -10 are not recommended for non-photographic content (e.g.,
a map) due to high distortion.
ground_angle_rotatez angular rotation of the ground texture around the vertical axis. When
the sides are rotated, the ground texture may need to be rotated as well to match up with the
sides. If 0, east is up. if North is up in your image, set this to 90. Note that adjustments of
4 In

very wide-angle views, the fog cylinder may become visible in the corners.

7.1 Stellarium Landscapes


decor_angle_rotatez require adjustments of this angle in the opposite direction!
fog_alt_angle vertical angular size of the fog cylinder.
fog_angle_shift vertical angular offset of the fog cylinder.
draw_ground_first if 1, the ground is drawn before the sides, i.e. the side textures may overlap
the ground texture if ground_angle_shift > decor_angle_shift.
polygonal_horizon_list (optional) see 7.1.2
polygonal_horizon_list_mode (optional) see 7.1.2
polygonal_angle_rotatez (optional, default=0) see 7.1.2
horizon_line_color see 7.1.2
minimal_brightness see 7.1.2
minimal_altitude see 7.1.2

Fisheye landscape
The Trees landscape that is provided with Stellarium is an example of the single fish-eye method,
and provides a good illustration. The centre of the image is the spot directly above the observer
(the zenith). The point below the observer (the nadir) becomes a circle that just touches the edges
of the image. The remaining areas of the image (the corners outside the circle) are not used.
The image file (Fig. 7.2) should be saved in PNG format with alpha transparency. Whereever
the image is transparent Stellarium will render the sky.
The landscape.ini file for a fish-eye type landscape looks like this (this example is based on
the Trees landscape which comes with Stellarium):
[ landscape ]
name = Trees
type = fisheye
author = Robert Spearman . Light pollution image : Georg Zotti
description = Trees in Greenlake Park , Seattle
maptex = trees_512 . png
maptex_illum = trees_illum_512 . png
maptex_fog = trees_fog_512 . png
texturefov = 210
angle_rotatez = 17
tesselate_rows = 28
tesselate_cols = 60
name appears in the landscape tab of the configuration window.
type identifies the method used for this landscape. fisheye in this case.
author lists the author(s) responsible for images and composition.
description gives a short description visible in the selection panel. The text will be superseded
by optional description..utf8 files.
maptex is the name of the image file for this landscape.
maptex_fog (optional) is the name of the fog image file for this landscape.
maptex_illum (optional) is the name of the nocturnal illumination/light pollution image file for
this landscape.
texturefov is the field of view that the image covers in degrees.
angle_rotatez (optional) Angle (degrees) to adjust azimuth.
tesselate_rows (optional, default=20) If straight edges in your landscape appear broken, try


Chapter 7. Landscapes

Figure 7.2: Texture for the Trees Fisheye landscape.
tesselate_cols (optional, default=40) If straight edges in your landscape appear broken, try
polygonal_horizon_list (optional) see 7.1.2
polygonal_horizon_list_mode (optional) see 7.1.2
polygonal_angle_rotatez (optional, default=0) see 7.1.2
horizon_line_color see 7.1.2
minimal_brightness see 7.1.2
minimal_altitude see 7.1.2

The short description entry in landscape.ini will be replaced by the contents of an optional
file description..utf8.  is the ISO 639-1 language code, or its extension which
contains language and country code, like pt_BR for Brazilian Portuguese. The long description
requires the file description.en.utf8, this is en=english text with optional HTML tags for

7.1 Stellarium Landscapes


sections, tables, etc. You can also have embedded images in the HTML (Views of sacred landscapes,
other informative images, . . . ?), just make them PNG format please. The length of the description
texts is not limited, you have room for a good description, links to external resources, whatever
seems suitable.
If you can provide other languages supported by Stellarium, you can provide translations
yourself, else Stellarium translators may translate the English version for you. (It may take years
though.) The file ending .utf8 indicates that for special characters like ÄÖÜßáé you should use
UTF8 encoding. If you write only English/ASCII, this may not be relevant.

An optional feature for landscapes is a gazetteer function, i.e., labels for landscape features. The
Grossmugl landscape demonstrates an example and should be self-explanatory. This is again
multilingual, so the files are called gazetteer..utf8.
# demo gazetteer for Grossmugl landscape .
# Can be used to better describe the landscape ,
# i . e . show labels on landscape features .
# Fields must be separated by vertical line ,
# label must not have such a vertical line .
# Comments have this hash mark in first column .
# coordinates in degrees from true North .
# line towards zenith draws a single line strictly upward .
# label is centered on line endpoint .
# Azimuth | Altitude | degrees
| azimuth | label
| towards zenith | shift |
| 5.5
| Leeberg
| 1.5
| Grossmugl
| 2
| Steinabrunn
| 2
| Ringendorf
| 2
| Vienna (30 km )
| 2
| Wind power plant Strasshof


Packing and Publishing
You likely have developed your landscape already in your own Stellarium user data directory,
but when you are happy with your work, you may consider sharing it with other users. For easy
distribution and installation via Stellarium’s GUI (see section 4.4.4), you should create a ZIP
file. This must contain landscape.ini and any textures and auxiliary files described above
(description.en.utf8, gazetteer.en.utf8 and their translations, horizon files, images for
the description . . . ) used by your landscape. If you want to release the landscape for download,
consider adding a README.txt clarifying license and usage conditions. It does not matter whether
the ZIP file contains a directory name inside the ZIP. If not, the directory name (ID) of the landscape
will be taken from the ZIP file name.


Chapter 7. Landscapes


Figure 7.3: Zenit “Horizon 202” panorama camera with rotating lens for 35mm film.
(Source: Wikipedia, “Horizon202” by BillC - Own Work. Licensed under CC BY-SA 3.0 via Wikimedia
Commons -


Creating Panorama Photographs for Stellarium


Panorama Photography
Traditional film-based panorama photography required dedicated cameras with curved film holders
and specialized lenses (Figure 7.3).
Digital photography has brought a revolution also in this field, and it has become quite easy to
create panoramas simply by taking a series of photographs with a regular camera on the same spot
and combining them with dedicated software.
A complete panorama photo visually encloses the observer like the mental image that astronomers have been using for millennia: the celestial sphere. If we want to document the view,
say, in a big hall like a church, optimal results will be gained with a camera on a tripod with a
specialized panorama head (Figure 7.4) which assures the camera rotates around the entrance
pupil5 of the lens in order to avoid errors by the parallax shift observed on photographs taken on
adjacent but separate positions.
Often however, both the upper half of the observer’s environment (the sky) and the ground
the photographer is standing on, are regarded of lesser importance, and only a series of laterally
adjacent photographs is taken and combined into a cylindrical or spherical ring that shows the
landscape horizon, i.e., where ground and sky meet. If the closest object of interest is farther
away that a few metres, requirements on parallax avoidance are far less critical, and the author has
taken lots of landscape panoramas with a camera on the usual tripod screw, and even more entirely
without a tripod. However, any visible errors that are caused by a shifted camera will require more
effort in postprocessing.
When you have no tripod, note that you must not rotate the camera on your outstretched arm!
Rather, the camera’s entrance pupil must be rotated, so you should appear to dance around the
5 In

many references you will find “Nodal Point” mentioned here. But see these: http://en.,

7.2 Creating Panorama Photographs for Stellarium


Figure 7.4: Automated panorama head. (Source: Wikipedia

The images should match in brightness and white balance. If you can shoot in RAW, do so to
be able to change white balance later. If the camera can only create JPG, ensure you have set the
camera to a suitable white balance before taking the photos and not to “auto”, because this may
find different settings and thus give colour mismatches. Exposure brightness differences can be
largely removed during stitching, but good, well-exposed original shots always give better results.
As a general recommendation, the images of a panorama should be taken from left to right,
else please accordingly invert some of the instructions given below.
There are several panorama making programs. Often they are included in the software that
comes with a digital camera and allow the creation of simple panoramas. Other software titles are
available for purchase. However, there is one cost-free open-source program that does everything
we need for our task, and much more:

Hugin Panorama Software
Hugin6 , named after one of the ravens that sits on Odin’s shoulder and tells him about the world,
is a user-friendly catch-all package with graphical user interface that allows creating panoramas
with a single application. Actually, Hugin is a GUI application which calls several specialized
sub-programs with fitting parameters. The instructions are based on Hugin V2014.0 and 2015.0.
Typically digital images come in JPG format with information about camera, lens, and settings
stored in invisible metadata in the EXIF format. When Hugin reads such images, it can automatically derive focal length, field of view, and exposure differences (exposure time, aperture, color
balance) to create panoramas as easily as possible.
After starting Hugin for the first time, select Interface Expert to release several options not
visible to “beginners”. In the Preferences dialog ( Files Preferences ), edit number of CPU to

Chapter 7. Landscapes


match the number of cores in your computer and allow parallel processing. E.g., if you have an
Intel Core-i7, you usually can set up to 8 cores (4 cores with hyperthreading; but maybe leave
one core for your other tasks while you wait for a processing job?). If your PC is equipped with a
modern programmable graphics card, you can enable its use in the Programs tab with activating
“Use GPU for remapping”.
After that, we are ready for creating our panoramas.

Regular creation of panoramas
The graphical user interface (GUI) consists of a main menu, symbols, and 4 tabs. We start on the
tab Photos.
• Add images. . . Opens a file browser. Select the images which you want to stitch. Usually,
lens data (focal length, field of view, . . . ) are read from the EXIF data. If those are not
available (e.g. cheap cameras, images scanned from film), you can enter those data on
loading or later. The images are now listed in the file list, and you can edit image parameters
by marking one or more, and then choosing from the context menu which you get from
pressing the right mouse button. In case you have used different lenses (or inadvertently
used different focal lengths of a zoom lens), you can assign separate lenses to the images.
Caveat: If you have resized the images, or produced copied on your RAW converter with
non-native resolution, the Field of View (FoV) in Hugin may be misidentified. You must
edit lens parameters and fill in the field of view from a full-size image. Else the first round
of optimisation will run into unsolvable trouble.
• Select one image as position anchor (usually the center image), and one as exposure anchor
(this can be the same image). For our purpose, the anchor image should face south.
• Next, we must find common feature points. The next field below provides the required
settings. It is recommended to use the CPFind command. To avoid finding control points
in (moving) clouds, select setting Hugin’s CPFind + Celeste 7 . Then press Create control points .
This opens a dialog box in which you can see output of the selected feature point extractor.
It should finish with a box telling you the number of identified points. In rare cases some
images cannot be linked to others, you will have to manually add or edit feature points in
those cases.
• Now it’s time to start optimisations. On the Geometric Optimimisation combo, start with
the button Positions, incremental from anchor , and press Calculate . Moments later, a first
rough match is available for inspection.
• First open the Preview window (press Ctrl + P or click the blue icon). Assumed your
images cover the full horizon, the window shows an equirectangular area (360 degrees along
the horizon and 180 degrees from zenith to nadir). The anchor image should be close to the
image center, and the other images should be already well-aligned to both sides. You can set
the exact center point by clicking it in the image. If the horizon appears badly warped, use
the right mouse key and click on the horizon roughly near −90 or +90 degrees (halfway to
the left or right).
• Open the OpenGL preview window (press Ctrl + Shift + P or click the blue icon with GL
inside). This panel provides several important views:
– The Preview tab is similar to the non-OpenGL preview. You can display an overlay of
the control points, which are colored according to match quality. Also, with button
Identify activated, you see the overlapping image frames when you move the mouse
over the image.
– The Layout tab helps finding links between images.
– The Move/Drag dialog may help to interactively adjust a panorama.
7 If

you forget this, you can remove cloud points by calling Celeste in the control point editor later

7.2 Creating Panorama Photographs for Stellarium


Sometimes the preview image may however be distorted and unusable.
• Open the Control Points Table dialog (press F3 or click the “table” button). Here you see
the points listed which link two images. Clicking a column label sorts by this column. It is
recommended that only neighboring overlapping images should be included here. If you
have very large overlap, it is possible that points are found between two images which are
not directly adjacent. In the OpenGL preview window, you can use the Preview or the
Layout tabs to identify those image pairs. Such points should be deleted. In the point table,
click on columns “Right Img.”, then “Left Img.”, and then find pairs like 0/2, 1/3, 2/4 etc.
Mark those lines, and delete the points.
• To re-run the optimisation, press the double-arrow icon or the calculate button in the
Optimise/Geometric area.
Preliminary Geometric Optimisation
Now the (usually) longest part begins: Iterative optimisation of the photo matchpoints. If your
images were taken on a panorama tripod head, there should only be very few bad matchpoints, e.g.
those found on persons or clouds8 which have moved between photos. For handheld photos, the
following considerations should be observed.
The most important line which we want to create in all perfection is the visible horizon, where
sky and earth meet. The foreground, usually grassy or rocky, is of lesser interest, and stitching
errors in those areas may not even be relevant.
Therefore, matchpoints with large errors in the foreground can be safely removed, while, if
necessary, points on the horizon should be added manually. Use the Control Points tab, select
adjacent images (start with 0 on the left and 1 on the right side), and delete the worst-fitting
matchpoints closest to the camera (near the bottom of the images). We now start a long phase of
re-optimizing and deletion of ill-matching points as long as those are far from the horizon. When
all near matchpoints are deleted, the result should already look not too bad.
For continued optimisation, the number of parameters to optimize can be extended. To begin, I
recommend Positions and View (y, p, r, v) , which may find a new focal length slightly different from
the data in the EXIF tags. Again, delete further foreground points. If after a few rounds you
still have bad point distances, try Positions and Barrel Distortion (y, p, r, b) to balance distortion by bad
optics, or even go up to Everything without translation . Optimisation can only reach perfect results if
you did not move between exposures. Else, find a solution which shows the least error.
In case you took your photos not on a tripod and moved too much, you may even want to play
with the translation options, but errors will be increasingly hard to avoid.
Using Straight Edges as Guides
If the panorama contains straight lines like vertical edges of buildings, these can be used to
automatically get a correctly levelled horizon: Vertical lines are mapped to vertical lines in
equirectangular panos! In the Control Points tab, select the image with the vertical edge in both
subframes, and mark points on the vertical edge. (switch off auto-estimate!). Likewise, horizontal
lines may help, but make sure lines like rooves are perpendicular to your line of view, else the
perspective effect causes an inclination.
Multi-ring Panoramas
If you are trying to create a panorama with several rings (horizon, one or two rings below, and
nadir area), you must try to create/keep control points that best give a result without visible seams.
In this case, and esp. if you have only used a regular tripod or even dared to go for a free-handed
panorama, you may observe that it is best to remove control points in neighboring photos in the
8 You

should have created control points with the Celeste option!


Chapter 7. Landscapes

lower rings, but keep only the “vertical” links between images with similar azimuth.
In total, and if the foreground is not important but only grassy or sandy, the rule of thumb is
that the horizon images must be strongly linked with good quality (small errors), while images in
the lower rings should be linked mostly to their respective upper photos, but not necessarily to the
images to its sides. The resulting panorama will then show a good horizon line, while stitching
artifacts in a grassy or otherwise only decorative ground will usually be acceptable and can, if
needed, be camouflaged in postprocessing.
This optimisation and editing of control points is likely a longish iterative process, and these
are the late night hours where you will finally wish you had used a panorama head. . .
If you have images with overlapping areas, you can usually not force Hugin to take pixels from the
image which you find best. you can however mask off an area from an image which you don’t want
to see in the output under any circumstances, e.g. a person’s arm or foot in one image. Just open
the image in the Mask tab and either press Add new mask and draw the mask polygon covering
the unwanted area, or use the crop settings to define rectangular areas to use.
Exposure disbalance
In the Photos tab, select Photometric parameters on the right side. The EV column lists the
Exposure Value. If you see disbalance here and in the preview window, you can run a photometric
optimisation with the lowest button on the Photos tab. Simply select Low dynamic range and press
Calculate . The preview should now show a seamless image. If all else fails, you can edit the EV
values directly.
Advanced photographers may want to correct exposures in their RAW images before creating
JPG or TIF images to combine with Hugin. This unfortunately may create exposure disbalance
because the EXIF tags may not be adjusted accordingly, so based on different exposure/f-stop
conbinations Hugin may think it has to re-balance the values. In these cases, don’t run the
photometric optimiser. Some image exposure values have to be changed manually, and the effect
supervised in the preview window. Usually the smooth blending in the subprogam enblend called
by Hugin will hide remaining differences.
When you are happy with the panorama in the preview window and the matchpoints promise a good
fit, it is time to finally create the panorama image. Hugin can create a large number of different
projections which all have their application. For Stellarium, we can only use the equirectangular
projection. You still have 2 options:
spherical landscapes (see 7.1.3) require single equirectangular images, the maximum size depends
on your graphics hardware and Qt limitations and is likely not larger than 8192 × 4096
old_style landscapes (see 7.1.4) can use several textures for the ring along the horizon, and one
image for the nadir zone. If you need high resolution, you should aim for creating this one.
Sometimes, creating the nadir zone is difficult: this is where usually the view is blocked by the
tripod, and we are not interested in views of tripod or our own feet. For our purpose it is usually
enough to fill in the feet area using the clone stamp, or a monochrome color, or, for old_style
landscapes, you can instead insert an oriented site map or wind rose.
There is a button create optimal size in Hugin. It may recommend a panorama width around
13.000 pixels for an average camera and photos taken with a wide-angle lens. Increasing this size
will most likely not lead to higher optical resolution! The panorama width which you can most
usefully create depends on the resolution of the source images (which leads to the result given by
Hugin) and on your needs. If you need arcminute resolution, you would aim for 360 × 60 = 21600

7.3 Panorama Postprocessing


pixels, which cannot be loaded into graphics memory in a single piece, i.e., is too large for
Stellarium, and must be configured as old_style landscape. In this case, 10 or 11 tiles of
2048 × 2048 pixels (totalling 20480 or 22528 pixels) is the closest meaningful setting, i.e., you
could create an image of 20480 pixels width and cut this into usable pieces. Usually, a size
of 4096 × 2048 or 8192 × 4096 pixels (for better computers) is enough, and can be used in a
spherical landscape.
We have to edit the file after stitching, therefore select creation of an image in the TIFF format.
LZW compression is non-lossy, so use this to keep file size reasonably small.
For regular images, it is enough to create “Exposure corrected, low dynamic range”. If you
have a problem with persons that have moved between your images, you may want to post-process
the final result with import of the distorted sub-images and manually defining the best blending line.
For this, find the “Remapped Images” group and again activate “Exposure corrected, low dynamic
Now, press the Stitch! button in the lower right corner. This opens a helper program which
supervises the stitching process. Depending on your computer and size of the image, it will require
a few minutes of processing.
In case stitching fails with a cryptic error message, try to add the option --fine-mask to the
enblend options.
Store a copy of the Hugin project file to always be able to go back to the settings you used to
create the last panorama. We will get back to it when we want to make a truly calibrated panorama
(see 7.3.3).


Panorama Postprocessing
The image created has to be further processed to be used in Stellarium. The most obvious change is
the need for a transparent sky, which we can easily create in programs like Adobe Photoshop or
the free and open-source GIMP. I will describe only the free and open-source solution.
After that, we have to bring the image into shape for Stellarium, which may include some
trimming. While we could also slice an image with interactive tools, higher accuracy and repeatable
results can be achieved with command-line programs, which makes the ImageMagick suite the
tool of our choice.


The GIMP (GNU Image Manipulation Program) has been developed as free alternative to the
leading commercial product, Adobe Photoshop. While it may look a bit different, basic concepts
are similar. Not everybody can (or wants to) afford Photoshop, therefore let’s use the GIMP.
Like Photoshop, the GIMP is a layer-aware image editor. To understand the concept, it is
easiest to imagine you operate on a growing stack of overhead slides. You can put a new transparent
slide (“layer”) on top of the stack and paint on this without modifying the lower layers.
A few important commands:
Zooming Ctrl + Mouse Wheel
Layer visibility and transparency Make sure to have layer dialog shown ( Windows Dockable Dialogs ).
A gray bar indicates opacity for the currently active layer. Note the mouse cursor in this
opacity bar (often also called transparency bar): near the top of the bar the upward pointer
immediately sets percentage. A bit lower the pointer looks different and can be used for
The most obvious postprocessing need for our panorama is making the sky transparent. The
optimal tool usually is the “Fuzzy Select”, which is equivalent to the “Magic Wand” tool in

Chapter 7. Landscapes


Photoshop. Simply mark the sky, and then delete it. The checkerboard background indicates

transparent pixels.
It sometimes helps to put an intensive bright red or blue background layer under the panorama
photo to see the last remaining clouds and other specks. In the layer dialog, create a new layer,
bucket-fill with blue or red, and drag it in the layer dialog below the pano layer. Write-protect this
layer, work on the image layer, and before exporting the image layer with transparent sky to PNG,
don’t forget to switch off the background.
We need this layer functionality especially to align the panorama on a calibration grid, see
section 7.3.3.

ImageMagick (IM)9 can be described as “Swiss Army Knife of image manipulation”. It can do
most operations usually applied to images in a GUI program, but is called from the command line.
This allows also to include IM in your own command scripts10 . We will use it to do our final cut
and resize operations. I cannot give an exhaustive tutorial about more than a few of IM’s functions,
but the commands given here should be enough for our purpose.
To open a command window (console, a.k.a. DOS window), press the Windows key and enter
cmd, then press
. (On Linux and Mac, you surely know how to open a console window.)
There are some things you might need to know:
• The command line is not your enemy, but a way to call expert tools.
• The Windows command line processor cmd.exe is far from user friendly.
• There are remedies and alternatives. See notes on clink (7.4.3) for a considerable improvement, and Cygwin (7.4.4) for experts.
Command-line magick for spherical landscapes
Let’s start with the commands for final dressing of an equirectangular panorama to be used as
spherical landscape which has been created in size 4096 × 2048, but where you have seen that
nothing interesting is in the image above 11.25◦ . This means we can cut away the sky area and
compress the image to 4096 × 1024 to save graphics memory.11
To understand the numbers in the example, consider that in a panorama image of 4096 × 2048
pixels, 1024 pixels represent 90◦ , 512px = 45◦ , 256px = 22.5◦ , 128px = 11.25◦ . To keep a top
line of 11.25◦ , we keep an image height of 1024 + 128 = 1152px, but the crop starts at pixel
Y = 1024 − 128 = 896.
convert landscape . png - crop 4096 x1152 +0+896
- resize 4096 x1024 ! landscape_cropped . png
Note the exclamation mark in the -resize argument, which is required to stretch the image in a
non-proportional way.
Alternatively, you can operate with IM’s “gravity”, which indicates the corner or edge geometric
offsets are referred to. Given that we want the lower part of the image to exist completely, you only
need to compute the size of the cropped image:
convert landscape . png - gravity SouthWest - crop 4096 x1152 +0+0
- resize 4096 x1024 ! landscape_cropped . png
You still need the addition +0+0 in the -crop option, else the image will be cut into several pieces.
In the file landscape.ini, you then have to set maptex_top=11.25.
10 These

may typically be .BAT files on Windows, or various shell scripts on Linux or Mac.
modern graphics cards no longer require the “powers of two” image sizes, but we keep this practice
to increase compatibility.
11 Most

7.3 Panorama Postprocessing


Command-line magick for old_style landscapes
Let us assume we want to create a high-resolution landscape from a pano image of width 16384
which we have carefully aligned and calibrated on an oversized grid template that also shows a
measured horizon line (see 7.3.3). Usually it is not necessary to create the full-size image, but only
the horizon range, in this high resolution. Assume this image has been aligned and justified on
our grid image and is HEIGHT pixels high, the left border is at pixel X_LEFT, and top border (i.e.,
the point where relevant content like the highest tree is visible) is on pixel Y_TOP. Assume our
graphics card is a bit oldish or you aim for maximum compatibility, so we can load only textures of
at most 2048 pixels in size. Given that the horizon area usually only covers a few degrees, a vertical
extent of 2048px seem a pretty good range for that most interesting zone. The ground can then be
filled with some low-resolution image of grass, soil, or a properly oriented site map, or you can use
Hugin to create a ground image (and using the maximum of 2048 × 2048 also here usually is far
more than enough).
In GIMP (or Photoshop, . . . ), we must find the values for X_LEFT, Y_TOP and HEIGHT. HEIGHT
is being resized to 2048, strictly, by the exclamation mark in the resize command. We can create
our image tiles now with this singular beast of a command line (write all in 1 line!), which puts our
convert PANO . png - crop 16384 xHEIGHT + X_LEFT + Y_TOP + repage
- resize 16384 x2048 !
- type TrueColorMatte - depth 8
- crop 2048 x2048 + repage
This creates 8 images. See section 7.1.4 for the landscape.ini where these images can be
referenced. Don’t forget to read off top and bottom lines (altitudes in degrees) from your grid,
the vertical extent will form the decor_alt_angle, and the bottom line the decor_angle_shift
entries in this file.
Creating a ground image for old_style landscapes
When you want a good ground image for an old_style landscape from your panorama and not
just fill the groundtex with a monochrome texture or a map, you have to create a ground view in
Hugin. But you may have already created a huge pano! This can also be used as source image, and
a ground shot can be extracted with a reversed operation. In principle, all you need to know is the
field of view around the nadir. Figure 7.5 shows a simple configuration file.
# hugin project file
# hugin_ptoversion 2
p f0 w2048 h2048 v92 E0 R0 n " TIFF_m ␣ c : LZW ␣ r : CROP "
m g1 i0 f0 m2 p0 .00784314
# image lines
# - hugin cropFactor =1
i w16384 h8192 f4 v360 Ra0 Rb0 Rc0 Rd0 Re0 Eev0 Er1 Eb1 r0
p90 y0 TrX0 TrY0 TrZ0 Tpy0 Tpp0 j0 a0 b0 c0 d0 e0 g0 t0
Va1 Vb0 Vc0 Vd0 Vx0 Vy0 Vm5 n " Eqirect_Pano360 . png "

Figure 7.5: Project file ground.pto usable to create the ground image with Hugin or, on
the command line, its nona stitcher. The last line, starting with i, has been wrapped, but
must be 1 line.

Chapter 7. Landscapes


Say, the side panels extend down to decor_angle_shift=-44 degrees, which means you
must close the ground with a Nadir FoV = 2 × (90 − 44) = 92. For maximum compatibility, we
will again make an image of width and height both 2048px. These values can be found in the p line
in Figure 7.5. The i line describes the input image, which is our full equirectangular pano of width
w= 16384 and height h= 8192. The last argument of that line is the image file name.
For processing, we do not use the Hugin GUI, but simply the command line. The actual
program to call is nona. If your stitched panorama is a 16-bit TIFF, nona will also make a 16-bit
image, but our textures are limited to 8-bit PNGs. We apply our most useful tool, convert from the
ImageMagick suite.
nona -v -m PNG ground . pto -o ground . png
convert ground . png - depth 8 ground_8bit . png
The file ground_8bit.png is then used in the groundtex field on landscape.ini.

Final Calibration
The creation of a calibrated panorama (which can be regarded as dependable proxy for further
measurements taken inside Stellarium) requires reference measurements to match the photos against.
We must take azimuth/altitude measurements with a theodolite or total station, in the optimal case
along the full horizon, and in addition I recommend to take azimuth and altitudes of some distinct
features along the horizon which must also be visible in the photographs: mountain summits,
electrical towers, church towers, . . .
I recommend you create grid templates of the sizes you are going to create, e.g. 4096, 8192,
16386 and 20480 pixels wide with some diagram tool. On these, you can then also draw the
measured horizon line.
Now, load a panorama on top of this in the GIMP, i.e., copy it into a separate layer over the
grid image, and set it semi-transparent.
Try to align the center of the image (where the geometric anchor has been defined; remember:
this should be the image pointing south!) with the measured horizon line or the distinct features.
The optimal solution consists of a photo panorama which aligns perfectly with the measured
line and features. We now have to iteratively bring deviations to a minimum. The process depends
on processor speed, image size, your training and – most of all – your requirements in accuracy!
In the GIMP, load your grid image with horizon line. Now select File Open as Layers. . . ,
load your photo panorama, and then set layer transparency in the Layers dialog to about 50%.
Select the double-arrow tool to move the panorama via mouse drag and cursor keys over the
grid, and align the outline of the photo horizon’s southern point with the measured line. Now it’s
time to estimate the quality of the panorama.
In Hugin’s Photos tab, select the Positions view on the right side. Now you see “Yaw”, “Pitch”
and “Roll” values of camera-to-world orientation listed in the photos list. It should now be possible,
by changing the values only for the anchor image and re-optimizing, to come to a panorama with
only minimal error. In the process, start with Optimising Positions incremental from anchor ,
then go for view and barrel optimisation, and so on. Always try to remove foreground match points
which have large error and are irrelevant for the task to match the horizon. Those are especially
cross-matches of horizon and subhorizon rows of images. Only vertically and horizontally adjacent
images should be required to match. For handheld panoramas, also links between adjacent images
in the non-horizontal rows are usually too erroneous to be useful, just remove these match points.
Use the Layout tab in the Fast Panorama Preview to see the relations between images (Fig. 7.6):
Red lines have big errors, green lines are good, thin gray lines indicate possible overlap without
specified match points. After each optimisation step, export a new pano image, load as layer in
GIMP, and check again.

7.3 Panorama Postprocessing


Figure 7.6: Hugin’s Fast Panorama Preview can be used to check which images are
connected to its neighbours. Most important are good matches along the horizon, the
images in the lower rows are clearly less important. If captured on a tripod, they should
still match.

Basic rules to observe (use obvious inverses).
• If image aligns well in azimuth but overshoots the grid to the right: Increase yaw accordingly (0.022◦ /pixel if image is 16384 pixels wide).
• If the north end (left and right borders) is higher than the southern contact point: Increase
pitch angle.
• If north and south points are OK, but the western (right) half is higher than the eastern
(left) half: Increase Roll angle.
The corrections required for pitch and roll may be surprisingly small!
Within a few rounds of adjustments, panorama creation, adding as layer in the image editor,
and comparing to the reference data, you should achieve a match to fit your needs.
In case you have taken photographs in several rings but without a panorama tripod, you
may have to first align only the horizontal images (deselect the lower images to exclude from
optimisation), and when the horizon ring is aligned perfectly, deactivate further optimisation in
Hugin for those photos while “attaching” (optimising) the lower photos. In Hugin’s Photos tab,
select Optimise Geometric Custom Parameters . This opens an extra tab Optimiser , where
you can fine-tune your needs: Switch off all variables for the photos in the horizon ring, and make
sure the lower photos fit in the preview after optimisation.
It may even help to define that the lower rows have been taken with a different Lens, so the
field of view and distortion settings of the horizon row will be used as it had been found during the
horizon-only match.
By now you should have enough experience what level of error may be acceptable for you.

Chapter 7. Landscapes


Artificial Panoramas
I have created a website12 where you can enter geographical coordinates and download a file
pano.kml which helps with image creation from Google Earth imagery. Store this file for a site,
let us call it MYPLACE , into a new directory GE_MYPLACE inside your landscapes directory.
Store all scenes visible from the respective viewpoint MYPLACE as picture into one common
folder in your landscapes/GE_MYPLACE under the viewpoint name, e.g., 75-30.jpg, which
means 75 degrees from Nadir, azimuth 30 degrees. Also, double-click the pano entry or the marker
in Google Earth to open a window with the basic content of your landscape.ini. Copy and
paste from there into a new file landscape.ini and adjust the obvious entries. Complete as
required with the entries described in section 7.1.3.
On loading of the images, Hugin will not be able to detect any EXIF lens data and ask you
for the horizontal field of view. Enter 60 degrees, which is the standard value for Google Earth
screenshots13 .
The viewpoint names translate almost directly to the yaw and pitch angles which you can enter
in the image list in Hugin’s Photos tab. For example, switch to the Positions display on the right
window edge in the Photo tab, mark all images that start with 25- and assign a pitch angle of
−90 + 25 = −65. The second part of the names is directly the azimuth. In this case, don’t run
the optimizer, but you can immediately set an output resolution and stitch (see 7.2.3). To get rid
of the image decorations (compass etc), apply masks14 . Postprocessing steps are the same as for
photo-panoramas: make sky invisible, crop, etc.
It is also interesting to switch on the 3D buildings layer before creating the images. If temples
or other buildings are accurate, this will give an even closer approximation to what would be visible
on-site. Note however that not every building will be modelled in usable quality, and that usually
vegetation is not included in the 3D buildings layer. Also, if you are too close to buildings, they
may be cut away by the near clipping plane of the rendering.
These images, based on Google Earth imagery and the SRTM topographic model, seem usable
as first rough approximation to a photo-based or surveyed panorama. Note that it is definitely not
accurate enough for representing nearby horizon features or critically important mountain peaks,
and please note that Google has image copyright which at least requires you to acknowledge when
displaying these pictures.


Nightscape Layer
Since version 0.13, Stellarium can simulate artificial illumination, like streetlamps, bright windows,
or the skyglow over cities (Zotti and Wuchterl, 2016). One way to create this layer is to make 2
panorama series during the day and night and process these in the same Hugin project to align
those photos, and then stitch two separate images by selecting either the daylight or the nighttime
shots. The night panorama has to be processed to remove stars, airplanes, etc.
The other way is a simple layer overpainted in the image processing program. As rough
recommendation, use several layers to prepare this feature:
• Put a semitransparent black layer over your daylight image, this helps you to place your
painted pixels.
• Paint windows, street lamps, signs, . . . . You may apply a layer style to produce some glow.
• To draw an impression of more light in the atmosphere (city skyglow), use a gradient with
some brownish color. Generally the color depends on the appropriate mix of city lights
(sodium, mercury vapour, etc.). Note that on the city outskirts a simple vertical gradient will
13 Note

that if you work with Google Earth Pro, you can create different FoV!
is a wide overlap in the images to allow generous trimming.

14 There

7.4 Other recommended software


not work, towards the city the horizon is much brighter. Use a huge but weak brush to make
a more spotty sky.
• Use the existing landscape as template for the layer mask for this gradient sky layer. (You
want to hide skyglow by leaves in the foreground!)
• If you want to add only a few lights to an old_style landscape, you need to provide only
the panels showing those lights. Just load a side panel for reference, place a new layer on top,
and paint the lights on windows, lamps etc. There is no light option for the ground texture.
This makes old_style landscapes best suited for localized light pollution, not city skyglow.
The resulting image is then declared in the maptex_illum line of landscape.ini. Try also
to balance the global strength of light pollution with the light_pollution key, and a probable
minimal brightness with the minimal_brightness key.
Try to match the visual appearance, not necessarily what photographs may have recorded.
E.g., the Grossmugl sky shows horizon glow mostly towards the city of Vienna, where long-time
exposures may already be saturated.
The possibilities seem limited only by your time and skills!


Other recommended software
Here is a short collection of other useful programs for (panorama) image manipulation and other
tasks on Windows.


IrfanView is a free image viewer for Windows with many options. It can show almost any image
format, including several camera RAW formats, in windowed and full-screen mode. It is definitely
preferrable over any image viewer built into Windows. Unfortunately however, it has no panorama
viewer function!


FSPViewer15 by Fulvio Senore is an excellent panorama viewer for equirectanglar images. Images

centered along the horizon can be viewed directly, while settings for images with different minimum
and maximum angles, as well as “hotspots” (similar to hyperlinks) which move to neighboring
panoramas, can be configured in an .FSV text file like figure 7.7.
ImageName = Horizon_Rosenburg . jpg
WindowTitle = Horizon_Rosenburg
hFov =70
# Formula : HP =100*( h /2 - upper )/( lower - upper ) in Hugin crop , or
HP =100* zeroRow / imgHeight
HorizonPosition =33.8

Figure 7.7: FSP configuration file (example)

Clink16 is a command line enhancement for Windows developed by Martin Ridgers. If you have
ever worked under a Linux bash-like command line, you will easily feel that Windows’ cmd.exe
15 Further

details are available on its home page



Chapter 7. Landscapes

is extremely limited. Clink provides several useful features, most notably a really usable commandline completion. It is not essential for our tasks, but a general improvement of usability of the
Windows command line which else has not caused me any trouble.

Compared to Linux, the command line of Windows can be a humbling experience. None of the
wonderful helpers taken for granted on Linux are available. Cygwin17 provides a command line
console with bash shell and all the niceties like make, awk, sed, etc. which seem essential for
routine work. If you are used to Linux tools, use inline scripts in your Makefiles and need more
than Clink can offer, you should install Cygwin.


Alternative to Cygwin, several of those nice tools (sed, awk etc.) have also been made available as
standalone commands for Windows. If you don’t need the inline scripting capabilities in Makefiles
which you would get from Cygwin but just want to call awk or sed inside your .BAT scripts, maybe
this is enough.


8. Deep-Sky Objects

Since version 0.10.0 Stellarium uses the “json” cataloguing system of configuring textures. At
the same time the Simbad online catalogue was added to the search feature, making the catalog
somewhat redundant and used now only as a first search point or if there is no internet connection.
If the object has a name (not just a catalogue number), you should add one or more records to
the .../nebulae/default/names.dat file (where ... is either the installation directory or the
user directory). See section 8.1.2 Modifying names.dat for details of the file format.
If you wish to associate a texture (image) with the object, you must add a record to the
.../nebulae/default/textures.json file. See section 8.1.3 for details of the file format.
If you wish to associate an outline with the object, you must add the series of lines to the
.../nebulae/default/outlines.dat file. See section 8.1.4 for details of the file format.


Stellarium DSO Catalog
Stellarium’s DSO Catalog contains over 90000 objects1 (up to 15.5m for galaxies) and is available
for end users as collection of files:
catalog.txt Stellarium DSO Catalog in ASCII format for editing data
catalog.dat Stellarium DSO Catalog in zipped binary format for usage within Stellarium
List of proper names of the objects from file catalog.dat
ASCII file can be converted into binary format through enabling an option in the file config.ini
(See 5.4):
[ devel ]
convert_dso_catalog = true
The file catalog.txt should be put into the directory .../nebulae/default/ and you
should create an empty file catalog.pack to storing the binary catalog. After converting the data
into binary format you should gzip them by the command
1 An

extended edition of this catalog with over one million objects may be downloaded and installed
manually (see section 5.5.2).

Chapter 8. Deep-Sky Objects

gzip - nc catalog . pack > catalog . dat



Stellarium DSO Catalog contains data and supports the designations for follow catalogues:
NGC New General Catalogue
IC Index Catalogue
M Messier Catalog
C Caldwell Catalogue
B Barnard Catalogue (Barnard, 1927)
SH2 Sharpless Catalogue (Sharpless, 1959)
VdB Van den Bergh Catalogue of reflection nebulae (van den Bergh, 1966)
RCW A catalogue of Hα-emission regions in the southern Milky Way (Rodgers, Campbell,
and Whiteoak, 1960)
LDN Lynds’ Catalogue of Dark Nebulae (Lynds, 1962)
LBN Lynds’ Catalogue of Bright Nebulae (Lynds, 1965)
Cr Collinder Catalogue (Collinder, 1931)
Mel Melotte Catalogue of Deep Sky Objects (Melotte, 1915)
PGC HYPERLEDA. I. Catalog of galaxies2
UGC The Uppsala General Catalogue of Galaxies
Ced Cederblad Catalog of bright diffuse Galactic nebulae (Cederblad, 1946)
Arp Atlas of peculiar galaxies (Arp, 1966)
VV The catalogue of interacting galaxies by Vorontsov-Velyaminov (Vorontsov-Velyaminov,
Noskova, and Arkhipova, 2001)
PK Version 2000 of the Catalogue of Galactic Planetary Nebulae (Kohoutek, 2001)
PN G The Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker et al., 1992)
SNR G A catalogue of Galactic supernova remnants (Green, 2014)
ACO A Catalog of Rich Clusters of Galaxies (Abell, Corwin, and Olowin, 1989)
Cross-index data for Stellarium’s DSO Catalog is partially obtained from “Merged catalogue of
reflection nebulae” (Magakian, 2003) and astronomical databases SIMBAD3 (Wenger et al., 2000)
and NED4 .
Modifying catalog.dat
This section describes the inner structure of the files catalog.dat (binary format) and catalog.txt
(ASCII format). Stellarium can convert ASCII file into the binary format file for faster usage within
the program.
Each line contains one record, each record consisting of the following fields with tab char as
2 The




Deep-Sky Object Identificator
RA (decimal degrees)
Dec (decimal degrees)
B magnitude
V magnitude
Object type (See section 8.1.1 for details).
Morphological type of object
Major axis size or radius (arcmin)

PGC and UGC catalogues are partially supported
Astronomical Database —
4 NASA/IPAC Extragalactic Database (NED) —

8.1 Stellarium DSO Catalog







Minor axis size (arcmin)
Orientation angle (degrees)
Error of redshift
Parallax (mas)
Error of parallax (mas)
Non-redshift distance ( Mpc for galaxies, kpc for other objects)
Error of non-redsift distance ( Mpc for galaxies, kpc for other objects)
NGC number (New General Catalogue)
IC number (Index Catalogue)
M number (Messier Catalog)
C number (Caldwell Catalogue)
B number (Barnard Catalogue)
SH2 number (Sharpless Catalogue)
VdB number (van den Bergh Catalogue of reflection nebulae)
RCW number (A catalogue of Hα-emission regions in the southern
Milky Way)
LDN number (Lynds’ Catalogue of Dark Nebulae)
LBN number (Lynds’ Catalogue of Bright Nebulae)
Cr number (Collinder Catalogue)
Mel number (Melotte Catalogue of Deep Sky Objects)
PGC number (HYPERLEDA. I. Catalog of galaxies); partial
UGC number (The Uppsala General Catalogue of Galaxies); partial
Ced identificator (Cederblad Catalog of bright diffuse Galactic nebulae)
Arp number (Atlas of Peculiar Galaxies)
VV number (The catalogue of interacting galaxies)
PK identificator (Catalogue of Galactic Planetary Nebulae)
PN G identificator (The Strasbourg-ESO Catalogue of Galactic Planetary
SNR G identificator (A catalogue of Galactic supernova remnants)
ACO identificator (A Catalog of Rich Clusters of Galaxies)

Types of Objects
Possible values for type of objects in the file catalog.dat.



Active Galaxy
Radio Galaxy
Interacting Galaxy
Globular Cluster
Open Cluster
Planetary Nebula
Dark Nebula
Reflection Nebula
Cluster associated with nebulosity
HII Region

Chapter 8. Deep-Sky Objects


Supernova Remnant
Supernova Candidate
Supernova Remnant Candidate
Bipolar Nebula
Emission Nebula
Stellar Association
Star Cloud
Infra-Red Object
Possible Quasar
Interstellar Matter
Emission Object
LINEAR-type Active Galaxies
BL Lac Object
Molecular Cloud
Young Stellar Object
Possible Planetary Nebula
Protoplanetary Nebula
Double Star
Multiple Star
Symbiotic Star
Emission-line Star
Cluster of galaxies
Unknown type, catalog errors, Unidentified Southern Objects etc.

Modifying names.dat
Each line in the file names.dat contains one record. A record relates an extended object catalogue
number (from catalog.dat) with a name. A single catalogue number may have more than one
record in this file.
The record structure is as follows:
Offset Length Type Description
5 %5s Designator for catalogue (prefix)
15 %d
Identificator for object in the catalog
60 %s
Proper name of the object (translatable)
If an object has more than one record in the file names.dat, the last record in the file will be used
for the nebula label.


Modifying textures.json
This file is used to describe each nebula image. The file structure follows the JSON format, a
detailed description of which may be found at The textures.json file which
ships with Stellarium has the following structure:
serverCredits (optional) a structure containing the following key/value pairs:
short a short identifier of a server where the json file is found, e.g. “ESO”
full a longer description of a server, e.g. “ESO Online Digitised Sky Survey Server”
infoURL a URL pointing at a page with information about the server

8.1 Stellarium DSO Catalog


imageCredits a structure containing the same parts as a serverCredits structure but referring to
the image data itself
shortName an identifier for the set of images, to be used inside Stellarium
minResolution minimum resolution, applies to all images in the set, unless otherwise specified at
the image level
maxBrightness the maximum brightness of an image, applies to all images in the set, unless
otherwise specified at the image level
subTiles a list of structures describing indiviual image tiles, or referring to another json file. Each
subTile may contain:
shortName (name for the whole set of images, e.g. “Nebulae”)
miniResolution (applies to all images in set)
alphaBlend (applies to all images in set)
subTiles list of images. Each image record has the following properties:
imageCredits (itself a list of key/pairs)
imageUrl (e.g. file name)
worldCoords (a list of four pairs of coordinates representing the corners of the image)
textureCoords (a list of four pairs of corner descriptions. i.e. which is top left of image
minResolution (over-rides file-level setting)
Items enclosed in Quotation marks are strings for use in the program. Syntax is extremely
important. Look at the file with a text editor to see the format. Items in <> are user provided strings
and values to suit the texture and source.
" imageCredits "

: { " short " : " < author ␣ name > " ,
" infoUrl " : " http :// < mysite . org > "
" imageUrl "
: " < myPhoto . png > " ,
" worldCoords "
: [[[ X0 , Y0 ] , [ X1 , Y1 ] , [ X2 , Y2 ] , [ X3 , Y3 ] ]] ,
" textureCoords " : [[[ 0 ,0] ,[1 ,0] ,[1 ,1] ,[0 ,1]]] ,
" MinResolution " : 0.2148810463 ,
" maxBrightness " : < mag >

worldCoords Decimal numerical values of the J2000 coordinates (RA and dec both in degrees) of
the corners of the texture. These values are usually given to 4 decimal places.
textureCoords Where 0,0 is South Left, 1,0 the South Right, 1,1 North Right, 0,1 North Left
corners of the texture.
MinResolution UNDOCUMENTED VALUE! Sorry!
maxBrightness total object brightness, magnitude
Calculating of the coords of the corners of the images (plate solving) is a time consuming
project and needs to be fine tuned from the screen display. As most images will be two dimensional,
display on a spherical display will limit the size to about 1 degree before distortion becomes evident.
Larger images should be sectioned into a mosaic of smaller textures for a more accurate display.

Chapter 8. Deep-Sky Objects


Modifying outlines.dat
Each line in the file outlines.dat contains three “columns” of data for outline elements. The
structure for each line is as follows:
Offset Length Type Description
8 %d
Right ascension (decimal hours)
18 %d
Declination (decimal degrees)
60 %s
Coordinates for each point of outline is represented in the equatorial coordinate system for epoch
J2000.0. The possible values of the third “column” (Command) are:
start This command marks a start point of the outline. This command should also contain the
designation of the deep-sky object.
vertex This command marks an intermediate point of the outline.
end This command marks an end point of the outline.
Example for outline of M42:


start M 42

The format of the file outlines.dat is compatible with the similar file of the SkyChart/Cartes du Ciel planetarium.


Adding Extra Nebulae Images


Preparing a photo for inclusion to the textures.json file
The first step is to take a photo of the object you wish to display in Stellarium. When you have
the picture you will need to align it with the equatorial coordinate system so that north is directly
up and not inverted side to side or up and down as can happen with photos taken with a diagonal
mirror in the path. Next you will need to crop the picture, setting the main feature at the centre
and making the cropped size a factor of 2n eg. 64, 128, 256, 512, 1024 or 2048 pixels square
(or elongated like 512x1024). If this requirement is not met, your textures may not be visible, or
graphics performance may be seriously impacted. Textures larger than 2048 may only be supported
on high-end hardware. Images must be in PNG format. When cropping, make sure you leave at
least six prominent background stars.

8.2 Adding Extra Nebulae Images


Figure 8.1: Screen shot of nebula images displayed in Stellarium

Figure 8.2: Stellarium Textures Generator: A program to convert Equatorial coordinates
into decimal form and write a textures.json insert
The next step is to process your photo to make the background black, really black. This will
ensure that your background will meld with the Stellarium background and not be noticed as gray
square. Suitable programs to do all this are The GIMP5 or Photoshop if you can afford it.
When you have your image prepared you will need to plate solve it using at least 6 known GSC
stars that can be identified. That is why the cropping with plenty of stars was necessary. When
the plate is solved you will need to find the J2000 coordinates of the corners and convert them to
decimal values to form the world coordinates in the textures.json file.
The program Stellarium Textures Generator by Peter Vasey (Fig. 8.2) can convert the corner
coordinates of a texture found in your plate solving program into decimal values and write an insert
5 free

in keeping with the Stellarium spirit; available from

Chapter 8. Deep-Sky Objects


Figure 8.3: ReadDSS: A program to write a textures.json insert with epoch manipulation.
for the textures.json file.6
There is another program, ReadDSS (Fig. 8.3), written by Barry Gerdes in Qb64(gl), that will
perform the same task but allows manipulation of the epochs.7

Plate Solving
Suitable programs that can accept your picture and calculate its corner coordinates are hard to
find. I have only found one that suits our purpose and it is another expensive planetarium program,
TheSky X Pro. However the older versions TheSky 5 and 6 Pro will also do the job if suitably
configured, although I could not solve the test program with TheSky 6 that uses the same procedure
as TheSky 5.
These programs have a link feature that can match your photo to the selected area of the screen
and superimpose it on the display with a box around your photo provided it can match at least 6
stars from the GSC that is included with the program. When this is fitted you can read the corner
coordinates of your texture in the Status bar by selecting them with a mouse. TheSky X can read
these coordinates in J2000 values and uses textures in the FITS format, but the earlier programs
only read the coordinates of the current program date. To read the J2000 coordinates it is necessary
to re-start the program with the date set to 1-1-2000.
To add the picture to TheSky 5 you need first make a mono 8 bit version of the photo and place
it on the clipboard. Run TheSky and centre on the object centre. Look in the Tools menu for the
image link and select setup . Tick show image frame to put a frame around the image.
Paste the clipboard image on the display and use the zoom and position controls to get it as
close to the size and position as possible by visually matching stars. Go to the menu again and click
on link wizard . If you have been successful the window will show the number of stars matched
and the option to accept or continue . Accept and you will now see all the matched stars have
overlaid the picture. You can now read off the corner coordinates from the status bar starting at the
bottom (south) left and continuing counterclockwise to the top (north) left.


Processing into a textures.json insert
Place your image in the *.png format in the .../nebulae/default/ folder. Ensure that the name
matches the textures.json entry.
Once you have the corner coordinates of your photo you can add them to the decimal converter
program and it will write an insert nebula.json as a text file that you can paste directly into the
6 It

is available as a freebee from

8.2 Adding Extra Nebulae Images


textures.json file that is in the .../nebulae/default/ folder.
Save the textures.json file with the new insert and run Stellarium. Find the object in the
F3 Object selection window and slew to it. Your image should be there and with a bit of luck
it will nicely overlay the stars in Stellarium. However this only rarely happens, so a little bit of
tweaking of the JSON worldcoords will be needed to get a perfect match. Select equatorial mode
or Ctrl + M ). This will show the area with north up. Select each corner in sequence and
make small changes to the coordinates. Restart Stellarium each time and check if you have moved
into the right direction. Continue with each corner until all the stars match. With a little bit of
practice this will be done in about 10 minutes.

9. Adding Sky Cultures


Stellarium comes with a nice set of skycultures. For ethnographers or historians of science it may
be a worthwile consideration to illustrate the sky culture of the people they are studying. It is not
very hard to do so, but depending on your data, may require some skills in image processing.
Some features regarding translation and multilinguality have evolved over the years, and not
all skycultures currently included in Stellarium adhere to the standards described in the following
sections. If you add a new skyculture, please do so for an optimal result!
In the Stellarium program folder you can see a folder skycultures. Let us assume you work
on Windows and want to create a new Skyculture, say, myCulture.
You can take the inuit directory as template to start with. Just copy the folder C:\Program
Files\Stellarium\skycultures\inuit to C:\Users\[YOU]\AppData\Roaming\Stellarium\
In the folder you see image files for the constellation artwork, and all other files with various
extensions are text files.


Basic Information
In myculture\info.ini, change the entries to
[ info ]
name = myCulture
author = me
boundaries = none
(or what seems best for you). The name is used for the list entry in the Starlore tab in the View
dialog (see 4.4.5).
The option “boundaries” is optional and may contain the follow values:


Chapter 9. Adding Sky Cultures

none — this value is enabled by default and it designates that this culture doesn’t have boundaries
of constellations.
generic — please use this value for subset of “western” cultures to enable using default boundaries.
own — please use it for culture who has own set of boundaries for constellations.


Skyculture Description Files
In order to have translated texts we have files description..utf8, where  is
the two-letter ISO 639-1 language code, or its extension which contains language and country code, like pt_BR for Brazilian Portuguese. A minimum skyculture must contain the file
description.en.utf8, this is en=english text with optional HTML tags for sections, tables,
etc. You can also have embedded images in the HTML (your book cover? Views of sacred landscapes/buildings/artwork/. . . ?), just make them PNG format please. The length of the description
texts is not limited, you have room for a good description, tables of names/translations, links to
external resources, whatever seems suitable. When you started from a copied skyculture, delete the
other description.*.utf8 files.
If you can provide other languages supported by Stellarium, you can provide translations
yourself, else Stellarium translators may translate the English version for you. (It may take years
though.) The file ending .utf8 indicates that for special characters like ÄÖÜßáé you should use
UTF8 encoding. If you write only English/ASCII, this may not be relevant.


Constellation Names
The native constellations are listed in constellation_names.eng.fab. It consists of 3 simple
columns: Abbreviation (or just a serial number), native name, and english translation. The writing
_("name") allows automatic translation of the English strings to other languages. These strings
will be used as constellation labels.
The first column (abbreviation) in the Western sky culture provides the canonical 3-letter
abbreviation for constellations as used by the International Astronomical Union. Such abbreviations
may not be available for the skyculture you are working with, so you must invent your own. These
abbreviations are used as keys in the other files, so they must be unique within your skyculture. It
is not necessary to have 3-letter keys.
The keys can be displayed on screen when labels are requested in the Starlore GUI (section 4.4.5). If you want to prevent certain abbreviations from being displayed, let them start with a
dot. See the effect in the Western (H.A.Rey) skyculture: In Abbreviated mode, only the official
abbreviations are displayed. In Native mode, the second column of constellation_names.eng.fab
is shown. Only with setting Translated , the text translated from the text shown in the third column
is shown. If your skyculture is a variant of the Western skyculture, please use the canonical Latin
names, they have all been translated already.
If your skyculture is not a variant of the generally known Western skyculture, please include an
English translation to the name given in the native language. Else translators will not be able to
translate the name. See a good example in the Mongolian skyculture.


Star Names
The file star_names.fab contains a list of HIP catalogue numbers and common names for those
stars. Each line of the file contains one record of two fields (separated by the pipe character (|)) or
three fields (the first pair is separated by the pipe character (|) and the last one separated by the
space character). The first field is the Hipparcos catalogue number of the star, the second is the

9.5 Planet Names


common name of the star in a format that enables translation support, the third is an optional list of
references (see 9.11) to the source of the information about this name, e.g:
# Piscis Austrinus ( PsA )
113368| _ ( " Fomalhaut " ) 1 ,2 ,6 ,11 ,12
113368| _ ( " Thalim " )
In the sample you can see 3 lines: the first line is a comment, the second line has 3 fields and
the third line has 2 fields. Both lines with data have the same Hipparcos number of the star —
Fomalhaut is the well-known name of HIP 113368, and Thalim is an additional (not well-known)
name of this star.


Planet Names
The file planet_names.fab contains a list of native names of the planets. Each line of the file
contains one record of 3 fields, separated by the white space or tab character. The first field is
the English name of the planet, the second is the native name of the planet (can be in the native
language, but please for maximum utability use an english transliteration) and the third is the
translatable version of the native name of the planet (translated into English). Here is an example
from the Egyptian skyculture:


" Horus - Desher "

_ ( " Red ␣ Horus ␣ ( Mars ) " )

Deep-Sky Objects Names
The file dso_names.fab contains a list of native names for deep-sky objects (DSO). The format
of this file is similar to the star_names.fab format (see 9.4). Each line of the file contains one
record of two fields (separated by the pipe character (|)) or three fields (first pair is separated by the
pipe character (|) and the last one separated by the space character). The first field is an identifier
of the deep-sky object, the second is the native name of the DSO in a format that enables translation
support, the optional third is a list of references (see 9.11) to the source of the information about
this name, e.g.:
PGC 17223| _ ( " Native ␣ name ␣ for ␣ LMC " ) 1 ,2 ,3
NGC 292 | _ ( " Native ␣ name ␣ for ␣ SML " ) 1 ,3
NGC 292 | _ ( " Small ␣ Magellanic ␣ Cloud " )


Stick Figures
The modern-style stick figures are coded in constellationship.fab. Lines look like:
Abbr pairs pair1_star1 pair1_star2 pair2_star1 pair2_star2 ...
In this file,
Abbr is the abbreviation defined in constellation_names.eng.fab
pairs is the number of line pairs which follow.
pairN_starA Hipparcos numbers for the stars which form the constellation stick figure. We need
two entries per line, longer line segments are not supported. To find the HIP number, just
have Stellarium open and click on the star in Stellarium while editing this file.


Chapter 9. Adding Sky Cultures



Constellation Boundaries
The optional file1 constellations_boundaries.dat includes data for the boundary lines drawn
between constellations. The default boundaries for western constellations are defined in the
data/constellations_boundaries.dat file.
The format for this file is a bit more dificult than the other files. It contains sections which may
consist of multiple lines, of the format:
N RA_1 DE_1 RA_2 DE_2 ... RA_N DE_N 2 CON1 CON2
N number of segments for boundary
RA_n, DE_n right ascension (decimal hours) and declination (decimal degrees) of the points of
segments in J2000 coordinates.
2 CON1 CON2 this data indicate “border between 2 constellations CON1 and CON2”. They
are used to define isolated boundaries for each constellation (for proper working of the
Select single constellation option).


Constellation Artwork
Constellation artwork is optional, but may give your skyculture the final touch, if it requires artwork
at all. E.g., H. A. Rey’s variant of the Western skyculture deliberately does not contain artwork.
Each constellation artwork is linked to 3 stars in its constellation. This is programmed in the
file constellationsart.fab. You have to write lines
Abbr image_name . png x1 y1 HIP1 x2 y2 HIP2 x3 y3 HIP3
Abbr is the abbreviation defined in constellation_names.eng.fab
image_name.png is the file name of your texture. It should be sized in a power of two, like
512 × 512, 1024 × 2048 etc. Avoid dimensions larger than 2048, they are not supported on
all systems. You can distort images to better exploit the pixels, the texture will be stretched
back. The background of the artwork image must be absolutely black.
xn, yn, HIPn pixel locations of the star in the constellation drawing (find those in any image
editor) and HIPn is the star number in the Hipparcos catalog, which you find when you click
on the star in Stellarium.
In case the artwork is only available in a certain projection (e.g., an all-sky map), or is otherwise
heavily distorted so that the match is not satisfactory, you may have to reproject the image somehow.
For aligning, you should switch Stellarium to Stereographic projection for optimal results.
You don’t have to shutdown and restart Stellarium during creation/matching, just switch
skyculture to something else and back to the new one to reload.


Seasonal Rules
File seasonal_rules.fab (optional) contains possible seasonal rules for the visibility of constellations. There is one rule per line. Each rule contains three elements separated with white space (or
tab character): constellation ID, start of visibility (month) and end of visibility (month), e.g:
Emu 6 3
1 Please

define “boundaries = own” in the file info.ini to enable using custom boundaries.

9.11 References


This specifies that constellation Emu (abbreviated also as “Emu”) is visible only from June to


The file reference.fab contains a list of information sources. Each line of the file contains one
record of 3 fields, separated by the pipe character (|) — number of source, description of source
and optional URL, e.g.:


9| Kruger 60| https :// en . wikipedia . org / wiki / Kruger_60


Asterisms and help rays
Sometimes there is a need to extract some part of a constellation into a figure in its own right, or to
merge parts from different constellations into one big figure — e.g. “Big Dipper” as part of Ursa
Major or the “Summer Triangle” consisting of 3 stars from the constellations Cygnus, Lyra and
Aquila. Those features are called “asterisms”.
Other simple figures might be used as navigation helpers — the help rays. As example to
help in orientation in sky the additional lines between constellations Ursa Major, Ursa Minor and
Cassiopeia might be useful. The asterisms and help rays are listed in asterism_names.eng.fab.
This file consists of 2 simple columns: Abbreviation (or just a serial number) and English name
of asterism. The writing _("name") allows automatic translation of the English strings to other
languages. These strings will be used as asterisms labels. In addition, after a hash mark (#) marking
a comment sign, some reference information should be noted. Collecting sources and giving such
references is always a good idea. Some later versions of Stellarium may use this information.
The stick figures of asterisms are similar to constellation figures and coded in asterism_lines.fab.
Lines look like:
Abbr type pairs pair1_star1 pair1_star2 pair2_star1 pair2_star2 ...
Abbr 2 pairs pair1_RA1 pair1_DE1 pair1_RA2 pair1_DE2 pair2_RA1 ...
In this file,
Abbr is the abbreviation defined in asterism_names.eng.fab
type is the type of line. Use 1 or 2 to define an asterisms and 0 for the help rays (0 and 1 uses HIP
numbers, and 2 uses coordinates).
pairs is the number of line pairs which follow.
pairN_starA Hipparcos numbers for the stars which form the asterism/help ray stick figure (similar
to constellations), or equatorial coordinates for epoch J2000.0 of the stars (decimal hours for
right ascension and decimal degrees for declination). The help rays are actually a special
form of asterisms in Stellarium.


Publish Your Work
If you are willing to let other users enjoy the result of your hard work (and we certainly hope you
do!), when you are done, please write a note in the Forum or at Launchpad. Please be prepared to
put the imagery and text under some compatible open-source license (Creative Commons). Else the
skyculture cannot be hosted by us.

10. Surveys



A sky survey is a map of the sky stored as a hierarchical set of a potentially large number of smaller
images (called tiles). The advantage compared to a regular texture is that we need to render only
the visible tiles of a potentially gigantic image at the lowest resolution needed. This is particularly
interesting for rendering online images that can be stored on a server, while the client only has to
download the parts he currently uses.
Since version 0.18.0, Stellarium added some preliminary support for loading and rendering online surveys in the Hierarchical Progressive Surveys (HiPS) format, developed by the International
Virtual Observatory Alliance. A full description of the format can be found on the IVOA website1 .


Hipslist file and default surveys
Hipslist files are text files used to describe catalogs of HiPS surveys. The full specification is part
of the HiPS format, and looks like that:
# Example of a hipslist file .
# Date : 2018 -03 -19
h i p s _ s e r v i c e _ u r l = https :// data . stellarium . org / surveys / callisto
h i p s _ r e l e a s e _ d a t e = 2018 -03 -18 T14 :01 Z
= public mirror clonableOnce

As of v0.18.0, by default Stellarium tries to load HiPS from two sources: http://alaskybis. and This can
be changed with the hips/sources options in the configuration file (see also section D.1.27). For



Chapter 10. Surveys

[ hips ]
sources / size = 1
sources /1/ url = " https :// myownhips / hipslist "


Solar system HiPS survey
Though not specified in the HiPS standard, Stellarium recognises HiPS surveys representing planet
textures, as opposed to sky surveys. If the obs_frame property of a survey is set to the name of a
planet or other solar system body, Stellarium will render it in place of the default texture used for
the body.


Extending Stellarium

11 Plugins: An Introduction
12 Interface Extensions

. . . . . . . . . . . . . . . . . . 99

. . . . . . . . . . . . . . . . . . . . . 101

13 Object Catalog Plugins

. . . . . . . . . . . . . . . . . 117

14 Scenery3d – 3D Landscapes . . . . . . . . . . . .
15 Stellarium at the Telescope
16 Scripting


. . . . . . . . . . . . . 159

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

11. Plugins: An Introduction

Starting with version 0.10.3, Stellarium’s packages have included a steadily growing number
of optional extensions called plug-ins: Angle Measure, Compass Marks, Oculars, Telescope
Control, Text User Interface, Satellites, Solar System Editor, Historical Novae and Supernovae,
Quasars, Pulsars, Exoplanets, Observability analysis, ArchaeoLines, Scenery3D, RemoteControl
and RemoteSync. All these plug-ins are “built-in” in the standard Stellarium distribution and don’t
need to be downloaded separately.


Enabling plugins
To enable a plugin:
1. Open the Configuration dialog (press F2 or use the left tool bar button
2. Select the Plugins tab
3. Select the plugin you want to enable from the list
4. Check the Load at startup option
5. Restart Stellarium
If the plugin has configuration options, the configuration button will be enabled when the plugin
has been loaded and clicking it will open the plugin’s configuration dialog. When you only just
activated loading of a plugin, you must restart Stellarium to access the plugin’s configuration dialog.


Data for plugins
Some plugins contain files with different data, e.g., catalogs. JSON is a typical format for those
files, and you can edit its contents manually. Of course, each plugin has a specific format of data for
its own catalogs, and you should read the documentation for the plugin before editing its catalog.
You can read some common instructions for editing catalogs of plugins below. In this example
we use file name catalog.json for identification of the catalog for a typical plugin.


Chapter 11. Plugins: An Introduction

You can modify the catalog.json files manually using a text editor. If you are using
Windows, it is strongly recommended to use an advanced text editor such as Notepad++1 to
avoid problems with end-of-line characters. (It will also color the JSON code and make it easier
to read.)
Warning: Before editing your catalog.json file, make a backup copy. Leaving out the
smallest detail (such as a comma or forgetting to close a curly bracket) may prevent Stellarium
from starting.
As stated in section 5, the path to the directory2 which contains catalog.json file is something
Windows C:\Users\UserName\AppData\Roaming\Stellarium\modules\PluginName
Mac OS X HomeDirectory/Library/Preferences/Stellarium/modules/PluginName
Linux and UNIX-like OS ~/.stellarium/modules/PluginName

2 This

is a hidden folder, so in order to find it you may need to change your computer’s settings to display
hidden files and folders.

12. Interface Extensions

Most users will soon be familiar with the usual user interface. A few plugins are available which
extend the regular user interface with a few small additions which are presented first. However, some
applications and installations of Stellarium require completely different user interfaces. Mostly,
these serve to avoid showing the user interface panels to an audience, be that in your astronomy
club presentations, a domed planetarium or in a museum installation.


Angle Measure Plugin
goes misty eyed
I recall measuring the size of the Cassini Division when I was a student. It was not
the high academic glamor one might expect. . . It was cloudy. . . It was rainy. . . The
observatory lab had some old scopes set up at one end, pointing at a photograph of
Saturn at the other end of the lab. We measured. We calculated. We wished we were
in Hawaii. A picture is worth a thousand words.
The Angle Measure plugin is a small tool which is used to measure the angular distance between
two points on the sky.
1. Enable the tool by clicking the tool-bar button, or by pressing Ctrl + A . A message will
appear at the bottom of the screen to tell you that the tool is active.
2. Drag a line from the first point to the second point using the left mouse button
3. To clear the measurement, click the right mouse button
4. To deactivate the angle measure tool, press the tool-bar button again, or press Ctrl + A on
the keyboard.
In the configuration dialog, you can configure if you want to have distances given on the rotating
sphere, or in horizontal (alt-azimuthal) coordinates. You can also link one point to the resting
horizon, the other to the sky and observe how angles change.

Chapter 12. Interface Extensions



Compass Marks Plugin
Stellarium helps the user get their bearings using the cardinal point feature – the North, South, East
and West markers on the horizon. Compass Marks takes this idea and extends it to add markings
every few degrees along the horizon, and includes compass bearing values in degrees.
When activated (see section 11.1), there is a tool bar button
for toggling the compass
markings. Note that when you enable compass marks, the cardinal points will be turned off.

Figure 12.1: Markings of Compass Marks Plugin

12.3 Equation of Time Plugin



Equation of Time Plugin
































-20 -15 -10 -5






15 20


-20 -15 -10 -5




10 15


Figure 12.2: Figure-8 plots for Equation of Time, for years 1000 (left) and 2000 (right).
These plots, often found on sundials, link solar declination (vertical axis) and its deviation
at mean noon from the meridian, in minutes. Labeled dots indicate when the sun entered
the respective Zodiacal sign (30◦ section of the ecliptic). Figures by Georg Zotti.
The Equation of Time plugin shows the solution of the equation of time. This describes the
discrepancy between two kinds of solar time:
Apparent solar time directly tracks the motion of the sun. Most sundials show this time.
Mean solar time tracks a fictitious “mean” sun with noons 24 hours apart.
There is no universally accepted definition of the sign of the equation of time. Some publications
show it as positive when a sundial is ahead of a clock; others when the clock is ahead of the sundial.
In the English-speaking world, the former usage is the more common, but is not always followed.
Anyone who makes use of a published table or graph should first check its sign usage.
If enabled (see section 11.1), click on the Equation of Time button
to display the value for the equation of time on top of the screen.

on the bottom toolbar

Section EquationOfTime in config.ini file
You can edit config.ini file by yourself for changes of the settings for the Equation of Time
plugin – just make it carefully!









Display solution of the equation of time at startup of Stellarium
Set format for the displayed solution – minutes and seconds
or decimal minutes
Change sign of the equation of time
Show the tool’s button on the bottom toolbar
Font color for the displayed solution of the equation of time
Font size for the displayed solution of the equation of time

Chapter 12. Interface Extensions



Field of View Plugin

Figure 12.3: Configuration dialog of Field of View plugin
By default Stellarium uses smooth zooming via mouse wheel or keyboard shortcuts. Some users may
want stepwise zooming to fixed values for field of view like in the Cartes du Ciel1 planetarium
program, and this plugin provides this feature. You can edit values and use the keyboard for
quick-setting of FOV. All values in degrees.
1. Enable the tool by configuring it to “Load at startup”.
2. Press shortkeys for quick changes of FOV.

Section FOV in config.ini file
You can configure the plugin with its dialog (Fig. 12.3) or edit config.ini file by yourself for
changes of the settings for the Field of View plugin – just make it carefully!






1 SkyChart

Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut
Value of FOV for the shortcut

Ctrl + Alt + 0
Ctrl + Alt + 1
Ctrl + Alt + 2
Ctrl + Alt + 3
Ctrl + Alt + 4
Ctrl + Alt + 5
Ctrl + Alt + 6
Ctrl + Alt + 7
Ctrl + Alt + 8
Ctrl + Alt + 9

/ Cartes du Ciel planetarium:

12.5 Pointer Coordinates Plugin



Pointer Coordinates Plugin

Figure 12.4: Interface of Pointer Coordinates plugin
The Pointer Coordinates plugin shows the coordinates of the mouse pointer. If enabled, click on the
plugin button

on the bottom toolbar to display the coordinates of the mouse pointer.

Section PointerCoordinates in config.ini file
You can edit config.ini file by yourself for changes of the settings for the Pointer Coordinates
plugin – just make it carefully!















Enable displaying mouse pointer coordinates at program startup
Show the plugin’s tool button on the bottom toolbar
Color for coordinates text of the mouse pointer
Font size for the displayed mouse pointer coordinates
Specifies the place of displaying coordinates of
the mouse pointer. Possible values: TopRight,
TopCenter, RightBottomCorner, Custom. Default
value: TopRight.
Specifies the screen coordinates of the custom place
for displaying coordinates of the mouse pointer
Specifies the coordinate system. Possible values:
RaDecJ2000, RaDec, HourAngle, Ecliptic, AltAzi,
Galactic. Default value: RaDecJ2000.
Add the 3-letter IAU abbreviation for the constellation
of the mouse pointer location (Roman, 1987).
Show crossed lines under mouse cursor.

Chapter 12. Interface Extensions



Text User Interface Plugin
This plugin re-implements the “TUI” of the pre-0.10 versions of Stellarium, an unobtrusive menu
used primarily by planetarium system operators to change settings, run scripts and so on.
Given that color configuration for lines and texts cannot be found elsewhere, an interesting part
for general use (at least for extended configuration sessions) is the way to interactively select colors
in this menu.
A full list of the commands for the TUI plugin is given in section 12.6.2.


Using the Text User Interface
1. Activate the text menu using the Alt + T key.2
2. Navigate the menu using the cursors keys.
3. To edit a value, press the right cursor until the value you wish to change it highlighted with
> and < marks, e.g. >3.142<. Then press the cursor keys
to change the value.
You may also type in a new value with the other keys on the keyboard.


TUI Commands

Solar System Body

(menu group)
Set the latitude of the observer in degrees
Set the longitude of the observer in degrees
Set the altitude of the observer in meters
Select the solar system body on which the observer is


Set Time
Current date/time


Set Time Zone
Days keys
Startup date/time preset


Startup date and time


Date Display Format


Time Display Format

(menu group)
Set the time and date for which Stellarium will generate
the view
(disabled in 0.15)
(disabled in 0.15)
Select the time which Stellarium starts with (if the “Sky
Time At Start-up” setting is “Preset Time”
The setting “system” sets Stellarium’s time to the computer clock when Stellarium runs. The setting “preset”
selects a time set in menu item “2.4 - Startup date/time
Change how Stellarium formats date values. “system_default” takes the format from the computer settings, or it is possible to select “yyyymmdd”, “ddmmyyyy” or “mmddyyyy” modes
Change how Stellarium formats time values. “system_default” takes the format from the computer settings, or it is possible to select “24h” or “12h” clock



2 This

(menu group)
Select the sky culture to use (changes constellation lines,
names, artwork)

used to be hard-coded to M before version 0.15, but Alt + T is better to remember as it runs
parallel with Ctrl + T for switching the GUI panels, and frees up M for the Milky Way. The Alt + T
keybinding is hardcoded, i.e., cannot be reconfigured by the user, and should not be used for another function.

12.6 Text User Interface Plugin



Sky Language
App Language

Change the language used to describe objects in the sky
Change the application language (used in GUIs)


Show stars
Relative Scale


Absolute Scale



(menu group)
Turn on/off star rendering
Change the relative brightness of the stars. Larger values
make bright stars much larger.
Change the absolute brightness of the stars. Large values
show more stars. Leave at 1 for realistic views.
Sets how strong the star twinkling effect is - zero is off,
the higher the value the more the stars will twinkle.


Constellation lines
Constellation labels
Art brightness
Constellation boundaries
Cardinal points
Planet labels
Planet orbits
Planet trails
Meridian Line
Azimuthal Grid
Equatorial Grid
Equatorial J2000 Grid
Equator Line
Ecliptic Line
Ecliptic Line (J2000)
Nebula names
Nebula hints
Galaxy hints
Bright nebula hints
Dark nebula hints
Clusters hints
Horizon line
Galactic grid
Galactic equator line
Opposition/conjunction longitude line
Sky background


Light Pollution


(menu group) change color/brightness of the. . .
constellation lines
labels used to name stars
constellation art
constellation boundary lines
cardinal points markers
labels for planets
orbital guide lines for planets
planet trails lines
meridian line
lines and labels for the azimuthal grid
lines and labels for the equatorial grid
lines and labels for the equatorial J2000.0 grid
equator line
ecliptic line
J2000 ecliptic line
labels for nebulae
circles used to mark positions of unspecified nebulae
ellipses used to mark positions of galaxies
squares used to mark positions of bright nebulae
squares used to mark positions of dark nebulae
symbols used to mark positions of clusters
horizon line
galactic grid
galactic equator line
opposition/conjunction line
sky background. Note that anything but black is only
useful for artistic works.

(menu group)
Changes the intensity of the light pollution (see Appendix B Bortle Scale index)
Select the landscape which Stellarium draws when
ground drawing is enabled. Press
to activate.
Setting Landscape Sets Loca- If “Yes” then changing the landscape will move the
observer location to the location for that landscape (if
one is known). Setting this to “No” means the observer
location is not modified when the landscape is changed.

Chapter 12. Interface Extensions




Auto zoom out returns to ini- Changes the behaviour when zooming out from a setial . . . view
lected object. When set to “Off”, selected object will
stay in center. When set to “On”, view will return to
startup view.
Zoom Duration
Sets the time for zoom operations to take (in seconds)
Milky Way intensity
Changes the brightness of the Milky Way
Zodiacal light intensity
Changes the brightness of the Zodiacal light


Run local script


Stop running script


Load default configuration


Save current configuration

(menu group)
Run a script from the scripts sub-directory of the User
Directory or Installation Directory (see section 5 (Files
and Directories))
Stop execution of a currently running script
(menu group)
Reset all settings according to the main configuration
Save the current settings to the main configuration file
Emits a command configured in

Section tui in config.ini file
The section in config.ini for this plugin is named only [tui] for historical reasons. As always,
be careful when editing!









Font color for TUI text
Font size for the TUI
Bend menu text around the screen center. May be
useful in planetarium setups, and should then be used
together with “Disc viewport” in the configuration
menu (see 4.3.4).
Show date and time in lower center.
Show some object info in lower right, or (in planetarium setups with “Disc viewport” active,) wrapped
along the outer circle border.
executable command to shutdown your system. Best
used on Linux or Mac systems. E.g. shutdown -h

12.7 Remote Control Plugin



Remote Control Plugin
The Remote Control plugin enables the user to control Stellarium through an external web interface
using a standard web browser like Firefox or Chrome, instead of using the main GUI. This works
on the same computer Stellarium runs as well as over the network. Even more, multiple “remote
controls” can access the same Stellarium instance at the same time, without getting in the way of
each other. Apart from system configuration options, most of the functionality the main interface
provides is available through it (Zotti, Schaukowitsch, and Wimmer, 2017).
The plugin may be most useful for presentation scenarios, hiding the GUI from the audience
and allowing the presenter to change settings on a separate monitor without showing distracting
dialog windows. It also allows to start and stop scripts remotely. Because the web interface can be
customized (or completely replaced) with some knowledge of HTML, CSS and JavaScript, another
possibility is a kiosk mode, where untrusted users can execute a variety of predefined actions (like
starting recorded tours) without having access to all Stellarium settings. The web API can also be
accessed directly (without using a browser and the HTML interface), allowing control of Stellarium
with external programs and scripts using HTTP calls like with the tools wget and curl.


Using the plugin

Figure 12.5: The default remote control web interface
After enabling the plugin, you can set it up through the configuration dialog. You can configure
it to start the web server automatically whenever Stellarium starts or manually start/stop the server
using the “Server enabled” checkbox or the button
in the toolbar.
The plugin starts an HTTP server on the specified port. The default port is 8090, so you should
reach the remote control after enabling it by starting a web browser on the same computer and
entering http://localhost:8090 in the address bar. When trying to access the remote control
from another computer, you need the IP address or the hostname of the server on which Stellarium
runs. The plugin shows the locally detected address, but depending on your network or if you need
external access you might need to use a different one — contact your network administrator if you
need help with that.


Chapter 12. Interface Extensions

The access to the remote control may optionally be restricted with a simple password.
Warning: currently no network encryption is used, meaning that an attacker having access to
your network can easily find out the password by waiting for a user entering it. Access from the
Internet to the plugin should generally be restricted, except if countermeasures such as VPN usage
are taken! If you are in a home network using NAT (network access translation), this should be
enough for basic security except if port forwarding or a DMZ is configured.

Remote Control Web Interface
If you are familiar with the main Stellarium interface, you should easily find your way around the
web interface. Tabs at the top allow access to different settings and controls.
Main Contains the time controls and most of the buttons of the main bottom toolbar. An additional
control allows moving the view like when dragging the mouse or using the arrow keys in
Stellarium, and a slider enables the changing of the field of view. There are also buttons to
quickly execute time jumps using the commonly used astronomical time intervals.
Selection Allows searching and selecting objects like in section 4.5. SIMBAD search is also
supported. Quick select buttons are available for the primary solar system objects. It also
displays the information text for current selection.
Sky Settings related to the sky display as shown in the “View” dialog as shown in subsection 4.4.1.
DSO The deep-sky object catalog, filter and display settings like in subsection 4.4.3.
Landscape Changing and configuring the background landscape, see subsection 4.4.4
Actions and scripts Lists all registered actions, and allows starting and stopping of scripts (chapter 16). If there is no button for the action you want in another tab, you can find all actions
which can be configured as a keyboard shortcut (section 4.3) here.
Location Allows changing the location, like in section 4.2. Custom location saving is currently
not supported.
Projection Switch the projection method used, like subsection 4.4.3.


Remote Control Commandline API
It is also possible to send commands via command line, e.g.,

-q -- post - data ’ id = show . ssc ’ http :// stella :8090/ api / scripts / run >/ dev / null 2 >&1
-- data ’ id = myScript . ssc ’ http :// localhost :8090/ api / scripts / run >/ dev / null 2 >&1
’ id = myScript . ssc ’ http :// localhost :8090/ api / scripts / run >/ dev / null 2 >&1
-d ’ id = LandscapeMgr . fogDisplayed & value = false ’ \
http :// localhost :8090/ api / stelproperty / set

This allows triggering automatic show setups for museums etc. via some centralized schedulers
like cron.
You can retrieve a complete pretty-printed list of properties:
curl -G -d ’ id = propId = -1& actionId = -2 ’ http :// localhost :8090/ api / main / status | \
python -m json . tool

Depending on your operating system or command shell, you may have to use double quotes in the
--data argument to curl.

Developer information
If you are a developer and would like to add functionality to the Remote Control API, customize
the web interface or access the API through another program, further information can be found in
the plugin’s developer documentation3 .
This plugin was created by Florian Schaukowitsch in the 2015 campaign of the ESA Summer
of Code in Space programme.

12.8 Remote Sync Plugin



Remote Sync Plugin
The Remote Sync plugin enables setups which connect several instances of Stellarium running on a
network. This may be useful in installations where one presenter wants to allow a larger audience
to follow the actions on several dim screens (e.g., when you need to avoid a projector’s bright light
in a public observatory). The actions performed on a “master” instance, which acts as a server, are
automatically replicated on all connected clients. These clients may run on the same device the
server runs, or may access the server over a network.
The plugin is still quite experimental, but is provided for testing purposes. You can configure it
through the standard plugin settings dialog (Figure 12.6). One Stellarium instance can either run in
the server mode or connect to an existing server as a client. A custom TCP protocol is used for the
connection. The port used by the server is configurable, and the clients must know the IP address
or host name and the port of the server.

Figure 12.6: RemoteSync settings window
Alternatively, you may start the plugin through command line arguments. This is useful
for automated setups or when multiple instances are running on the same computer. To start
the instance as a server, use the --syncMode=server argument with the optional --syncPort
parameter to specify the port to listen on. To start a client instance, use --syncMode=client and
use --syncHost and --syncPort to specify the server to connect to.
In the settings window, you can also specify what should happen when the client loses the
connection to its server, and what to do when the server quits normally. You can choose between



Chapter 12. Interface Extensions

Do nothing: connection is lost and will not be re-established. Stellarium client keeps running in
whatever state it was, waiting for keyboard/mouse interaction.
Try reconnecting: Assume Stellarium is switched off on the server but may come back online
again, or assume some temporary network problem. Stellarium client just keeps running in
whatever state it was, but tries to reconnect.
Quit: Assume the server always runs until switched off at the end of operating hours. This is
intended for pure client screens without keyboards. When the server is shut down, assume
this is the end of the day, and exit Stellarium. An enclosing run script can then shutdown the
client computer before power is switched off with some main switch.
By default, the following things are synchronized:
• simulation time
• viewer location
• the selected object
• view direction
• current field of view
• all StelProperty-based settings except for GUI-related properties. This includes almost all
settings visible in the configuration dialogs such as projection type, sky and view options,
landscape settings, line colors, etc.
Because there is currently no full time synchronisation implemented, for the best results all
client computers should make sure their system clocks are set as close as possible to the server
computer’s clock (preferably a few milliseconds difference at most). This can be done for example
by using an NTP server.4 If all your Stellarium instances run on the same device, this is of course
not necessary.
It is also possible to exclude some state from being synchronized. On each client, the client
configuration GUI (Figure 12.7) allows to disable specific settings from being synchronized on this
The lower part of this dialog allows you to fine-tune which named StelProperties (which hold
parts of the internal program state) should be excluded from synchronization. The configuration
dialog lists all available properties which usually have easy to understand names on the left side.
Highlight one or more properties which you don’t want synchronized and press the arrow button to
move them to the list of excluded properties.
For historic reasons there are two kinds of Properties: Actions (Boolean switches, for which
also hotkeys can be assigned) and (genuine) StelProperties. The latter have names indicating which
module they belong to and may have other data types (numbers, colors, . . . ). Note that the actions
frequently are just alias names of Boolean StelProperties, so in order to inhibit a certain property
from being synchronized, you must find both entries.
Properties of plugins will only be visible when the respective plugin has been enabled. When
a plugin has been disabled, its properties may vanish from the stored list of non-synchronized
Each client can have different settings. This could allow installations with several screens
where on one screen you show the constellation figures, another screen shows the distribution of
deep-sky objects in the same frame, and a third screen may show a close-up view of the currently
centered object. Or just show several sky cultures, or show the sky at different locations, . . . .
The names of all available StelProperties from which you might want to select a few to exclude
from synchronisation can also be found with a little scripting (see chapter 16). Open the script
console F12 and enter the following call:
4 Instructions

on how to use the public NTP server pool for the most common operating systems can be
found at

12.8 Remote Sync Plugin


Figure 12.7: RemoteSync client settings window
core . output ( core . getPropertyList ());
Run the script and inspect the output tab. It may take a little guesswork to select the right names,
but the general structure of property names like . should help you to find
your way around.
Author and Acknowledgements
This plugin was created mostly by Florian Schaukowitsch in the 2015-16 campaigns of the ESA
Summer of Code in Space programme.

Chapter 12. Interface Extensions



Solar System Editor Plugin
Stellarium stores its data (orbital elements and other details) about solar system objects (planets,
their moons, minor bodies) in two files. File data/ssystem_major.ini in the installation directory contains data for the planets and their moons. File data/ssystem_minor.ini contains data
for minor bodies, i.e., planetoids and comets. The file will be taken from the user data directory if it
also exists there, which means, users can add minor planets or comets as they become observable
by editing this file.
This plugin provides a window to the Minor Planet Center (MPC5 ) where the latest Solar
System information can be found. When this plugin is loaded (see section 11.1) and you call the
configuration dialog, the first tab allows to import, export or reset your ssystem_minor.ini, and
also to load extra data for minor bodies in Stellarium’s .ini format. For example, the installation
directory contains a file ssystem_1000comets.ini which contains data for over 1000 historical
comets. Currently it is not possible to select only a few from that, so try loading this only on a
reasonably fast computer, and think about deleting comets again (or resetting the file) when you
don’t require them.
The second tab lists all currently loaded minor bodies (see figure 12.9). It is recommended to
remove old entries of yesteryear’s comets if you don’t need them any longer. Just select one or
more objects and press Remove . If you have a very weak computer, you may want to reduce the
number of minor bodies to just a handful to improve performance.
On this tab, you also find the option to connect to the MPC and download current orbital
elements, or load a text file in the format provided by MPC (see figures 12.10 and 12.11).

Figure 12.8: Interface of Solar System Editor plugin: Configuration file tab


12.9 Solar System Editor Plugin

Figure 12.9: Interface of Solar System Editor plugin: Solar System tab

Figure 12.10: Interface of Solar System Editor plugin: Import data dialog



Chapter 12. Interface Extensions

Figure 12.11: Interface of Solar System Editor plugin: Import data dialog — view after
downloading and parsing the MPC data.

13. Object Catalog Plugins

Several plugins provide users with some more object classes.


Bright Novae Plugin

Figure 13.1: Nova Cygni 1975 (also known as V1500 Cyg)
The Bright Novae plugin provides visualization of some bright novae in the Milky Way galaxy. If
enabled (see section 11.1), bright novae from the past will be presented in the sky at the correct
times. For example, set date and time to 30 August 1975, look at the constellation Cygnus to see
Nova Cygni 19751 (Fig. 13.1).

Section Novae in config.ini file
You can edit config.ini file by yourself for changes of the settings for the Bright Novae plugin –
just make it carefully!

Chapter 13. Object Catalog Plugins








Date and time of last update
Frequency of updates, in days
Enable updates of bright novae catalog from Internet
URL of bright novae catalog

Format of bright novae catalog
To add a new nova, open a new line after line 5 and paste the following, note commas and brackets,
they are important:
" Nova ␣ designation " :
" name " : " name ␣ of ␣ nova " ,
" type " : " type ␣ of ␣ nova " ,
" maxMagnitude " : value of maximal visual magnitude ,
" minMagnitude " : value of minimal visual magnitude ,
" peakJD " : JD for maximal visual magnitude ,
" m2 " : Time to decline by 2 mag from maximum ( in days ) ,
" m3 " : Time to decline by 3 mag from maximum ( in days ) ,
" m6 " : Time to decline by 6 mag from maximum ( in days ) ,
" m9 " : Time to decline by 9 mag from maximum ( in days ) ,
" distance " : value of distance between nova and
Earth ( in thousands of Light Years ) ,
" RA " : " Right ␣ ascension ␣ ( J2000 ) " ,
" Dec " : " Declination ␣ ( J2000 ) "
For example, the record for Nova Cygni 1975 (V1500 Cyg) looks like:
" V1500 ␣ Cyg " :
" name " : " Nova ␣ Cygni ␣ 1975 " ,
" type " : " NA " ,
" maxMagnitude " : 1.69 ,
" minMagnitude " : 21 ,
" peakJD " : 2442655 ,
" m2 " : 2 ,
" m3 " : 4 ,
" m6 " : 32 ,
" m9 " : 263
" distance " : 6.36 ,
" RA " : " 21 h11m36 .6 s " ,
" Dec " : " 48 d09m02s "


Light curves
This plugin uses a very simple model for calculation of light curves for novae stars. This model is
based on time for decay by N magnitudes from the maximum value, where N is 2, 3, 6 and 9. If a
nova has no values for decay of magnitude then this plugin will use generalized values for it.

13.2 Historical Supernovae Plugin



Historical Supernovae Plugin

Figure 13.2: Supernova 1604 (also known as Kepler’s Supernova, Kepler’s Nova or
Kepler’s Star)
Similar to the Historical Novae plugin (section 13.1), the Historical Supernovae plugin provides
visualization of bright historical supernovae (Fig. 13.2) from the table below. If enabled (see
section 11.1), bright supernovae from the past will be presented in the sky at the correct times. For
example, set date and time to 29 April 1006, and look at the constellation Lupus to see SN 1006A.

List of supernovae in default catalog

Date of max. brightness

Max. apparent mag.


SN 185A2

7 December



SN 386A

24 April



29 April



SN 1054A4

3 July



SN 1181A5

4 August



SN 1572A6

5 November



Tycho’s Supernova

SN 1604A7

8 October



Kepler’s Supernova





Chapter 13. Object Catalog Plugins

SN 1680A8

15 August



Cassiopeia A

SN 1885A9

17 August



S Andromedae

SN 1895B

5 July



SN 1919A

14 March



SN 1920A
SN 1921C

17 December
11 December



SN 1937C
SN 1937D

21 August
15 September



SN 1960F
SN 1960R
SN 1961H
SN 1962M
SN 1965I
SN 1966J
SN 1968L

21 April
19 December
8 May
26 November
19 Juni
2 December
12 July



SN 1970G
SN 1971I
SN 1972E10
SN 1974G
SN 1979C

30 July
29 May
8 May
27 April
15 April



SN 1980K
SN 1981B
SN 1983N
SN 1986G
SN 1987A11
SN 1989B

31 October
9 March
17 July
12 May
24 February
6 February


Ia Pec

SN 1991T
SN 1993J12
SN 1994ae
SN 1994D
SN 1998bu

26 April
30 March
12 January
31 March
21 May



SN 2004dj
SN 2004et

31 July
2 October



SN 2011fe13
SN 2012cg
SN 2012fr
SN 2013aa
SN 2014j

13 September
6 Juni
16 November
13 February
30 January




13.2 Historical Supernovae Plugin
SN 2017cbv

22 March



Light curves
In this plugin a simple model of light curves for different supernovae has been implemented
(Figure 13.3). While Type I supernovae show a peak and slow but steady decay, Type II supernovae
show a longer “plateau” in the decay curve.

Figure 13.3: Light Curves of Supernovae Types I (left) and II (right)
In both images for light curves the maximum brightness is marked as day 0.

Section Supernovae in config.ini file
You can edit config.ini file by yourself for changes of the settings for the Historical Supernovae
plugin – just make it carefully!


Date and time of last update
Frequency of updates, in days
Enable updates of bright novae catalog from Internet
URL of bright novae catalog


Chapter 13. Object Catalog Plugins

Format of historical supernovae catalog
To add a new nova, open a new line after line 5 and paste the following, note commas and brackets,
they are important:
" Supernova ␣ designation " :
" type " : " type ␣ of ␣ supernova " ,
" maxMagnitude " : value of maximal visual magnitude ,
" peakJD " : JD for maximal visual magnitude ,
" alpha " : " Right ␣ ascension ␣ ( J2000 ) " ,
" delta " : " Declination ␣ ( J2000 ) " ,
" distance " : value of distance between supernova and
Earth ( in thousands of Light Years ) ,
" note " : " notes ␣ for ␣ supernova "
For example, the record for SN 1604A (Kepler’s Supernova) looks like:
" 1604 A " :
" type " : " I " ,
" maxMagnitude " : -2 ,
" peakJD " : 2307190 ,
" alpha " : " 17 h30m36 .00 s " ,
" delta " : " -21 d29m00 .0 s " ,
" distance " : 14 ,
" note " : " Kepler ’ s ␣ Supernova "

13.3 Exoplanets Plugin



Exoplanets Plugin

Figure 13.4: Planetary system τ Ceti
This plugin plots the position of stars with exoplanets. Exoplanets data is derived from “The
Extrasolar Planets Encyclopaedia”14 . List of potential habitable exoplanets and data about them
were taken from “The Habitable Exoplanets Catalog”15 by the Planetary Habitability Laboratory16 .
If enabled (see section 11.1), just click on the Exoplanet button
on the bottom toolbar to
display markers for the stars with known exoplanets. You can then either click on such a marked
star or find the stars with exoplanets by their designation (e.g., 24 Sex) in the F3 dialog (see 4.5).

Potential habitable exoplanets
This plugin can display potential habitable exoplanets (orange marker) and some information about
those planets.
Planetary Class Planet classification from host star spectral type (F, G, K, M; see section 18.2.4),
habitable zone (hot, warm, cold) and size (miniterran, subterran, terran, superterran, jovian,
neptunian) (Earth = G-Warm Terran).
Equilibrium Temperature The planetary equilibrium temperature17 is a theoretical temperature
(in ◦ C) that the planet would be at when considered simply as if it were a black body being
heated only by its parent star (assuming a 0.3 bond albedo). As example the planetary
equilibrium temperature of Earth is -18.15◦ C (255 K).
Earth Similarity Index (ESI) Similarity to Earth18 on a scale from 0 to 1, with 1 being the
most Earth-like. ESI depends on the planet’s radius, density, escape velocity, and surface


Chapter 13. Object Catalog Plugins

Proper names
In December 2015, the International Astronomical Union (IAU) has officially approved names for
several exoplanets after a public vote.
Veritate * (14 And) – From the latin Veritas, truth. The ablative form means where there is truth19 .
Spe * (14 And b) – From the latin Spes, hope. The ablative form means where there is hope.
Musica (18 Del) – Musica is Latin for music.
Arion (18 Del b) – Arion was a genius of poetry and music in ancient Greece. According to
legend, his life was saved at sea by dolphins after attracting their attention by the playing of
his kithara.
Fafnir (42 Dra) – Fafnir was a Norse mythological dwarf who turned into a dragon.
Orbitar (42 Dra b) – Orbitar is a contrived word paying homage to the space launch and orbital
operations of NASA.
Chalawan (47 UMa) – Chalawan is a mythological crocodile king from a Thai folktale.
Taphao Thong (47 UMa b) – Taphao Thong is one of two sisters associated with the Thai folk
tale of Chalawan.
Taphao Kaew (47 UMa c) – Taphao Kae is one of two sisters associated with the Thai folk tale of
Helvetios (51 Peg) – Helvetios is Celtic for the Helvetian and refers to the Celtic tribe that lived in
Switzerland during antiquity.
Dimidium (51 Peg b) – Dimidium is Latin for half, referring to the planet’s mass of at least half
the mass of Jupiter.
Copernicus (55 Cnc) – N ICOLAUS C OPERNICUS or M IKOLAJ KOPERNIK (1473-1543) was a
Polish astronomer who proposed the heliocentric model of the solar system in his book “De
revolutionibus orbium coelestium”.
Galileo (55 Cnc b) – G ALILEO G ALILEI (1564-1642) was an Italian astronomer and physicist
often called the father of observational astronomy and the father of modern physics. Using
a telescope, he discovered the four largest satellites of Jupiter, and the reported the first
telescopic observations of the phases of Venus, among other discoveries.
Brahe (55 Cnc c) – T YCHO B RAHE (1546-1601) was a Danish astronomer and nobleman who
recorded accurate astronomical observations of the stars and planets. These observations
were critical to Kepler’s formulation of his three laws of planetary motion.
Lipperhey * (55 Cnc d) – H ANS L IPPERHEY (1570-1619) was a German-Dutch lens grinder
and spectacle maker who is often attributed with the invention of the refracting telescope in
160820 .
Janssen (55 Cnc e) – JACHARIAS JANSSEN (1580s-1630s) was a Dutch spectacle maker who
is often attributed with invention of the microscope, and more controversially with the
invention of the telescope.
Harriot (55 Cnc f) – T HOMAS H ARRIOT (ca. 1560-1621) was an English astronomer, mathematician, ethnographer, and translator, who is attributed with the first drawing of the Moon
through telescopic observations.
Amateru * (ε Tau b) – Amateru is a common Japanese appellation for shrines when they enshrine
Amaterasu, the Shinto goddess of the Sun, born from the left eye of the god Izanagi21 .
Hypatia (ι Dra b) – H YPATIA was a famous Greek astronomer, mathematician, and philosopher.
She was head of the Neo-Platonic school at Alexandria in the early 5th century, until
19 The

original name proposed, Veritas, is that of an asteroid important for the study of the solar system.
original spelling of Lippershey was corrected to Lipperhey on 15.01.2016. The commonly seen
spelling Lippershey (with an s) results in fact from a typographical error dating back from 1831, thus should
be avoided.
21 The name originally proposed, Amaterasu, is already used for an asteroid.
20 The

13.3 Exoplanets Plugin


murdered by a Christian mob in 415.
Ran * (ε Eri) – Ran is the Norse goddess of the sea, who stirs up the waves and captures sailors
with her net.
AEgir * (ε Eri b) – Ægir is Ran’s husband, the personified god of the ocean. Ægir and Ran both
represent the Jotuns who reign in the outer Universe; together they had nine daughters22 .
Tadmor * (γ Cep b) – Ancient Semitic name and modern Arabic name for the city of Palmyra, a
UNESCO World Heritage Site.
Dagon (α PsA b) – Dagon was a Semitic deity, often represented as half-man, half-fish.
Tonatiuh (HD 104985) – Tonatiuh was the Aztec god of the Sun.
Meztli (HD 104985 b) – Meztli was the Aztec goddess of the Moon.
Ogma * (HD 149026) – Ogma was a deity of eloquence, writing, and great physical strength in
the Celtic mythologies of Ireland and Scotland, and may be related to the Gallo-Roman deity
Ogmios23 .
Smertrios (HD 149026 b) – Smertrios was a Gallic deity of war.
Intercrus (HD 81688) – Intercrus means between the legs in Latin style, referring to the star’s
position in the constellation Ursa Major.
Arkas (HD 81688 b) – Arkas was the son of Callisto (Ursa Major) in Greek mythology.
Cervantes (µ Ara) – Miguel de Cervantes Saavedra (1547-1616) was a famous Spanish writer
and author of “El Ingenioso Hidalgo Don Quixote de la Mancha”.
Quijote (µ Ara b) – Lead fictional character from C ERVANTES’s “El Ingenioso Hidalgo Don
Quixote de la Mancha”.
Dulcinea (µ Ara c) — Fictional character and love interest of Don Quijote (or Quixote) in
C ERVANTES’s “El Ingenioso Hidalgo Don Quixote de la Mancha”.
Rocinante (µ Ara d) – Fictional horse of Don Quijote in C ERVANTES’s “El Ingenioso Hidalgo
Don Quixote de la Mancha”.
Sancho (µ Ara e) – Fictional squire of Don Quijote in C ERVANTES’s “El Ingenioso Hidalgo Don
Quixote de la Mancha”.
Thestias * (β Gem b) – Thestias is the patronym of Leda and her sister Althaea, the daughters of
Thestius. Leda was a Greek queen, mother of Pollux and of his twin Castor, and of Helen
and Clytemnestra24 .
Lich (PSR B1257+12) – Lich is a fictional undead creature known for controlling other undead
creatures with magic.
Draugr (PSR B1257+12 b) – Draugr refers to undead creatures in Norse mythology.
Poltergeist (PSR B1257+12 c) – Poltergeist is a name for supernatural beings that create physical
disturbances, from German for noisy ghost.
Phobetor (PSR B1257+12 d) – Phobetor is a Greek mythological deity of nightmares, the son of
Nyx, the primordial deity of night.
Titawin (υ And) – Titawin (also known as Medina of Tetouan) is a settlement in northern Morocco
and UNESCO World Heritage Site. Historically it was an important point of contact between
two civilizations (Spanish and Arab) and two continents (Europe and Africa) after the 8th
Saffar (υ And b) – Saffar is named for A BU AL -Q ASIM A HMED I BN -A BD A LLAH I BN -O MAR
AL G HAFIQI I BN - AL -S AFFAR , who taught arithmetic, geometry, and astronomy in 11th
century Cordova in Andalusia (modern Spain), and wrote an influential treatise on the uses
22 Note

the typographical difference between Ægir and Aegir, the Norwegian transliteration. The same
name, with the spelling Aegir, has been attributed to one of Saturn’s satellites, discovered in 2004.
23 Ogmios is a name already attributed to an asteroid.
24 The original proposed name Leda is already attributed to an asteroid and to one of Jupiter’s satellites.
The name Althaea is also attributed to an asteroid.

Chapter 13. Object Catalog Plugins


of the astrolabe.
Samh (υ And c) – Samh is named for A BU AL -Q ASIM ’A SBAGH IBN M UHAMMAD IBN AL S AMH AL -M AHRI (or Ibn al-Samh), a noted 11th century astronomer and mathematician in
the school of al Majriti in Cordova (Andalusia, now modern Spain).
Majriti (υ And d) – Majriti is named for A BU AL -Q ASIM AL -Q URTUBI AL -M AJRITI, a notable
mathematician, astronomer, scholar, and teacher in 10th century and early 11th century
Andalusia (modern Spain).
Libertas * (ξ Aql) – Libertas is Latin for liberty. Liberty refers to social and political freedoms,
and a reminder that there are people deprived of liberty in the world even today. The
constellation Aquila represents an eagle – a popular symbol of liberty.
Fortitudo * (ξ Aql b) – Fortitudo is Latin for fortitude. Fortitude means emotional and mental
strength in the face of adversity, as embodied by the eagle (represented by the constellation
All names with asterix mark (*) are modified based on the original proposals, to be consistent
with the IAU rules.

Section Exoplanets in config.ini file
You can edit config.ini file by yourself for changes of the settings for the Exoplanets plugin –
just make it carefully!













Date and time of last update
Frequency of updates, in hours
Enable updates of exoplanets catalog from Internet
URL of exoplanets catalog
Enable showing button of exoplanets on bottom
Enable distribution mode of display
Enable timeline mode of display
Enable habitable mode of display
Enable displaying exoplanets at startup of the
Color for marker of star with planetary system
Color for marker of star with planetary system
with potential habitable exoplanets
Temperature scale for equilibrium temperature
of exoplanets. Possible values: Kelvin, Celsius,
Fahrenheit. Default value: Celsius.

13.3 Exoplanets Plugin


Format of exoplanets catalog
To add a new exoplanet system, open a new line after line 5 and paste the following, note commas
and brackets, they are important:
" Star ␣ designation " :
" exoplanets " :
" mass " : mass of exoplanet ( M jup ) ,
" radius " : radius of exoplanet ( R jup ) ,
" period " : period of exoplanet ( days ) ,
" semiAxis " : semi - major axis ( AU ) ,
" eccentricity " : orbit ’ s eccentricity ,
" inclination " : orbit ’ s inclination ( degree ) ,
" angleDistance " : angle distance from star
( arcseconds ) ,
" discovered " : exoplanet discovered year ,
" detectionMethod " : " exoplanet ␣ detection ␣ method " ,
" pclass " : " planetary ␣ class " ,
" EqTemp " : equilibrium temperature ( K ) ,
" conservative " : conservative or optimistic
habitability of the exoplanet ,
" ESI " : Earth Similarity Index (*100) ,
" planetProperName " : " proper ␣ name ␣ of ␣ planet " ,
" planetName " : " designation ␣ of ␣ planet "
" mass " : mass of exoplanet ( M jup ) ,
" radius " : radius of exoplanet ( R jup ) ,
" period " : period of exoplanet ( days ) ,
" semiAxis " : semi - major axis ( AU ) ,
" eccentricity " : orbit ’ s eccentricity ,
" inclination " : orbit ’ s inclination ( degree ) ,
" angleDistance " : angle distance from star
( arcseconds ) ,
" discovered " : exoplanet discovered year ,
" detectionMethod " : " exoplanet ␣ detection ␣ method " ,
" pclass " : " planetary ␣ class " ,
" EqTemp " : equilibrium temperature ( K ) ,
" conservative " : conservative or optimistic
habitability of the exoplanet ,
" ESI " : Earth Similarity Index (*100) ,
" planetProperName " : " proper ␣ name ␣ of ␣ planet " ,
" planetName " : " designation ␣ of ␣ planet "
" distance " : value of distance to star ( pc ) ,
" stype " : " spectral ␣ type ␣ of ␣ star " ,
" smass " : value of mass of star ( M sun ) ,

Chapter 13. Object Catalog Plugins


" smetal " : value of metallicity of star ,
" Vmag " : value of visual magnitude of star ,
" sradius " : value of radius of star ( R sun ) ,
" effectiveTemp " : value of effective temperature
of star ( K ) ,
" starProperName " : " proper ␣ name ␣ of ␣ the ␣ star " ,
" hasHP " : boolean ( has potential habitable planets ) ,
" RA " : " Right ␣ ascension ␣ ( J2000 ) " ,
" DE " : " Declination ␣ ( J2000 ) "
For example, the record for 24 Sex looks like:
" 24 ␣ Sex " :
" exoplanets " :
" mass " : 1.99 ,
" period " : 452.8 ,
" semiAxis " : 1.333 ,
" eccentricity " : 0.09 ,
" angleDistance " : 0.017821 ,
" discovered " : 2010 ,
" planetName " : " b "
" mass " : 0.86 ,
" period " : 883.0 ,
" semiAxis " : 2.08 ,
" eccentricity " : 0.29 ,
" angleDistance " : 0.027807 ,
" discovered " : 2010 ,
" planetName " : " c "
" distance " : 74.8 ,
" stype " : " G5 " ,
" smass " : 1.54 ,
" smetal " : -0.03 ,
" Vmag " : 7.38 ,
" sradius " : 4.9 ,
" effectiveTemp " : 5098 ,
" RA " : " 10 h23m28s " ,
" DE " : " -00 d54m08s "

13.4 Pulsars Plugin



Pulsars Plugin

Figure 13.5: PSR J0332-5434
This plugin plots the position of various pulsars, with object information about each one. Pulsar
data is derived from “The Australia Telescope National Facility Pulsar Catalogue” (Manchester
et al., 2005).
If enabled (see section 11.1), use the
button to activate display of pulsars. The GUI
allows a few configuration options. You can also find a pulsar ( F3 ) by its designation (e.g., PSR

Section Pulsars in config.ini file





Date and time of last update
Frequency of updates [days]
Enable updates of pulsars catalog from Internet
URL of pulsars catalog
Enable displaying of pulsars at startup of Stellarium
Enable distribution mode for the pulsars
Enable displaying pulsars button on toolbar
Color for marker of the pulsars
Color for marker of the pulsars with glitches
Use separate colors for different types of the pulsars


Chapter 13. Object Catalog Plugins

Format of pulsars catalog
To add a new pulsar, open a new line after line 5 and paste the following, note commas and brackets,
they are important:
" Pulsar ␣ designation " :
" RA " : " Right ␣ ascension ␣ ( J2000 ) " ,
" DE " : " Declination ␣ ( J2000 ) " ,
" notes " : " type ␣ of ␣ pulsar " ,
" distance " : value of distance based on electron density
model ( kpc ) ,
" period " : value of barycentric period of the pulsar ( s ) ,
" parallax " : value of annular parallax ( mas ) ,
" bperiod " : value of binary period of pulsar ( days ) ,
" pderivative " : value of time derivative of barcycentric
period ,
" dmeasure " : value of dispersion measure ( pc /( cm * cm * cm )) ,
" frequency " : value of barycentric rotation frequency ( Hz ) ,
" pfrequency " : value of time derivative of barycentric
rotation frequency (1/( s * s ))
" eccentricity " : value of eccentricity ,
" w50 " : value of profile width at 50% of peak ( ms ) ,
" s400 " : value of time averaged flux density at
400 MHz ( mJy ) ,
" s600 " : value of time averaged flux density at
600 MHz ( mJy ) ,
" s1400 " : value of time averaged flux density at
1400 MHz ( mJy )
For example, the record for PSR J0014+4746 looks like:
" PSR ␣ J0014 +4746 " :
" distance " : 1.82 ,
" dmeasure " : 30.85 ,
" frequency " : 0.805997239145 ,
" pfrequency " : -3.6669 E -16 ,
" w50 " : 88.7 ,
" s400 " : 14 ,
" s600 " : 9 ,
" s1400 " : 3 ,
" RA " : " 00 h14m17 .75 s " ,
" DE " : " 47 d46m33 .4 s "

13.5 Quasars Plugin



Quasars Plugin
The Quasars plugin provides visualization of some quasars brighter than 16 visual magnitude. The
catalogue of quasars has been compiled from “A catalogue of quasars and active nuclei: 13th
edition” (Véron-Cetty and Véron, 2010).

Figure 13.6: 3C 249.1, also known as LEDA 2821945 or 4C 77.09
If enabled (see section 11.1), use the
button to activate display of quasars. The GUI allows
a few configuration options. You can also find a quasar ( F3 ) by its designation (e.g., 3C 273).

Section Quasars in config.ini file





Date and time of last update
Frequency of updates, in days
Enable updates of quasars catalog from Internet
URL of quasars catalog
Enable displaying of quasars at startup of Stellarium
Enable distribution mode for the quasars
Enable displaying quasars button on toolbar
Color for marker of the quasars


Chapter 13. Object Catalog Plugins

Format of quasars catalog
To add a new quasar, open a new line after line 5 and paste the following, note commas and brackets,
they are important:
" Quasar ␣ designation " :
" RA " : " Right ␣ ascension ␣ ( J2000 ) " ,
" DE " : " Declination ␣ ( J2000 ) " ,
" Amag " : value of absolute magnitude ,
" Vmag " : value of visual magnitude ,
" z " : value of Z ( redshift ) ,
" bV " : value of B - V colour
For example, the record for 3C 249.1 looks like:
" 3 C ␣ 249.1 " :
" RA " : " 11 h04m13 .8 s " ,
" DE " : " +76 d58m58s " ,
" Amag " : -25.1 ,
" Vmag " : 15.72 ,
" z " : 0.313 ,
" bV " : -0.02

13.6 Meteor Showers Plugin



Meteor Showers Plugin

Figure 13.7: The 1833 Leonids replayed with the Meteor Showers plugin.
In contrast and extension of the random shooting stars feature of Stellarium (see section 18.6),
this plugin provides data for real meteor showers and a marker for each active and inactive radiant,
showing real information about its activity. If enabled (see section 11.1), just click on the Meteor
Showers button

on the bottom toolbar to display markers for the radiants.

Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate, or
originate, from one point in the night sky. These meteors are caused by streams of cosmic debris
called meteoroids entering Earth’s atmosphere at extremely high speeds on parallel trajectories.
Most meteors are smaller than a grain of sand, so almost all of them disintegrate and never hit
the Earth’s surface. Intense or unusual meteor showers are known as meteor outbursts and meteor
storms, which may produce greater than 1,000 meteors an hour.
The radiant or apparent radiant of a meteor shower is the point in the sky from which (to a planetary
observer) meteors appear to originate. The Perseids, for example, are meteors which appear to
come from a point within the constellation of Perseus.
An observer might see such a meteor anywhere in the sky but the direction of motion, when
traced back, will point to the radiant. A meteor that does not point back to the known radiant for a
given shower is known as a sporadic and is not considered part of that shower.
Many showers have a radiant point that changes position during the interval when it appears.
For example, the radiant point for the Delta Aurigids drifts by more than a degree per night.

Chapter 13. Object Catalog Plugins


Zenithal Hourly Rate (ZHR)
The Zenithal Hourly Rate (ZHR) of a meteor shower is the number of meteors a single observer
would see in one hour under a clear, dark sky (limiting apparent magnitude of 6.5) if the radiant
of the shower were at the zenith. The rate that can effectively be seen is nearly always lower and
decreases the closer the radiant is to the horizon.
Population index
The population index indicates the magnitude distribution of the meteor showers. Values below
2.5 correspond to distributions where bright meteors are more frequent than average, while values
above 3.0 mean that the share of faint meteors is larger than usual.

Section MeteorShowers in config.ini file
You can edit config.ini file by yourself for changes of the settings for the Meteor Showers
plugin – just make it carefully!

















Date and time of last update
Frequency of updates, in hours
Enable updates of the meteor showers catalog from Internet
URL of the meteor showers catalog
Enable showing button of the meteor showers on bottom
Enable displaying markers for the radiants of the meteor
Flag for displaying markers for the radiants of the active
meteor showers only
Enable displaying meteor showers at starup plugin
Flag for displaying labels near markers of the radiants of
the meteor showers
Font size for label of markers of the radiants of the meteor
Color for marker of active meteor showers with generic
Color for marker of active meteor showers with real data
Color for marker of inactive meteor showers

13.6 Meteor Showers Plugin


Format of Meteor Showers catalog
To add a new meteor shower, you just need to:
1. Copy the code of some valid meteor shower;
2. Paste it in the line 6 (right after the "showers": {) of the showers.json document;
3. Replace the information according with your needs.
Note commas and brackets, they are very important! For example, below is a record for Northern
" NTA " :
" designation " : " Northern ␣ Taurids " ,
" activity " :
" year " : " generic " ,
" zhr " : 5 ,
" start " : " 09.25 " ,
" finish " : " 11.25 " ,
" peak " : " 11.12 "
" year " : " 2014 " ,
" start " : " 10.20 " ,
" finish " : " 12.10 "
" year " : " 2013 " ,
" start " : " 10.20 " ,
" finish " : " 12.10 "
" year " : " 2012 " ,
" start " : " 10.20 " ,
" finish " : " 12.10 "
" year " : " 2011 " ,
" start " : " 10.20 " ,
" finish " : " 12.10 "
" speed " : 29 ,
" radiantAlpha " : " 58 " ,
" radiantDelta " : " +22 " ,
" driftAlpha " : " 5 " ,
" driftDelta " : " 1 " ,
" colors " :
" color " : " yellow " ,

Chapter 13. Object Catalog Plugins


" intensity " : 80
" color " : " white " ,
" intensity " : 20
" parentObj " : " Comet ␣ C /1917 ␣ F1 ␣ ( Mellish ) " ,
" pidx " : 2.3


Further Information
You can get more info about meteor showers here:
• Wikipedia about Meteor showers:
• International Meteor Organization:
This plugin was created as project of ESA Summer of Code in Space 201325 .


13.7 Navigational Stars Plugin



Navigational Stars Plugin

Figure 13.8: Navigational stars on the screen
This plugin marks navigational stars from a selected set:
Anglo-American — the 57 "selected stars" that are listed in The Nautical Almanac26 jointly
published by Her Majesty’s Nautical Almanac Office and the US Naval Observatory since
1958; consequently, these stars are also used in navigational aids such as the 2102-D Star
Finder27 and Identifier.
French — the 81 stars that are listed in the Ephémérides Nautiques published by the French
Bureau des Longitudes.
Russian — the 160 stars that are listed in the Russian Nautical Almanac.
on the bottom toolbar to display
If enabled (see section 11.1), just click on the Sextant button
markers for the navigational stars. This can help you in training your skills in astronomical
navigation before you cruise the ocean in the traditional way, with your sextant and chronometer.

Section NavigationalStars in config.ini file
You can edit config.ini file by yourself for changes of the settings for the Navigational Stars
plugin – just make it carefully!





Color of markers of navigational stars
Set to true to display navigational stars at startup of planetarium
Current set of navigational stars. Possible values: AngloAmerican,
French and Russian.

26 The

Nautical Almanac website –
Starfinder 2102-D description and usage instruction – http://oceannavigation.blogspot.
27 Rude

Chapter 13. Object Catalog Plugins



Satellites Plugin
The Satellites plugin displays the positions of artifical satellites in Earth’s orbit based on a catalog
of orbital data. It allows automatic updates from online sources and manages a list of update file
To calculate satellite positions, the plugin uses an implementation of the SGP4/SDP4 algorithms
(J.L. Canales’ gsat library), using as its input data in NORAD’s two-line element set (TLE28 )
format. Lists with TLEs for hundreds of satellites are available online and are regularly updated.
The plugin downloads the lists prepared by to keep itself up-to-date, but
the users can specify other sources online or load updates from local files.
If enabled (see section 11.1), just click on the Satellite button
on the bottom toolbar to
display markers for the satellites.
It should now be possible to search for artificial satellites using the regular search dialog ( F3 ).
Note that at any given time, most Satellites will be below the horizon.

Figure 13.9: Configuration of the Satellites plugin.


Satellite Properties
Name and identifiers Each satellite has a name. It’s displayed as a label of the satellite hint and
in the list of satellites. Names are not unique though, so they are used only for presentation
Satellite Catalog In the Satellite Catalog satellites are uniquely identified by their NORAD
number, which is encoded in TLEs.
Grouping A satellite can belong to one or more groups such as “amateur”, “geostationary” or
“navigation”. They have no other function but to help the user organize the satellite collection.
Group names are arbitrary strings defined in the Satellite Catalog for each satellite and are
more similar to the concept of tags than a hierarchical grouping. A satellite may also not
belong to any group at all.
By convention, group names are in lowercase. The GUI translates some of the groups used
in the default catalog.
28 TLE:

13.8 Satellites Plugin


Iridium Flares prediction
The Satellite plugin might predict Iridium flares for the current location up to 2 weeks in the future
from the current moment. The calculations of visual magnitude based on standard magnitude,
orientation of satellite and places an observer and Sun. Of course all predictions can be saved in the
CSV file (Figure 13.10).

Figure 13.10: Prediction of Iridium flares in the Satellites plugin.

Satellite Catalog
The satellite catalog is stored on the disk in JSON29 format, in a file named satellites.json. A
default copy is embedded in the plug-in at compile time. A working copy is kept in the user data
To add a new satellite, open a new line after line 5 and paste the following, note commas and
brackets, they are important:
" NORAD ␣ number " :
" name " : " name ␣ of ␣ the ␣ satellite "
" description " : " description ␣ goes ␣ here " ,
" comms " : [
" description " : " downlink ␣ 1 " ,
" frequency " : 437.49 ,
" modulation " : " AFSK ␣ 1200 ␣ bps "
" description " : " downlink ␣ 2 " ,
" frequency " : 145.825
" groups " : [ " group1 " , " group2 " ] ,
" stdMag " : 2.0 ,
" tle1 " : " 1 ␣ 12345 U ␣ 90005 D ␣ ␣ ␣ 0908 0.8523 6265 ␣ ␣ .00000014 ␣ ␣ 00000 -0 ␣ ␣ 20602 -4 ␣ 0 ␣ ␣ 5632 " ,
" tle2 " : " 2 ␣ 12345 ␣ 98.2700 ␣ ␣ 53.2702 ␣ 0011918 ␣ ␣ 71.1776 ␣ 289.0705 ␣ 14.31818920 ␣ ␣ ␣ 653 " ,
" visible " : true


Chapter 13. Object Catalog Plugins

Explanation of the fields:
NORAD number required parameter, surrounded by double quotes ("), followed by a colon (:).
It is used internally to identify the satellite. You should replace the text "NORAD number"
with the first number on both lines of the TLE set (in this case, "12345"). It must match
the number of the satellite in the source you are adding from if you want the TLE to be
automatically updated.
The remaining parameters should be listed between two curly brackets and the closing curly bracket
must be followed by a comma to separate it from the next satellite in the list:
name required parameter. It will be displayed on the screen and used when searching for the
satellite with the Find window. Use the description field for a more readable name if you like.
(The description field can accept HTML tags such as 
(new line), (bold), etc.) description optional parameter, double quoted. Appears when you click on the satellite comms optional parameter, square bracketed list of curly bracketed communications information. groups optional parameter, comma separated list of double quoted group names contained in square brackets. Used for grouping satellites in the drop down box on the config (see above) tle1 required, line 1 of the TLE, must be contained in double quotes and begin with "1 " tle2 required, line 2 of the TLE, must be contained in double quotes and begin with "2 " visible required parameter, set to true if you want to see it, this can be toggled from the configuration window once the satellite is loaded. stdMag optional parameter, contained standard magnitude of satellite. You can edit the tags for a satellite, modify the description and comms data, and even add new satellites. 13.8.4 Configuration The plug-in’s configuration data is stored in Stellarium’s main configuration file. 13.8.5 Sources for TLE data Celestrak 30 used as default update source, it also has TLE lists beyond those included by default in Satellite plug-in 31 Space Track 32 the definitive source, requires signup, operated by United States Department of Defense 30 31 32 13.9 ArchaeoLines Plugin 13.9 141 ArchaeoLines Plugin G EORG Z OTTI Figure 13.11: Declination Lines provided by the ArchaeoLines plugin 13.9.1 Introduction In the archaeoastronomical literature, several astronomically derived orientation schemes are prevalent. Often prehistorical and historical buildings are described as having been built with a main axis pointing to a sunrise on summer or winter solstice. There can hardly be a better tool than Scenery3D (see chapter 14) to investigate a 3D model of such a building, and this plugin has been introduced in version 0.13.3 as a further tool in the archaeoastronomer’s toolbox (Zotti, 2016b). (in the shape of a When activated (see section 11.1), you can find a a tool bar button trilithon with the sun shining through it). Press this, or Ctrl + U , to display the currently selected set of characteristical diurnal arcs. 13.9.2 Characteristic Declinations The ArchaeoLines plugin displays any combination of declination arcs δ most relevant to archaeoor ethnoastronomical studies. Of course, principles used in this context are derived from natural observations, and many of these declinations are still important in everyday astronomy. • Declinations of equinoxes (i.e., the equator, δ = 0) and the solstices (δ = ±ε) √ • Declinations of the crossquarter days (days between solstices and equinoxes, δ = ±ε/ 2) • Declinations of the Major Lunar Standstills (δ = ±(ε + i)) • Declinations of the Minor Lunar Standstills (δ = ±(ε − i)) • Declination of the Zenith passage (δ = ϕ) • Declination of the Nadir passage (δ = −ϕ) • Declination δ of the currently selected object • Current declination δÀ of the sun • Current declination δÁ of the moon • Current declination δP of a naked-eye planet Chapter 13. Object Catalog Plugins 142 Rising Azimuths, Year 2000 75 75 70 70 65 65 60 60 55 55 50 50 45 45 40 40 35 35 30 30 25 25 Solstices, Equinoxes 20 20 Solar Crossquarters 15 10 5 0 0 15 Major Standstills Minor Standstills 10 Zenith Passage 5 Nadir Passage 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 0 180 Figure 13.12: Rising azimuths of a few important events for sun and moon, and zenith and nadir passages depending on geographic latitudes (vertical axis). The principal relation between declinations δ , geographic latitude ϕ, and the rising azimuth A is computed from cos A = − sin δ . cos ϕ (13.1) This formula does not take into account local horizon elevation nor atmospheric refraction nor lunar parallax correction. The effect applied to characteristic declinations is shown graphically for the present time (J2000.0) in figure 13.12. For example, in a latitude of 30◦ , an object which goes through the zenith rises at azimuth 55◦ . Lunar major standstill risings occur at azimuths 56.7◦ and 123.5◦ , lunar minor standstill risings at azimuths 69◦ and 111◦ . The summer sun rises at 62.6◦ , the winter sun at 117.3◦ . An object which goes through the nadir rises at 125◦ . The blue lines seem to vanish at ϕ = 45◦ : while there are still objects going through the zenith in higher latitudes, they are circumpolar and do not cross the horizon. For the lunar events, there are two lines each drawn by the plugin, for maximum and minimum distance of the moon. The lunar extreme declinations are computed taking horizon parallax effects into account. For technical reasons however, the derived declinations are then used to draw small circles of constant declinations on the sphere, without taking the change of lunar horizontal parallax into account. Note that therefore the observed declination of the moon at the major standstill can exceed the indicated limits if it is high in the sky. The main purpose of this plugin is however to show an indication of the intersection of the standstill lines with the horizon. It may be very instructive to let the time run quite fast and observe the declination line of “current moon” swinging between its north and south limits each month. These limits grow and shrink between the Major and Minor Standstills in the course of 18.6 years. 13.9 ArchaeoLines Plugin 143 The sun likewise swings between the solstices. Over centuries, the solstice declinations very slightly move as well due to the slightly changing obliquity of the ecliptic. 13.9.3 Azimuth Lines Some religions, e.g., Islam or Bahai, adhere to a practice of observing a prayer direction towards a particular location. Azimuth lines for two locations can be shown, these lines indicate the great circle direction towards the locations which can be edited in the configuration window. Default locations are Mecca (Kaaba) and Jerusalem. The azimuth q towards a location T = (λT , ϕT ) can be computed for an observer at O = (λO , ϕO ) based on spherical trigonometry on a spherical Earth (Abdali, 1997) as q = arctan sin(λT − λO ) cos ϕO tan ϕT − sinϕO cos(λT − λO ) (13.2) In addition, up to two vertical lines with arbitrary azimuth and custom label can be shown. 13.9.4 13.9.5 Arbitrary Declination Lines Up to two arbitrary declination lines can be shown with a custom label. Configuration Options The configuration dialog allows the selection of the lines which are of interest to you. In addition, you can select the color of the lines by clicking on the color swatches.33   Section ArchaeoLines in config.ini file Apart from changing settings using the plugin configuration dialog, you can also edit config.ini file by yourself for changes of the settings for the ArchaeoLines plugin – just make it carefully! ID Type Default enable_at_startup bool false color_equinox color_solstices color_crossquarters color_major_standstill color_minor_standstill color_zenith_passage color_nadir_passage color_selected_object color_current_sun color_current_moon color_current_planet color_geographic_location_1 color_geographic_location_2 color_custom_azimuth_1 color_custom_azimuth_2 float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B float R,G,B 1.00,1.00,0.50 1.00,1.00,0.25 1.00,0.75,0.25 0.25,1.00,0.25 0.20,0.75,0.20 1.00,0.75,0.75 1.00,0.75,0.75 1.00,1.00,1.00 1.00,1.00,0.75 0.50,1.00,0.50 0.25,0.80,1.00 0.25,1.00,0.25 0.25,0.25,1.00 0.25,1.00,0.25 0.25,0.50,0.75 33 Unfortunately, on some systems with Windows in OpenGL mode, the color dialog hides behind the Stellarium window when in fullscreen mode. So, before editing line colors, please leave fullscreen mode! 0.15.1 Chapter 13. Object Catalog Plugins 144 color_custom_declination_1 color_custom_declination_2 float R,G,B float R,G,B 0.45,1.00,0.15 0.45,0.50,0.65 show_equinox show_solstices show_crossquarters show_major_standstills show_minor_standstills show_zenith_passage show_nadir_passage show_selected_object show_current_sun show_current_moon show_current_planet bool bool bool bool bool bool bool bool bool bool string true true true true true true true true true true none show_geographic_location_1 show_geographic_location_2 geographic_location_1_longitude geographic_location_1_latitude geographic_location_1_label geographic_location_2_longitude geographic_location_2_latitude geographic_location_2_label bool bool double double string double double string false false 39.826175 21.4276 Mecca (Qibla) 35.235774 31.778087 Jerusalem show_custom_azimuth_1 show_custom_azimuth_2 custom_azimuth_1_angle custom_azimuth_2_angle custom_azimuth_1_label custom_azimuth_2_label custom_altitude_1_angle custom_altitude_2_angle custom_altitude_1_label custom_altitude_2_label bool bool double double string string double double string string false false 0.0 0.0 custAzi1 custAzi2 0.0 0.0 custAlt1 custAlt2 show_custom_declination_1 show_custom_declination_2 custom_declination_1_angle custom_declination_1_label custom_declination_2_angle custom_declination_2_label bool bool double string double string false false 0.0 custDec1 0.0 custDec2 14. Scenery3d – 3D Landscapes G EORG Z OTTI AND F LORIAN S CHAUKOWITSCH 14.1 Introduction Have you ever wished to be able to walk through Stonehenge or other ancient building structures described as being constructed with astronomical orientation in mind, and experience such orientation in a 3D virtual environment that also provides a good sky simulation? The Stellarium Scenery3d plugin allows you to see architectural 3D models embedded in a landscape combined with the excellent representation of the sky provided by Stellarium. You can walk around, check for (or demonstrate) possible astronomical alignments of ancient architecture, see sundials and other shadow casters in action, etc. 14.2 Usage You activate the plugin with the circular enclosure button Ctrl + W at screen bottom or by pressing + W ) opens . The other button with circular enclosure and tool icon (or Ctrl + the settings dialog. Once loaded and displaying, you can walk around pressing Ctrl plus cursor key increases speed keys. Change eye height with Ctrl + Page / Ctrl + Page keys. Adding by 10, adding Alt multiplies by 5 (pressing both keys multiplies by 50!). If you release Ctrl before the cursor key, animation will continue. (Press Ctrl +any cursor key to stop moving.) Further key bindings exist which can be configured using the Stellarium default key-binding interface. Some options are also available in the Scenery3d dialog. For example, coordinate display can be enabled with Ctrl + R + T . If your models are georeferenced in a true geographical coordinate grid, e.g. UTM or Gauss-Krueger, you will especially like this, and this makes the plugin usable for scientific purposes. Display shows grid name, Easting, Northing, Altitude of ground, and eye height above ground. Other features include a virtual “torchlight”, which can be enabled with Ctrl + R + L to give 146 Chapter 14. Scenery3d – 3D Landscapes additional local illumination around the viewer to help to see in the dark. Interesting points of view can be saved and restored later by the user, including a description of the view. Scene authors can also distribute predefined viewpoints in their scene. The plugin also simulates the shadows of the scene’s objects cast by the Sun, Moon and even Venus (only 1 shadow caster used at a time, you will never see shadows cast by Venus in moonlight), so you could use it for examining sundials, or analyze and simulate light-and-shadow interactions in archaeological structures. 14.3 Hardware Requirements & Performance In order to work with the non-linear projection models in Stellarium, this plugin uses a trick to create the foreground renderings: it renders the scene into the six planes of a so-called cubemap, which is then correctly reprojected onto the sides of a cube, depending on the current projection settings. Your graphics card must be able to do this, i.e. it must support the OpenGL extension called EXT_framebuffer_object. Typical modern 3D cards (by NVidia or ATI/AMD) support this extension. In case your graphics hardware does not suppport it, the plugin will still work, but you are limited to perspective projection. You can influence rendering quality, but also speed, using the plugin’s GUI, which provides some options such as enabling the use of shadows, bumpmapping (provides more realistic surface lighting) or configuring the sizes of the textures used for the cubemap or shadowmaps. Larger values there improve the quality, but require faster hardware and more video memory for smooth results. Because the “cubemap trick” requires quite a large amount of performance (in essence, the scene has to be rendered 6 times), there are some options available that try to reduce this burden. The first option is to change the type of the “cubemap”. The most compatible setting is 6 textures, which seems to work best on older integrated Intel GPUs. The recommended default is the second setting, Cubemap, which uses a more modern OpenGL feature and generally works a bit faster than 6 textures on more modern graphics cards. Finally, the Geometry shader option tries to render all 6 cube faces at once. This requires a more recent GPU + drivers (at least OpenGL 3.2 must be supported), the setting is disabled otherwise. Depending on your hardware and the scene’s complexity, this method may give a speedup or may be slower, you must find this out yourself. Another option prevents re-rendering of the cubemap if nothing relevant has changed. You can define the interval (in Stellarium’s simulation time) in which nothing is updated in the GUI. You can still rotate the camera without causing a re-draw, giving a subjective performance that is close to Stellarium’s performance without Scenery3d. When moving, the cubemap will be updated. You can enable another option that only causes 1 or 2 sides of the cubemap to be updated while you move, giving a speedup but causing some parts of the image to be outdated and discontinuous. The cubemap will be completed again when you stop moving. Shadow rendering may also cause quite a performance impact. The Simple shadows option can speed this up a lot, at the cost of shadow quality especially in larger scenes. Another performance/quality factor is shadow filtering. The sharpest (and fastest) possible shadows are achieved with filtering Off, but depending on shadowmap resolution and scene size the shadows may look quite “blocky”. Hardware shadow filtering is usually very fast, but may not improve appearance a lot. Therefore, there are additional filter options available, the High filter option is relatively expensive. Finally, the PCSS option allows to approximate the increase of solar and lunar shadow penumbras relative to the distance from their shadow casters, i.e. shadows are sharp near contact points, and more blurred further away. This again requires quite a bit of performance, and only works if the shadow filter option is set to Low or High (without Hardware). The configuration GUI shows tooltips for most of its settings, which can explain what a setting 14.4 Model Configuration 147 Geometry Lights Clay Photomatched DefaultUVs Instanced Yes Yes No Yes No No Table 14.1: Kerkythea Export Settings does. All settings are saved automatically, and restored when you reopen Stellarium. 14.3.1 Performance notes This plugin clearly runs better with proper 3D graphics cards. On reasonably good hardware (tested on a notebook PC with NVidia M960), models with over 10.000.000 triangles are working nicely with shadows and bumpmaps, although your mileage may vary. On very small hardware like single-board computers with native OpenGL ES2, models may be limited to 64k vertices (points). If display is too slow, switch to perspective projection: all other projections require almost sixfold effort! Or try the “lazy” cubemap mode and lazy updates of tiles, where the scene is only rendered in specific timesteps or when movement happens. 14.4 Model Configuration The model format supported in Scenery3d is Wavefront .OBJ, which is pretty common for 3D models. You can use several modeling programs to build your models. Software such as Blender, Maya, 3D Studio Max etc. can export OBJ. 14.4.1 Exporting OBJ from Sketchup A simple to use and cost-free modeling program is Sketchup, commonly used to create the 3D buildings seen in Google Earth. It can be used to create georeferenced models. OBJ is not a native export format for the standard version of Sketchup. If you are not willing to afford Sketchup Pro, you have to find another way to export a textured OBJ model. One good exporter is available in the Kerkythea renderer project1 . You need SU2KT 3.17 or better, and KT2OBJ 1.1.0 or better. Deselect any selection, then export your model to the Kerkythea XML format with settings shown in 14.1. (Or, with selection enabled, make sure settings are NoYes-Yes-No-Yes-No-No.) You do not have to launch Kerkythea unless you want to create nice renderings of your model. Then, use the KT2OBJ converter to create an OBJ. You can delete the XML after the conversion. Note that some texture coordinates may not be exported correctly. The setting Photomatched:Yes seems now to have corrected this issue, esp. with distorted/manually shifted textures. Another free OBJ exporter has been made available by TIG: OBJexporter.rb2 . This is the only OBJ exporter tested so far capable of handling large TIN landscapes (> 450.000 triangles). As of version 2.6 it seems to be the best OBJ exporter available for Sketchup. This exporter swaps Y/Z coordinates, but you can add a key to the config file to correct swapped axes, see below. Other exporters may also provide coordinates in any order of X, Y, Z – all those can be properly configured. 1 Available 2 Available at from 148 Chapter 14. Scenery3d – 3D Landscapes Another quirk has to be fixed manually though: in the material description file (MTL), TIG’s exporter writes both d and Tr lines with the same value. Actually, Tr = 1.0 − d according to OBJ/MTL documentation, so you should edit away one line, or else the later line overwrites the value given earlier. Moreover, given that Tr=1 should actually specify fully transparent objects, such a line will make your object entirely invisible! Another (almost) working alternative: ObjExporter.rb by author Honing. Here, export with settings 0xxx00. This will not create a TX... folder but dump all textures in the same directory as the OBJ and MTL files. Unfortunately, currently some material assignments seem to be bad. 14.4.2 Notes on OBJ file format limitations The OBJ format supported is only a subset of the full OBJ format: Only (optionally textured) triangle meshes are supported, i.e., only lines containing statements: mtllib, usemtl, v, vn, vt, f (with three elements only!), g. Negative vertex numbers (i.e., a specification of relative positions) are not supported. A further recommendation for correct illumination is that all vertices should have vertex normals. Sketchup models exported with the Kerkythea or TIG plugins should have correct normals. If your model does not provide them, default normals can be reconstructed from the triangle edges, resulting in a faceted look. If possible, the model should also be triangulated, but the current loader may also work with non-triangle geometry. The correct use of objects (o) and groups (g) will improve performance: it is best if you pre-combine all objects that use the same material into a single one. The loader will try to optimize it anyways if this is not the case, but can do this only partly (to combine 2 objects with the same material into 1, it requires them to follow directly after each other in the OBJ). A simple guide to use Blender3 for this task follows: 1. File Import Wavefront .obj - you may need to change the forward/up axes for correct orientation, try “-Y forward” and “Z up” 2. Select an object which has a shared material + L and select ’By Material’ 3. Press 4. Select ’Join’ in the left (main) tool window 5. Repeat for other objects that have shared materials 6. Export the .obj, making sure to select the same forward/up axes as in the import, also make sure “Write Normals”, “Write Materials” and “Include UVs” are checked For transparent objects (with a d or Tr value, alpha testing does NOT need this), this recommendation does NOT hold: for optimal results, each separate transparent object should be exported as a separate “OBJ object”. This is because they need to be sorted during rendering to achieve correct transparency. If the objects are combined already, you can separate them using Blender: 1. Import .obj (see above) 2. Select the combined transparent object and make sure everything is selected (press A if not) 3. Enter “Edit” mode with 4. Press P and select “By loose parts”, this should separate the object into its unconnected regions 5. Export .obj (see above), also check “Objects as OBJ Objects” The MTL file specified by mtllib contains the material parameters. The minimum that should be specified is either map_Kd or a Kd line specifying color values used for the respective faces. But there are other options in MTL files, and the supported parameters and defaults are listed in Table 14.2. If no ambient color is specified, the diffuse color values are taken for the ambient color. An optional emissive term Ke can be added, which is modulated to only be visible during nighttime. 3 14.4 Model Configuration 149 Parameter Default Range Meaning Ka Kd Ke Ks Ns d or Tr bAlphatest bBackface map_Kd map_Ke map_bump illum vis_fadeIn vis_fadeOut set to Kd values 0.8 0.8 0.8 0.0 0.0 0.0 0.0 0.0 0.0 8.0 1.0 0 0 (none) (none) (none) 2 (none) (none) 0 . . . 1 each 0 . . . 1 each 0 . . . 1 each 0 . . . 1 each 0...∞ 0...1 0 or 1 0 or 1 filename filename filename integer double double R/G/B Ambient color R/G/B Diffuse color R/G/B Emissive color R/G/B Specular color shinyness opacity perform alpha test render backface texture map to be mixed with Ka, Kd texture map to be mixed with Ke normal map for surface roughness illumination mode in the standard MTL format. see 14.4.5 see 14.4.5 Table 14.2: MTL parameters evaluated This also requires the landscape’s self-illumination layer to be enabled. It allows to model selfilluminating objects such as street lights, windows etc. It can optionally also be modulated by the emissive texture map_Ke. If a value for Ks is specified, specularity is evaluated using the Phong reflection model4 with Ns as the exponential shininess constant. Larger shininess means smaller specular highlights (more metal-like appearance). Specularity is not modulated by the texture maps. Unfortunately, some 3D editors export unusable default value combinations for Ks and Ns. Blender may create lines with Ks=1/1/1 and Ns=0. This creates a look of “partial overexposed snow fields”. While the values are allowed in the specification, in most cases the result looks ugly. Make sure to set Ns to 1 or higher, or disable those two lines. If a value for d or Tr exists, alpha blending is enabled for this material. This simulates transparency effects. Transparency can be further controlled using the alpha channel of the map_Kd texture. A simpler and usually more performant way to achieve simple “cutout” transparency effects is alpha-testing, by setting bAlphatest to 1. This simply discards all pixels of the model where the alpha value of the map_Kd is below the transparency_threshold value from scenery3d.ini, making “holes” in the model. This also produces better shadows for such objects. If required, alpha testing can be combined with “real” blending-based transparency. Sometimes, exported objects only have a single side (“paper wall”), and are only visible from one side when looked at in Scenery3d. This is caused by an optimization called back-face culling, which skips drawing the back sides of objects because they are usually not visible anyway. If possible, avoid such “thin” geometry, this will also produce better shadows on the object. As a workaround, you can also set bBackface to 1 to disable back-face culling for this material. The optional map_bump enables the use of a tangent-space normal maps5 , which provides a dramatic improvement in surface detail under illumination. 4 5 150 14.4.3 Chapter 14. Scenery3d – 3D Landscapes Configuring OBJ for Scenery3d The walkaround in your scene can use a ground level (piece of terrain) on which the observer can walk. The observer eye will always stay “eye height” above ground. Currently, there is no collision detection with walls implemented, so you can easily walk through walls, or jump on high towers, if their platform or roof is exported in the ground layer. If your model has no explicit ground layer, walk will be on the highest surface of the scenery layer. If you use the special name NULL as ground layer, walk will be above zero_ground_height level. Technically, if your model has cavities or doors, you should export your model twice. Once, just the ground plane, i.e. where you will walk. Of course, for a temple or other building, this includes its socket above soil, and any steps, but pillars should not be included. This plane is required to compute eye position above ground. Note that it is not possible to walk in several floors of a building, or in a multi-plane staircase. You may have to export several “ground” planes and configure several scenery directories for those rare cases. For optimal performance, the ground model should consist of as few triangles as you can tolerate. The second export includes all visible model parts, and will be used for rendering. Of course, this requires the ground plane again, but also all building elements, walls, roofs, etc. If you have not done so by yourself, it is recommended to separate ground and buildings into Sketchup layers (or similar concepts in whichever editor you are using) in order to easily switch the model to the right state prior to exporting. Filename recommendations: .skp Name of a Sketchup Model file. (The <> brackets signal “use your own name here!”) The SKP file is not used by Scenery3d, but you may want to leave it in the folder for later improvements. .obj Model in OBJ format. _ground.obj Ground layer, if different from Model file. OBJ export may also create folders TX_ and TX__ground. You can delete the TX__ground folder, _ground.obj is just used to compute vertical height. Put the OBJ, MTL and TX directories into a subdirectory of your user directory (see section 5.1), e.g. /Stellarium/scenery3d/, and add a text file into it called scenery3d.ini (This name is mandatory!) with content described as follows. [model] name= Unique ID within all models in scenery3d directory. Recommendation: use directory name. landscape= Name of an available Stellarium landscape. This is required if the landscape file includes geographical coordinates and your model does not: First, the location coordinates of the landscape.ini file are used, then location coordinates given here. The landscape also provides the background image of your scenery. If you want a zero-height (mathematical) horizon, use the provided landscape called Zero Horizon. scenery=.obj The complete model, including visible ground. ground=_ground.obj Optional: separate ground plane. (NULL for zero altitude.) description= A basic scene description (including HTML tags) The scenery3d.ini may contain a simple scene description, but it is recommended to use the localizable description format: in the scene’s directory (which contains scenery3d.ini) create files in the format description..utf8 which can contain arbitrary UTF-8–encoded HTML content. stands for the ISO 639 language code. author= copyright= 14.4 Model Configuration obj_order=XYZ camNearZ=0.3 camFarZ=10000 shadowDistance= shadowSplitWeight=0..1 151 Use this if you have used an exporter which swaps Y/Z coordinates. Defaults to XYZ, other options: XZY, YZX, YXZ, ZXY, ZYX This defines the distance of the camera near plane, default 0.3. Everything closer than this value to the camera can not be displayed. Must be larger than zero. It may seem tempting to set this very small, but this will lead to accuracy issues. Recommendation is not to go under 0.1 Defines the maximal viewing distance, default 10000. The maximal distance shadows are displayed. If left out, the value from camFarZ is used here. If this is set to a smaller value, this may increase the quality of the shadows that are still visible. Decimal value for further shadow tweaking. If you require better shadows up close, try setting this to higher values. The default is calculated using a heuristic that incorporates scene size. [general] The general section defines some further import/rendering options. transparency_threshold=0.5 Defines the alpha threshold for alpha-testing, as described in section 14.4.2. Default 0.5 scenery_generate_normals=0 Boolean, if true normals are recalculated by the plugin, instead of imported. Default false Boolean, same as above, for ground model. Default false. ground_generate_normals=0 [location] Optional section to specify geographic longitude λ , latitude ϕ, and altitude. The section is required if coord/convergence_angle=from_grid, else location is inherited from landscape. planet = Earth latitude = +48d31’30.4" Required if coord/convergence_angle=from_grid longitude = +16d12’25.5" "–" altitude =from_model| altitude (for astronomical computations) can be computed from the model: if from_model, it is computed as (zmin + zmax )/2 + orig_H, i.e. from the model bounding box centre height. display_fog = 0 atmospheric_extinction_coefficient = 0.2 atmospheric_temperature = 10.0 atmospheric_pressure = -1 light_pollution = 1 [coord] Entries in the [coord] section are again optional, default to zero when not specified, but are required if you want to display meaningful eye coordinates in your survey (world) coordinate system, like UTM or Gauss-Krüger. grid_name= orig_E= | (Easting) Name of grid coordinates, e.g. "UTM 33 U (WGS 84)", "Gauss-Krüger M34" or "Relative to
" This name is only displayed, there is no evaluation of its contents. East-West-distance to zone central meridian Chapter 14. Scenery3d – 3D Landscapes 152 orig_N= | (Northing) orig_H= | (Height) North distance from Equator Altitude above Mean Sea Level of model origin These entries describe the offset, in metres, of the model coordinates relative to coordinates in a geographic grid, like Gauss-Krüger or UTM. If you have your model vertices specified in grid coordinates, do not specify orig_... data, but please definitely add start_... data, below. Note that using grid coordinates without offset for the vertices is usually a bad idea for realworld applications like surveyed sites in UTM coordinates. Coordinate values are often very large numbers (ranging into millions of meters from equator and many thousands from the zone meridian). If you want to assign millimetre values to model vertices, you will hit numerical problems with the usual single-precision floating point arithmetic. Therefore we can specify this offset which is only necessary for coordinate display. Typically, digital elevation models and building structures built on those are survey-grid aligned, so true geographical north for a place with geographical longitude λ and latitude ϕ will in general not coincide with grid north, the difference is known as meridian convergence6 . γ(λ , ϕ) = arctan(tan(λ − λ0 ) sin ϕ) (14.1) This amount can be given in convergence_angle (degrees), so that your model will be rotated clockwise by this amount around the vertical axis to be aligned with True North7 . convergence_angle = from_grid | < double > grid_meridian = < double >|+ < int >d < int > ’ < float > " grid_meridian is the central meridian λ0 of grid zone, e.g. for UTM or Gauss-Krüger, and is only required to compute convergence angle if convergence_angle=from_grid. zero_ground_height = < double > height of terrain outside _ground.OBJ, or if ground=NULL. Allows smooth approach from outside. This value is relative to the model origin, or typically close to zero, i.e., use a Z value in model coordinates, not world coordinates! (If you want the terrain height surrounding your model to be orig_H, use 0, not the correct mean height above sea level!) Defaults to minimum of height of ground level (or model, resp.) bounding box. start_E= start_N= start_H= only meaningful if ground==NULL, else H is derived from ground start_Eye= default: 1.65m start_az_alt_fov=,, initial view direction and field of view. start_... defines the view position to be set after loading the scenery. Defaults to center of model boundingbox. It is advisable to use the grid coordinates of the location of the panoramic photo (landscape) as start_... coordinates, or the correct coordinates and some carefully selected start_az_alt_fov in case of certain view corridors (temple axes, . . . ). 6 7 Note that Sketchup’s georeferencing dictionary provides a NorthAngle entry, which is 360 − convergence_angle. 14.4 Model Configuration 153 14.4.4 Concatenating OBJ files Some automated workflows may involve tiled landscape areas, e.g. to overcome texture limitations or triangle count limits in simpler tools like Sketchup. In this case you can create separate meshes in the same coordinate system, but you need to concatenate them. One powerful program to assemble your parts is again Blender. In Blender, import the OBJ files File Import Wavefront .obj . If your OBJ coordinates have Z as vertical axis (common for terrestrial models), use “Z up”, “-Y Forward” as import settings for the coordinate axes. The model will appear south-up. Switch on textured view if required ( Alt + Z ). If the scene looks almost black now, reconfigure the light to be sunlight. If you have created a VRML of some structures in ArcScene, export that without shifting to center, and import the WRL file in Blender with default orientation “Y up”, “Z forward”. Models from other sources may still be different. In the end, all parts should fit neatly together. Blender is a very powerful program, you can enhance your model as you wish. In the end, select all relevant parts which you want to have visible in Stellarium (click on the lines in the outline view containing the object names to light them up gray, then RightclickSelect) and press Ctrl + J to optionally join them, then export to a single OBJ File Export Wavefront .obj . In the export options, apply “Selection Only”, and “-Y Forward” and “Z Up”8 . Verify the new model loads correctly, e.g. in Meshlab9 ! 14.4.5 Beyond 3D: Temporally evolving Models Stellarium working as “time machine” can display the sky for any calendar date in its range of valid dates. Also landscapes and human-built structures evolve. Temples are being rebuilt, changed, re-dedicated or repurposed, new windows are cut, old windows closed. To show landscape and buildings in the right shape for the time in question, we can make material transparent, so that parts of the model are not displayed. To allow for archaeological uncertainties in dating construction and destruction, we can gradually fade in and fade out the model parts in question (Zotti, Schaukowitsch, and Wimmer, To Appear 2018). To enable this magic, you must combine all your models into one (see section 14.4.4), export as one OBJ/MTL as usual, and manually edit the MTL file. It is wise to give the material for the parts in question a reasonable name that you can later identify in the MTL file. Then you simply add one or both of the new keywords vis_fadeIn or vis_fadeOut to the material description, with 2 arguments which are the Julian days of begin and end of a phase transition. For sharp transitions, just use the same JD dates. # Some structure has been put up around -3100/ -3000 vis_fadeIn 588783.5 625308.5 # Fade away between 500 AD /700 AD vis_fadeOut 1903682.5 1976732.5 14.4.6 Working with non-georeferenced OBJ files There exists modeling software which produces nice models, but without concept of georeference. One spectacular example is AutoDesk PhotoFly, a cloud application which delivers 3D models from a bunch of photos uploaded via its program interface. This “technological preview” is in version 2 and free of cost as of mid-2011. The problem with these models is that you cannot assign surveyed coordinates to points in the model, so either you can georeference the models in other applications, or you must find the 8 9 0.16.1 154 Chapter 14. Scenery3d – 3D Landscapes correct transformation matrix. Importing the OBJ in Sketchup may take a long time for detailed photo-generated models, and the texturing may suffer, so you can cut the model down to the minimum necessary e.g. in Meshlab, and import just a stub required to georeference the model in Sketchup. Now, how would you find the proper orientation? The easiest chance would be with a structure visible in the photo layer of Google Earth. So, start a new model and immediately add location from the Google Earth interface. Then you can import the OBJ with TIG’s importer plugin. If the imported model looks perfect, you may just place the model into the Sketchup landscape and export a complete landscape just like above. If not, or if you had to cut/simplify the OBJ to be able to import it, you can rotate/scale the OBJ (it must be grouped!). If you see a shadow in the photos, you may want to set the date/time of the original photos in the scene and verify that the shadows created by Sketchup illuminating the model match those in the model’s photo texture. When you are satisfied with placement/orientation, you create a scenery3d.ini like above with the command Plugins ASTROSIM/Stellarium scenery3d helpers Create scenery3d.ini . Then, you select the OBJ group, open the Windows Ruby Console and readout data by calling Plugins ASTROSIM/Stellarium scenery3d helpers Export transformation of selected group . On the Ruby console, you will find a line of numbers (the 4 × 4 transformation matrix) which you copy/paste (all in one line!) into the [model] section in scenery3d.ini. obj2grid_trafo = < a11 > , < a12 > , < a13 > , < a14 > , < a21 > , < a22 > , < a23 > , < a24 > , , < a32 > , < a33 > , < a34 > , < a41 > , < a42 > , < a43 > , < a44 > You edit the scenery3d.ini to use your full (unmodified) PhotoFly model and, if you don’t have a panorama, take Zero Horizon landscape as (no-)background. It depends on the model if you want to be able to step on it, or to declare ground=NULL for a constant-height ground. Run Stellarum once and adjust the start_N, start_E and zero_ground_height. 14.4.7 Rotating OBJs with recognized survey points If you have survey points measured in a survey grid plus an image-based model with those points visible, you can use Meshlab to find the model vertex coordinates in the photo model, and some other program like CoordTrans in the JavaGraticule3D suite to find either the matrix values to enter in scenery3d.ini or even rotate the OBJ points. However, this involves more math than can be described here; if you came that far, you likely know the required steps. Here it really helps if you know how to operate automatic text processors like AWK. 14.5 Predefined views You can also configure and distribute some predefined views with your model in a viewpoints.ini file. The viewpoints can be loaded and stored with the viewpoint dialog which you can call with the button. See the provided “Sterngarten” scene for an example. These entries are not editable by the user through the interface. The user can always save his own views, they will be saved into the file userviews.ini in the user’s Stellarium user directory, and are editable. [ StoredViews ] size = < int > Defines how many entries are in this file . Prefix each entry with its index ! 1/ label = < string > The name of this entry 1/ description = < string > A description of this entry ( can include HTML ) 1/ position = The x ,y , z grid coordinates ( like orig_ * or start_ * in scenery3d . ini ) + the current eye height h 1/ view_fov = < az_deg , alt_deg , fov_deg > The view direction + FOV ( like s t a r t _ a z _ a l t _ f o v in scenery3d . ini ) 14.6 Example 155 ; an example for a second entry ( note the 2 at the beginning of each line !) 2/ label = Signs 2/ description = Two signs that describe the Sterngarten 2/ position = 593155.2421 ,5333348.6304 ,325.7295809038 ,0.8805 2/ view_fov = 84.315399 , -8.187078 ,83.000000 14.6 Example Let us add a quick example here. A recent paper (Pollard, 2017) claims that the Uffington White Horse, a geoglyph carved into a hillsite in England during the Bronze Age, may depict the mythical “Sun Horse”, a common conception of that period. Unfortunately, as of 2017, the official UK Lidar repository does not include the Uffington area, so a detailed GIS-based model is not available. We could use EUdem25 data with aerial imagery, or for a quick look, we just use Sketchup. Yet another unfortunate development: Trimble declared that after the 5-year transition period from Google to Trimble is over in May 2017, terrain modelling will be limited to Sketchup Pro. But note that a fresh installation comes with a 30-day Pro trial time, this should be enough for this example. First, locate the site in Google Earth at λ = −1.56718, ϕ = 51.582843. (Or just search for “Uffington”.) Try to identify which parts of the landscape may be visible from your site, so you can estimate which parts of terrain should be included in the model. Open Sketchup, select the meter-based “Landscape Architecture” template, add View Toolbars. . . : Locations. Click on the “Add Location” button of that toolbar. Enter “Uffington” into the location search dialog. This brings you close to our site of interest. Clip a part of terrain to import it to Sketchup. Optionally, add more terrain. If installed, TIG’s OBJ exporter is available from the File menu, or you can use Sketchup Pro’s built-in OBJ export. Export UffingtonHorse.obj to a subdirectory scenery3d/Uffington in your Stellarium user data directory. The geolocation is stored in an “AttributeDictionary”. To read this, press Window Ruby Console to open the Ruby Console. Then write a few lines of Ruby to get access to the Georeference dictionary and other data: model = Sketchup . active_model attrdicts = model . attribute_dictionaries attrdicts . each {| d | puts " AttributeDictionary : ␣ % s " % d . name d . each_pair { |k , v | puts " ␣ ␣ % s =% s " % [k , v ] } } model . shadow_info . each {| k , v | puts " ␣ #{ k } ␣ #{ v } " } utm = model . point_to_utm Geom :: Point3d . new (0 ,0 ,0) puts ( " grid_name = UTM ␣ % i ␣ % s ␣ (% s ) " % [ utm . zone_number , utm . zone_letter , model . get_datum ]) Note the ModelTranslation values. Those are inches (of all units!) in the UTM reference frame and define the model coordinate origin in world coordinates. (Actually, it uses the negative values.) Multiplication by 2.54 gives cm, and by 0.0254, meters in the UTM coordinate system. We will use the negatives of these values as orig_E, orig_N, orig_H. Additionally, we have found information about meridian convergence correction (Sketchup’s NorthAngle), UTM zone number etc. All this goes into our configuration file. Create this file scenery3d.ini with the content seen in fig. 14.1 156 Chapter 14. Scenery3d – 3D Landscapes [ model ] name = UffingtonHorse ; Either a fitting landscape or just ’ Zero Horizon ’: landscape = Zero Horizon scenery = UffingtonHorse . obj ; activate the next line if you have a separate ground layer ; ground = UffingtonHorse_ground . obj ; If model Y - axis points up , activate the next line ; obj_order = XZY author = Georg Zotti copyright =( c ) 2017 Georg Zotti description = Uffington Horse may represent the Sun Horse . \ See Joshua Pollard in Antiquity 91 356(2017): 406 -20. [ location ] name = UffingtonHorse country = UK planetName = Earth ; Set the following to a fitting landscape landscapeKey = Zero Horizon longitude = -1.56718254089355 latitude =51.5828432749823 altitude =137 [ coord ] grid_name = UTM 30 U ( WGS 84) gridType = UTM orig_E =599273.02119578 orig_N =5715615.15079106 orig_H =136.295297626736 convergence_angle =1.12284363771988 ; Height used outside the terrain , to not " fall ␣ off " the rim . zero_ground_height =137 ; You may want to reset these coordinates . ; Observer is set to those on loading the scenery . start_E =599273.02119578 start_N =5715615.15079106 start_az_alt_fov =50 ,10 ,83 Figure 14.1: scenery3d.ini for the Uffington example. 14.6 Example 157 Authors and Acknowledgements Scenery3d was conceived by Georg Zotti for the ASTROSIM10 project. A first prototype was implemented in 2010/2011 by Simon Parzer and Peter Neubauer as student work supervised by Michael Wimmer (TU Wien). Models for accuracy tests (Sterngarten, Testscene), and later improvements in integration, user interaction, .ini option handling, OBJ/MTL loader bugfixes and georeference testing by Georg Zotti. Andrei Borza in 2011/12 further improved rendering quality (shadow mapping, normal mapping) and speed (Zotti, 2015; Zotti and Neubauer, 2012a; Zotti and Neubauer, 2012b). In 2014–17, Florian Schaukowitsch adapted the code to work with Qt 5 and the Stellarium 0.13 codebase, replaced the renderer with a more efficient, fully shader-based system, implemented various performance, quality and usability enhancements, and did some code cleanup. Both Andrei and Florian were again supervised by Michael Wimmer (Zotti, 2016a; Zotti, 2016b; Zotti, Schaukowitsch, and Wimmer, To Appear 2018). This work has been originally created during the ASTROSIM project supported 2008-2012 by the Austrian Science Fund (FWF) under grant number P 21208-G19. 10 15. Stellarium at the Telescope Stellarium is great for indoor use on the desktop, but it is also very useful outdoors under the real sky, and several plugins enhance its usability particularly for observers. Two plugins are bundled with Stellarium which are designed to be used at the telescope: Oculars (section 15.1), which provides field of view hints for telescopes, oculars and sensors, and TelescopeControl (section 15.2), which allows you to send GOTO commands to many motorized telescope mounts. Other GOTO telescopes are supported by external programs which you must install separately: StellariumScope (section 15.5), RTS2 (section 15.3) or INDI (section 15.4). This can also help DIY hardware tinkerers who like to build their own control systems (section 15.6). In addition, the Observability plugin (section 15.7) can be used for planning the best times to observe your favourite objects. 15.1 Oculars Plugin T IMOTHY R EAVES , WITH ADDITIONS BY A LEXANDER W OLF This plugin serves several purposes: • to see what the sky looks like through a particular combination of eyepiece, lense (Barlow or Shapley types) and telescope. This plugin helps to get an idea of what you should see when looking through a physical telescope, and understand why one eyepiece may be better suited to observe a particular target than another. This can also be very useful for deciding what telescope is best suited to a style of viewing. And with the support for binoculars, you also have the ability to understand just about any type of optics-enhanced visual observing. • to show what a particular combination of camera and lens or telescope would be able to photograph of the sky. • lastly, with the help of the Telrad sight, understand where object in the sky are in relation to each other. This can be helpful for star-hopping with a non-GOTO telescope. None of these activities can take the place of hands-on experience, but they are a good way to supplement your visual astronomy interests. Chapter 15. Stellarium at the Telescope 160 Figure 15.1: The on-screen menu (top right) and popup menu (lower right) of the Oculars plugin. 15.1.1 Using the Ocular plugin The plugin is controlled through a popup menu or through an on-screen control panel (see top right corner on screens in fig. 15.17). By default, the hot key to display the popup is Alt + O ( Option + O for Mac users). This can be changed in the Editing Keyboard Shortcuts window (see section 4.7.1). The menu will popup where your cursor is located. The options available in the popup menu depend on what you are currently doing. In the default menu, you can choose to configure the plugin, activate a CCD, or activate the Telrad finder (see fig. 15.1). The menu is navigated by either the arrow keys on your keyboard or by your mouse. The and arrow keys move the selection up or down the menu, and the and arrow keys display or hide sub-menus. activates an option. Telrad Finder The Telrad view can be used without defining any of the items below. As a reflex sight is nonmagnifying, this feature can only be enabled when no eyepiece is selected. You still may want to zoom in a bit to better see which stars are in the circles (fig. 15.2). The three circles that appear in the center of the screen are 0.5◦ , 2.0◦ , and 4.0◦ in diameter. They stay centered in the screen, so move the “telescope” (click-drag the background) to center the circles on the object of interest. While the Telrad finder is active, you can not activate a CCD with the popup menu, but only with the on-screen menu. Figure 15.2: The left image is the default 60◦ , and the right one is 40◦ . 15.1 Oculars Plugin 161 CCD Sensors Figure 15.3: View of M37 through a CCD sensor of the Oculars plugin. Figure 15.4: View of M37 through a CCD sensor of the Oculars plugin (without on-screen control panel). This is a great way to get an idea of what a particular camera will be able to capture when attached to a particular telescope or lens. For using camera lenses, you must describe them as telescope with the appropriate values for the lens. When active, this feature will display a red bounding box of the area that will be captured, as well as zoom in to give a better view of the surroundings. You can manually zoom in or out from there. The default CCD view will appear similar to fig. 15.3 or, when you are working without the on-screen control panel, the information area in the upper right hand corner also shows angular size captured by the CCD (see fig. 15.4). When a CCD view is displayed, the popup menu changes as seen in fig. 15.5. You can select what telescope to use, as well as progress to the previous or next CCD, or go to a specific CCD. You can also rotate the CCD to better frame your subject, or to see if the CCD can be rotated in such a way as to catch your area of interest (see fig. 15.6). Once rotated, the CCD frame on screen displays the new orientation (see fig. 15.7). 162 Chapter 15. Stellarium at the Telescope Figure 15.5: The CCD sensor popup menu of the Oculars plugin. Figure 15.6: Setting rotation of CCD sensor in the popup menu. Figure 15.7: A rotated CCD sensor frame of the Oculars plugin. 15.1 Oculars Plugin 163 Oculars • Define some eyepieces and telescope (see section 15.1.2). • Select an object to view (i.e. a star, planet, etc.) + O for • Click the toolbar button for toggling the Ocular view, or press Ctrl + O ( Mac users). • Swap between eye pieces and telescopes to see how the view changes. This is really the area of interest to most telescopic observers. It is a great way to compare different eyepiece/telescope combinations, to see how they change the view of the sky. And it is easy to do so with binoculars too. To show this, let us use the M37 cluster as target. Through a pair of Celestron 15x70 binoculars, it would look like in fig. 15.8. Figure 15.8: The M37 cluster through a Celestron 15x70 binocular. A very pretty sight. Now, what would it look like through a Celestron 80 mm EDF finder ’scope, with an Explore Scientific 14 mm 100◦ eyepiece? See fig. 15.9! Figure 15.9: The M37 cluster through a Celestron 80 mm EDF with Explore Scientific 14 mm eyepiece. Not bad at all. But we like to see more! So we move the eyepiece to a C1400. See fig. 15.10 for the resulting view. 164 Chapter 15. Stellarium at the Telescope Figure 15.10: The M37 cluster through a Celestron C1400 with Tele Vue Nagler 31 mm eyepiece. Very nice indeed! So for this target, the C1400 is going to be the best bet. However, if my target was the Pleiades, the C1400 with that eyepiece would not be good – the 80EDF would do much better! When an eyepiece is active, the popup menu again changes. With a non-binocular eyepiece selected, you also have the ability to select a particular eyepiece or telescope. When a binocular is active, you can not select a telescope, as it is not relevant. Changing the eyepiece to a non-binocular will again allow the telescope to be selected. Also notice that when your mouse cursor is very near the right hand border of the screen, the popup menu’s sub-menus display to the left, not the right. 0.16.0 Star Scales As you know from section 4.4.1, the number and relative size of stars of various magnitudes can be adjusted to your personal preferences in the view settings window to approximate the appearance of the stars as seen by the naked eye. Some observers prefer to have a simulated ocular view with very small, or more, stars, quite different from what Stellarium usually shows. The Oculars plugin therefore keeps two additional sets of scaling values for ocular views and CCD views, which are activated automatically when you switch to ocular or CCD view, and which are stored immediately and permanently in the plugin’s ocular.ini file.1 15.1.2 Configuration All configuration is done through the user interface in the application. To open the configuration dialog hit the Alt + O key, or click the configure button on the plugin setup dialog (available in the Plugins tab of Stellarium’s Configuration window (opened by pressing F2 or the button in the left toolbar)), or the rightmost button of the on-screen panel (if displayed in the top right corner of screen). There are six tabs in the configuration dialog: General, Eyepieces, Lenses, Sensors, Telescopes, and About. The first five are the ones we are interested in here. 1 The appearance of stars may depend on various other factors: telescope type, ocular type, quality of optics, seeing, . . . Such details with all combinations cannot meaningfully be stored, though. These values should allow a rapid toggle on any single night. 15.1 Oculars Plugin 165 General The first option allows you to define the general behaviour of the plugin. The options are grouped by areas of usage: Interface, Ocular view and Sensor view (see figure 15.11). Figure 15.11: General tab of the Oculars plugin configuration dialog. Interface: this group of options allows to change behaviour of the plugin in general. On-screen control panel: show an additional GUI panel in the top-right corner of the screen to allow switching features of the plugin (in addition to the popup window). Restore FOV to initial values and Restore direction to initial values options allow restoration field of view and direction of view, resp., to the initial values at program start at the end of the plugin usage (e.g., when disabling the view through CCD frame). Show resolution criteria compute and show Rayleigh criterion, Dawes’, Abbe’s and Sparrow’s limits for combination of telescope, lens and eyepiece. In addition, this option will show visual resolution for selected “setup”. This option may be very helpful for double star observers. Arrow button scale allows to change the size of the arrow buttons in the ocular GUI panel. Ocular view is a group of options that allows to change the plugin’s behaviour in visual observation mode. Enable only if an object is selected – uncheck this option if you want to use the visual observation mode when no object is selected. Limit stellar magnitude allows to hide faint stars, which are invisible for the selected combination of eyepiece, lens and telescope. Hide grids and lines when enabled allows to hide grids and lines when you observe the sky through the eyepiece and re-enables their visibility when leaving visual observation mode. Scale image circle option allows you to define whether or not to scale the images based on apparent FOV. When deactivated, the image circle will fill your screen. In general, we recommend you not select this, unless you have a need to, because it can really 166 Chapter 15. Stellarium at the Telescope reduce the image size on the screen. It can however be very useful in comparing two eyepieces. If you set this option, the on-screen image will be scaled based on the eyepieces and telescopes you define. See section 15.1.3 for information on what scaling means, and why you might want to use it. Use semi-transparent mask: uncheck this option if you want to see visible field of view as in real telescope. Sensor view is group of options allows to change behaviour of the plugin for photographic observations mode. Use degrees and minutes for FOV of CCD – for many cases the use of decimal degrees for the value of the field of view is not comfortable, and this option allows to use the more human readable format for FOV. Enable automatic switch of mount type allows to store the CCD frame orientation when the type of telescope mount is changed. Eyepieces This is the tab used to enter your own eyepieces (see figures 15.12 and 15.13). By default, a few sample ones have been added; feel free to delete those once you’ve entered your own. The fields on this tab are: Name – a free-text description of the eye piece. You could modify this to match your personal descriptions of eyepieces. aFOV – apparent field of view in degrees. Focal Length – eyepiece focal length in mm. Field Stop – the field stop of the eyepiece in mm. This is used to calculate the true field of view of an eyepiece. If you do not know what it is just leave it the default zero. Not all manufacturers provide this value; TeleVue is one that does. Binoculars – selecting this checkbox tells the system that this eyepiece is binoculars or finders; this means that this eyepiece can be used without defining a telescope. Has permanent cross-hairs – selecting this checkbox tells the system that this eyepiece or binocular (finder) has also simple cross-hairs2 . When Binoculars are described, the relevant fields change to tFOV – true field of view in degrees. Magnification factor – the magnification of the binocular. Diameter – the diameter of the binocular objective in mm. Lenses This is the tab used to enter your own lenses (see figure 15.14). By default, a few sample ones have been added; feel free to delete them once you’ve entered your own. The fields on this tab are: Name – a free-text description of the lense. You could modify this to match your personal descriptions of lenses. Multiplier – a factor larger than 1 expands the focal length, and lenses with this type are named Barlow lense; a factor less than 1 reduces the focal length, and lenses with this type are named Shapley lense or focus reducer. Sensors This tab allows you to define sensors for any camera you may have (see figure 15.15). When defined and selected, this will draw a red bounding rectangle in the center of the eye piece view, showing 2 The Oculars plugin supports eyepieces with reticle patterns – both special eyepieces are available in the default list of eyepieces, and the option Has permanent cross-hairs is not related to those eyepieces. 15.1 Oculars Plugin 167 Figure 15.12: Eyepieces tab of Oculars plugin configuration dialog. Figure 15.13: Eyepieces tab of Oculars plugin configuration dialog (settings for binocular). 168 Chapter 15. Stellarium at the Telescope Figure 15.14: Lenses tab of Oculars plugin configuration dialog. what the CCD will capture. Because of the way floating point numbers are stored, sometimes you may see one of your defined values change (for example from 2.2 to 2.19999) but this should not affect what you see. Figure 15.15: Sensors tab of Oculars plugin configuration dialog. The fields on this tab are: Name – A free-text description of the sensor. Resolution x – the width of the sensor in pixels. Resolution y – the height of the sensor in pixels. Chip width – the width of the sensor in mm. Chip height – the height of the sensor in mm. Pixel width – the width of an individual pixel, in µm. Pixel height – the height of an individual pixel, in µm. Rotation Angle – the rotation angle of the sensor, in degrees. Binning x – the binning factor for the width of the sensor. Binning y – the binning factor for the height of the sensor. Off-Axis guider – selecting this checkbox tells the system that this sensor has support an off-axis guider also. 15.1 Oculars Plugin 169 Prism/CCD distance – distance between center of prism/CCD of Off-Axis Guider and optical axis of telescope in mm. Prism/CCD width – the width of the prism/CCD of Off-Axis Guider in mm. Prism/CCD height – the height of the prism/CCD of Off-Axis Guider in mm. Position Angle – the position angle of the prism/CCD of Off-Axis Guider, in degrees. The resolution is easy to find: these are simply the image dimensions of a (non-binned) frame. The chip size and pixel size may be more difficult, but the manual, or searching the Internet, should turn up these values. For a “full-frame” DSLR, this should be close to 36x24 mm, while APS-C should be around 22.5x15 mm. Pixel size is simply image size divided by resolution. Some cameras may have unsquare pixels. Telescopes This is the tab used to enter your own telescopes (see fig. 15.16). The fields on this tab are: Figure 15.16: Telescopes tab of Oculars plugin configuration dialog. Name – A free-text description of the telescope. Focal Length – telescope focal length in mm. Diameter – telescope diameter (aperture) in mm. Horizontal flip – if the view through this telescope should flip horizontally. Vertical flip – if the view through this telescope should flip vertically. Equatorial Mount – select it if this telescope has an equatorial mount. 15.1.3 Scaling the eyepiece view I (TR) would like to thank Al Nagler over at TeleVue3 for helping to set me straight on the topic of eyepieces. They are a lot more complicated than you might think! By default, the view drawn on your computer screen when the plugin is active fills the screen. That is, there is a circle drawn to represent the view through the eyepiece, and this circle will fill the screen. For general use, this is what most people would want. There will be times that it’s not. If you are going to be observing any deep space object, it can be very important to choose the best eyepiece for that object. You will typically want an eyepiece that will magnify the object as much as possible, while showing all of the object in the eyepiece view. Getting this can be tricky, especially if you do not like changing eyepieces at the telescope. Or maybe you want to understand why one type of telescope may be better than another type for observing what you are interested in. This is where you will want to scale the image on screen based on your eyepiece. Different eyepieces generally have a different apparent field of view (aFOV). An easy way to think about this is: the larger the aFOV, the bigger the picture you see in the eyepiece. Older types of eyepiece (some types still built and in wide use today have been constructed in the 19th 3 170 Chapter 15. Stellarium at the Telescope century) generally have their aFOV in the 50◦ range. Today, there are massive eyepieces available with 82◦ , and recently even 100◦ aFOV! These eyepieces are huge, as they require a lot of very special glass to achieve their incredible fields of view. An eyepiece of the same focal length with a 100◦ aFOV will produce an image through the eyepiece that is twice as wide as one produced by a 50◦ eyepiece. Different telescopes, with an eyepiece of a given aFOV, will also produce a different true field of view. This is the actual size of the piece of sky that you see through the eyepiece. Getting these two “just right” can be very important. It’s easy to assume that you want the biggest telescope you can get, with the eyepiece that gives you the highest magnification. This is never true in reality. Depending on where you live, and especially what you like to look at, a 100-120 mm quality refractor with a wide aFOV eyepiece may very well be better than a large SCT with the same eyepiece. This is something I learned the hard way. So how does scaling the eyepiece view help? The plugin will find the eyepiece you have with the largest aFOV. This aFOV becomes 100% of the computer screen diameter. Then, any other eyepiece will have its aFOV compared, and the view on screen will be scaled down accordingly. These 100◦ aFOV eyepieces makes the math here easy. If you have one, then when that eyepiece is used, the circle that represents the view through the eyepiece will take up 100% of the screen diameter. Next, if you select an eyepiece with an 82◦ aFOV, its view will be scaled to 82% of the screen, and a 62◦ aFOV eyepiece will be scaled to 62% of the screen. Example in action This is easier to understand in action, so let us look at an example that uses three eyepieces all with the same 17 mm focal length, so they all produce the same level of magnification (well, one has an 17.3 mm focal length, but its magnification is nearly identical) and see how the view changes. These example all use a Celestron C8 8" SCT telescope, and the target is the Great Orion Nebula. We can see from the images in fig. 15.17 that the target is all three images is the same size. The 100◦ image fills the screen, the 82◦ is smaller, and the 62◦ is smallest yet, filling 62% of the computer screen. Note that in each image, the field of view that you see changes. The larger the aFOV, the more you can see of the sky. So in this example, if you had an 8" telescope, you would want to use the 17 mm 100◦ Ethos eyepiece to see as much of the nebula as possible. 15.1 Oculars Plugin 171 Figure 15.17: Comparing apparent fields of view of (top) a 17 mm Tele Vue Ethos eyepiece with an aFOV of 100◦ . Magnification is 119.5×. (center) a 17 mm Tele Vue Nagler eyepiece with an aFOV of 82◦ . Magnification is 119.5×. (bottom) a 17.3 mm Tele Vue Delos eyepiece with an aFOV of 62◦ . Magnification is 117.5×. Chapter 15. Stellarium at the Telescope 172 15.2 TelescopeControl Plugin This plugin provides a simple control mechanism for motorised telescope mounts. The user selects an object (i.e. by clicking on something – a planet, a star etc.) and presses the telescope go-to key, and the telescope will be guided to the object. Multiple telescopes may be controlled simultaneously. WARNING Stellarium cannot prevent your telescope from being pointed at the Sun. It is up to you to ensure proper filtering and safety measures are applied! Never point your telescope at the Sun without a proper solar filter installed. The powerful light amplified by the telescope WILL cause irreversible damage to your eyes and/or your equipment. Even if you don’t do it deliberately, a slew during daylight hours may cause your telescope to point at the sun on its way to the given destination, so it is strongly recommended to avoid using the telescope control feature before sunset without appropriate protection. 15.2.1 Abilities and limitations This plug-in allows Stellarium to send only ’slew’ (’go to’) commands to the device and to receive its current position. It cannot issue any other commands, so users should be aware of the possibility for mount collisions and similar situations. (To abort a slew, you can start another one to a safe position.) Currently this plug-in does not allow satellite tracking unless the controlled telescope is an RTS2 system (see section 15.3), and is not very suitable for lunar or planetary observations. Many mounts can be set to a ’lunar’ tracking speed, you may prefer this. 15.2.2 Using this plug-in Here are two general ways to control a device with this plug-in, depending on the situation: DIRECT CONNECTION A device supported by the plug-in is connected with a cable to the computer running Stellarium INDIRECT CONNECTION local A device is connected to the same computer but it is driven by a stand-alone telescope server program or a third-party application that can ’talk’ to Stellarium; remote A device is connected to a remote computer and the software that drives it can ’talk’ to Stellarium over the network; this software can be either one of Stellarium’s stand-alone telescope servers, or a third party application. Most older telescopes use cables that connect to a serial port (RS-232), the newer ones use USB (Universal Serial Bus). On Linux and Max OS X, both cases are handled identically by the plug-in. On Windows, a USB connection may require a ’virtual serial port’ software, if it is not supplied with the cable or the telescope. Such a software creates a virtual (’fake’) COM port that corresponds to the real USB port so it can be used by the plug-in. On all three platforms, if the computer has no ’classic’ serial ports and the telescope can connect only to a serial port, a serial-to-USB (RS-232-to-USB) adapter may be necessary. Telescope set-up (setting geographical coordinates, performing alignment, etc.) should be done before connecting the telescope to Stellarium. 15.2.3 Main window (’Telescopes’) The plug-in’s main window can be opened: • By pressing the configure button for the plug-in in the Plugins tab of Stellarium’s Configuration window (opened by pressing F2 or the button in the left toolbar). 15.2 TelescopeControl Plugin 173 • By pressing the Configure telescopes... button in the Slew to window (opened by pressing Ctrl + 0 or the respective button on the bottom toolbar). The Telescopes tab displays a list of the telescope connections that have been set up: • The number (#) column shows the number used to control this telescope. For example, for telescope #2, the shortcut is Ctrl + 2 . • The Status column indicates if this connection is currently active or not. Unfortunately, there are some cases in which ’Connected’ is displayed when no working connection exists. • The Type field indicates what kind of connection this is: virtual means a virtual telescope (test mode). local, Stellarium means a DIRECT connection to the telescope (see above). local, external means an INDIRECT connection to a program running on the same computer. remote, unknown means an INDIRECT connection over a network to a remote machine. remote, RTS2 means an INDIRECT connection over a network to an RTS2 server. remote, INDI means an INDIRECT connection over a network to an INDI server. To set up a new telescope connection, press the Add button. To modify the configuration of an existing connection, select it in the list and press the Configure button. In both cases, a telescope connection configuration window will open. 15.2.4 Telescope configuration window Connection type The topmost field represents the choice between the types of connections (see section 15.2.2): Telescope controlled by: Stellarium, directly through a serial port is the DIRECT case External software or a remote computer is an INDIRECT case RTS2 Telescope is another INDIRECT case INDI is another INDIRECT case Nothing, just simulate one (a moving reticle) is a virtual telescope (no connection) Telescope properties Name is the label that will be displayed on the screen next to the telescope reticle. Connection delay If the movement of the telescope reticle on the screen is uneven, you can try increasing or decreasing this value. Coordinate system Some Celestron telescopes have had their firmware updated and now interpret the coordinates they receive as coordinates that use the equinox of the date (EOD, also known as JNow), making necessary this setting. Start/connect at startup Check this option if you want Stellarium to attempt to connect to the telescope immediately after it starts. Otherwise, to start the telescope, you need to open the main window, select that telescope and press the Start/Connect button. Device settings This section is active only for DIRECT connections (see above). Serial port sets the serial port used by the telescope. There is a pop-up box that suggests some default values: • On Windows, serial ports COM1 to COM10 • On Linux, serial ports /dev/ttyS0 to /dev/ttyS3 and USB ports /dev/ttyUSB0 to /dev/ttyUSB3. Make sure you have read/write access to the tty device. Depending on your flavour of Linux, this may e.g. require some group membership. • On Mac OS X, the list is empty as it names its ports in a peculiar way. If you are using v0.16.0 v0.17.0 Chapter 15. Stellarium at the Telescope 174 an USB cable, the default serial port of your telescope most probably is not in the list of suggestions. To list all valid serial port names in Mac OS X, open a terminal and type: ls / dev /* This will list all devices, the full name of your serial port should be somewhere in the list (for example, /dev/cu.usbserial-FTDFZVMK). Device model : see 15.2.5 Supported devices. Connection settings Both fields here refer to INDIRECT connections, which implies communication over a network (TCP/IP). Host can be either a host name or an IPv4 address such as ’’. The default value of ’localhost’ means ’this computer’. Modifying the default host name value makes sense only if you are attempting a remote connection over a network. In this case, it should be the name or IP address of the computer that runs a program that runs the telescope. Port refers to the TCP port used for communication. The default value depends on the telescope number and ranges between 10001 and 10009. v0.16.0 v0.17.0 RTS2 settings (see also 15.3) You will need access to an RTS2 HTTPD server through HTTP/JSON calls. Please see RTS2 documentation (man rts2-httpd) for details. You will as well need username and password for HTTPD. Please be aware that in order to move the telescope, your user must have the telescope in the list of allowed devices in the database. Please see man rts2-user for details on how to manipulate RTS2 users. URL points to RTS2 HTTPD. Can include anything a URL can have - port (:8889) and prefix path for RTS2 access. Username username used for login to RTS2 HTTPD. Password password for login to RTS2 HTTPD. INDI settings (see also 15.4) You will need access to an INDI server through a TCP/IP connection. Please see INDI documentation for details. You will need to select the correct INDI device to manage it. User Interface Settings: Field of view indicators A series of circles representing different fields of view can be added around the telescope marker. This is a relic from the times before the Oculars plug-in (see 15.1) existed. Activate the ’Use field of view indicators’ option, then enter a list of values separated with commas in the field below. The values are interpreted as degrees of arc. These marks can be used in combination with a virtual telescope to display a moving reticle with the Telrad circles. ’Slew telescope to’ window The Slew telescope to window can be opened by pressing Ctrl + 0 or the respective button in the bottom toolbar. It contains two fields for entering celestial coordinates, selectors for the preferred format (Hours-Minutes-Seconds, Degrees-Minutes-Seconds, or Decimal degrees), a drop-down list and two buttons. The drop-down list contains the names of the currently connected devices. If no devices are connected, it will remain empty, and the Slew button will be disabled. 15.2 TelescopeControl Plugin 175 Pressing the Slew button slews the selected device to the selected set of coordinates. See the section about keyboard commands below for other ways of controlling the device. Pressing the Configure telescopes. . . button opens the main window of the plug-in. TIP: Inside the ’Slew’ window, underlined letters indicate that pressing Alt + underlined letter can be used instead of clicking. For example, pressing Alt + S is equivalent to clicking the Slew button, pressing Alt + E switches to decimal degree format, etc. Sending commands Once a telescope is successfully started/connected, Stellarium displays a telescope reticle labelled with the telescope’s name on its current position in the sky. The reticle is an object like every other in Stellarium - it can be selected with the mouse, it can be tracked and it appears as an object in the ’Search’ window. To point a device to an object: Select an object (e.g. a star) and press the number of the device while holding down the Ctrl key. (For example, Ctrl + 1 for telescope #1.) This will move the telescope to the selected object. Note that most telescopes can only execute a single command to move to that object’s position, but if the telescope is an RTS2 telescope, you can even track a satellite (if the mount then is fast enough to support it).4 To point a device to the center of the view: Press the number of the device while holding down the Alt key. (For example, Alt + 1 for telescope #1.) This will slew the device to the point in the center of the current view. (If you move the view after issuing the command, the target won’t change unless you issue another command.) To point a device to a given set of coordinates: Use the Slew to window (press Ctrl + 0 ). 15.2.5 Supported devices Directly connected telescopes All devices listed in the ’Device model’ list are convenience definitions using one of the two built-in interfaces: the Meade LX200 (the Meade Autostar controller) interface and the Celestron NexStar interface. The device list contains the following: Celestron NexStar (compatible) Any device using the NexStar interface. Losmandy G-11 A computerized telescope mount made by Losmandy (Meade LX-200/Autostar interface). Meade Autostar compatible Any device using the LX-200/Autostar interface. Meade ETX-70 (#494 Autostar, #506 CCS) The Meade ETX-70 telescope with the #494 Autostar controller and the #506 Connector Cable Set. According to the tester, it is a bit slow, so its default setting of ’Connection delay’ is 1.5 seconds instead of 0.5 seconds. Meade LX200 (compatible) Any device using the LX-200/Autostar interface. Sky-Watcher SynScan AZ mount The Sky-Watcher SynScan AZ GoTo mount is used in a number of telescopes. Sky-Watcher SynScan (version 3 or later) SynScan is also the name of the hand controller used in other Sky-Watcher GoTo mounts, and it seems that any mount that uses a SynScan controller version 3.0 or greater is supported by the plug-in, as it uses the NexStar protocol. Wildcard Innovations Argo Navis (Meade mode) Argo Navis is a ’Digital Telescope Computer’ by Wildcard Innovations. It is an advanced digital setting circle that turns an ordinary telescope (for example, a dobsonian) into a ’Push To” telescope (a telescope that uses a computer to find targets and human power to move the telescope itself). Just don’t forget to set it to Meade compatibility mode and set the baud rate to 9600B1. 4 Actually, the TLE orbital elements of the selected satellite are transmitted to RTS2, which does then compute the satellite position itself. 176 Chapter 15. Stellarium at the Telescope v0.16.0 RTS2 telescopes Setting up a robotic telescope and dome control system with RTS2 is beyond the scope of this handbook, but see section 15.3 for a few notes to be able to connect and command the telescope with Stellarium. Please refer to the RTS2 Web pages5 for further details. Please be aware that some RTS2 usernames might have only read-only access. If this is case for your username, the telescope marker will be painted red (or color_telescope_readonly from Stellarium’s settings file). v0.17.0 INDI telescopes Setting up a robotic telescope and dome control system with INDI is beyond the scope of this handbook, but see section 15.4 for a few notes to be able to connect and command the telescope with Stellarium. Please refer to the INDI web pages6 for further details. Virtual telescope If you want to test this plug-in without an actual device connected to the computer, choose “Nothing, just simulate one (a moving reticle)” in the Telescope controlled by: field. It will show a telescope reticle that will react in the same way as the reticle of a real telescope controlled by the plug-in. See the section above about field of view indicators for a possible practical application (emulating ’Telrad’ circles). 15.3 v0.16.0 RTS2 RTS2, the Remote Telescope System 2, is a complete robotic observatory control system for Linux by Petr Kubánek, who kindly provided the plugin code to make RTS2 interoperate with Stellarium. We cannot give a full manual or any further support for RTS2 here, please refer to its website7 for complete instructions about dome control, cameras, filter wheels, weather sensors, etc. A few notes may be useful for beginners, though. RTS2’s central piece is a daemon. Start the system: sudo service rts2 start RTS2’s main control screen is text-based, rts2-mon. For a quick check, switch on the system using F9 . Telescope T0 is a dummy telescope which you can select and operate with commands like move 120 35 (this moves to RA=120◦ =8h, DEC=35◦ , but only when this position is above your horizon). Stellarium’s Telescope plugin can communicate with RTS2 using the RTS2 web interface. You must run rts2-httpd for this, which may require the right permissions to write the lock files in /var/run. This program requires that a database has been created as described in the file RUN in RTS2’s source directory and on the RTS2 website8 . Also, you must create a ’user’ for RTS2. This is not a regular Linux account, but an entry in the RTS2 database. Create a user with rts2-user -a . You should use a password different from your regular Linux password, as this will be transmitted in plain text between the computer running Stellarium and the RTS2 control computer, and may also be written into Stellarium’s logfile. Then you can enable device control for the respective user. If you want to send slew commands from Stellarium, make sure to allow access to telescope T0. If not, Stellarium will be able to show the telescope marker, but you will not be able to control the telescope. To enable control for existing users in the default stars database, 5 6 7 8 15.4 INDI 177 psql stars update users set allowed_devices = ’* ’; In case you cannot properly connect to the RTS2 telescope or cannot send slew commands, check Stellarium’s logfile log.txt for some diagnostic messages. RTS2 is the only type of telescope supported by Stellarium which can autonomously track satellites. Tracking accuracy fully depends on Stellarium’s TLE satellite elements being up-to-date (see section 13.8) and the accuracy of your RTS2 installation. 15.4 INDI INDI, the Instrument Neutral Distributed Interface, is a distributed control system (DCS) protocol to enable control, data acquisition and exchange among hardware devices and software front ends, emphasizing astronomical instrumentation9 . INDI client (v1.6.0) has been incorporated into Stellarium’s Telescope Control plugin by Alessandro Siniscalchi to allow Stellarium to communicate with INDI hardware drivers via INDI server. INDI server is a hub that sits between drivers and clients. It reroutes traffic for control and data across distributed networks. Each device or client in the network is a node and may communicate with other nodes whenever desired. The server supports broadcasting, chaining, and marshalling of data. Stellarium only supports INDI mounts (no other INDI devices), and you will need to select the correct INDI device to manage it at the stage of configuration of telescope. For this purpose the plug-in has a tool to getting the list of connected devices from the INDI server (when the server is working!). Please define hostname and port10 in the “INDI Settings” block, press Refresh devices and select the required device in the list “Devices”. List of telescope types supported by INDI11 : • Meade Autostar • Meade LX200 (Classic/GPS/16) • Celestron NexStar • Celestron NexStar Evolution • Orion Synscan Telescope • EQ-6 MCU Update • HEQ-5 MCU Update • LittleFoot Vpower • LittleFoot Elegance Photo • Astro-Electronic FS-2 • EQMod • Pulsar2 • SkySensor2000PC • Takahashi Temma • 10 Micron • Losmandy Gemini • Astrophysics • Skywatcher Virtuoso (Alt/Az) • IOptron IEQPro/CEM60 9 10 The Internet Assigned Numbers Authority (IANA) has assigned to INDI the Transmission Control Protocol and User Datagram Protocol (TCP/UDP) port 7624. 11 v0.17.0 Chapter 15. Stellarium at the Telescope 178 • IOptron ZEQ25/SmartEQ • IOptron GotoNova Upgrade Kit 8400 15.5 StellariumScope StellariumScope is a free add-on that enables you to control your telescope with Stellarium. Features • Provides an interface between Stellarium and ASCOM telescope drivers. • Provides the ability to both “Sync” and “Slew” the telescope. It’s also possible to issue a stop/cancel command from Stellarium. • You can easily host Stellarium on one computer linked to another control computer that hosts the telescope driver. • The installation program will automatically install the documentation, but the link to the documentation is provided by developer12 so you can read it before installation. • There are earlier releases still available on the downloads page on Welsh Dragon Computing site. The original StellariumScope program was designed and implemented by Scott of ByteArts and is still available for download13 . If you have difficulties with the releases available on the Welsh Dragon Computing site14 , you may want to consider using the original version. Figure 15.18 shows the interface and some of the options. Use this application (like all software that controls your mount) with supervision of your mount’s movements. 15.6 Other telescope servers and Stellarium Other developers have also been busy creating hard- and software often involving Arduino or Raspberry Pi boards which can control GOTO or PUSHTO (manually driven but position-aware, usually Dobsonian) telescopes and are ultimately controlled from Stellarium. Those are not related nor authored by the Stellarium team, so while we welcome such development (esp. open-sourced) in general, we cannot provide documentation nor any support. A few examples: iTelescope node-telescope-server One anonymous user sent a troubleshooting solution when connecting Stellarium to the Celestron NexRemote software: One tricky Window XP issue I fixed was that my older laptop would transiently lose connection with Stellarium although the status would still be “Connected” and all looked normal. [. . . ] I boosted the NexRemote.exe process in Windows XP to High under Set Priority under the Windows Task Manager via Ctrl + Alt + Del . All slews now proceed normally. Problem went away.15 12 StellariumScope User’s Guide — stellariumscope_user_guide.2015.10.24.pdf 13 14 about-stellariumscope 15 ?limit=25#8ffa 15.6 Other telescope servers and Stellarium Figure 15.18: StellariumScope interface 179 180 15.7 Chapter 15. Stellarium at the Telescope Observability Plugin This Plugin is activated with the button . It analyzes the observability of the selected object (or the screen center, if no object is selected). The plugin can show rise, transit, and set times, as well as the best epoch of the year (i.e., largest angular separation from the Sun), the date range when the source is above the horizon at dark night, and the dates of Acronychal and Cosmical rise/set. Ephemerides of the Solar-System objects and parallax effects are taken into account. Explanation of some parameters Sun altitude at twilight Any celestial object will be considered visible when the Sun is below this altitude. The altitude at astronomical twilight ranges usually between -12 and -18 degrees. This parameter is only used for the estimate of the range of observable epochs (see below). Horizon altitude Minimum observable altitude (due to mountains, buildings, or just a limited telescope mount). Today ephemeris Self-explanatory. The program will show the rise, set, and culmination (transit) times. The exact times for these ephemeris are given in two ways: as time spans (referred to the current time) and as clock hours (in local time). Acronychal/Cosmical/Heliacal rise/set The days of Cosmical rise/set of an object are estimated as the days when the object rises (or sets) together with the rise/set of the Sun. The exact dates of these ephemeris depend on the Observer’s location. On the contrary, the Acronycal rise (or set) happens when the star rises/sets with the setting/rising of the Sun (i.e., opposite to the Sun). On the one hand, it is obvious that the source is hardly observable (or not observable at all) in the dates between Cosmical set and Cosmical rise. On the other hand, the dates around the Acronychal set and rise are those when the altitude of the celestial object uses to be high when the Sun is well below the horizon (hence the object can be well observed). The date of Heliacal rise is the first day of the year when a star becomes visible. It happens when the star is close to the eastern horizon roughly before the end of the astronomical night (i.e., at the astronomical twilight). In the following nights, the star will be visibile during longer periods of time, until it reaches its Heliacal set (i.e., the last night of the year when the star is still visible). At the Heliacal set, the star sets roughly after the beginning of the astronomical night. Largest Sun separation Happens when the angular separation between the Sun and the celestial object are maximum. In most cases, this is equivalent to say that the Equatorial longitudes of the Sun and the object differ by 180 degrees, so the Sun is in opposition to the object. When an object is at its maximum possible angular separation from the Sun (no matter if it is a planet or a star), it culminates roughly at midnight, and on the darkest possible area of the Sky at that declination. Hence, that is the ’best’ night to observe a particular object. Nights with source above horizon The program computes the range of dates when the celestial object is above the horizon at least during one moment of the night. By ’night’, the program considers the time span when the Sun altitude is below that of the twilight (which can be set by the user; see above). When the objects are fixed on the sky (or are exterior planets), the range of observable epochs for the current year can have two possible forms: either a range from one date to another (e.g., 20 Jan to 15 Sep) or in two steps (from 1 Jan to a given date and from another date to 31 Dec). In the first case, the first date (20 Jan in our example) shall be close to the so-called ’Heliacal rise of a star’ and the second date (15 Sep in our example) shall be close to the ’Heliacal set’. In the second case (e.g., a range in the form 1 Jan to 20 May and 21 Sep to 31 Dec), the first date (20 May in our example) would be close to the Heliacal set and the second one (21 Sep in our example) to the Heliacal rise. More exact equations to estimate the Heliacal rise/set of stars and planets (which will not depend on the 15.7 Observability Plugin 181 mere input of a twilight Sun elevation by the user) will be implemented in future versions of this plugin. Full Moon When the Moon is selected, the program can compute the exact closest dates of the Moon’s opposition to the Sun. Note on Terminology The (sparse) literature on terminology about computing these Heliacal, Acronychal or Cosmic events seems to disagree on which end of the night is to be computed. While all agree about Heliacal rises taking place in the morning, Acronychal and Cosmic are sometimes applied in reverse order from those described here. In case you use these data, make sure you keep this definition as well. Author This plugin has been contributed by Ivan Marti-Vidal (Onsala Space Observatory)16 with some advice by Alexander Wolf and Georg Zotti. 16 16. Scripting 16.1 Introduction The development of a powerful scripting system has been continuing for a number of years now and can now be called operational. The use of a script was recognised as a perfect way of arranging a display of a sequence of astronomical events from the earliest versions of Stellarium and a simple system called Stratoscript was implemented. The scripting facility is Stellarium’s version of a Presentation, a feature that may be used to run an astronomical or other presentation for instruction or entertainment from within the Stellarium program. The original Stratoscript was quite limited in what it could do so a new Stellarium Scripting System has been developed. Since version 0.10.1, Stellarium has included a scripting feature based on the Qt Scripting Engine1 . This makes it possible to write small programs within Stellarium to produce automatic presentations, set up custom configurations, and to automate repetitive tasks. As of version 0.14.0 a new scripting engine has reached a level where it has all required features for usage, however new commands may be added from time to time. Since version 0.14.0 support of scripts for the Stratoscript engine has been discontinued. The programming language ECMAscript2 (also known as JavaScript) gives users access to all basic ECMAScript language features such as flow control, variables, string manipulation and so on. Interaction with Stellarium-specific features is done via a collection of objects which represent components of Stellarium itself. The various modules of Stellarium, and also activated plugins, can be called in scripts to calculate, move the scene, switch on and off display of objects, etc. You can write text output into text files with the output() command. You can call all public slots which are documented in the scripting API documentation3 . 1 2 3 184 16.2 Chapter 16. Scripting Script Console It is possible to open, edit run and save scripts using the script console window. To toggle the script console, press F12 . The script console also provides an output window in which script debugging output is visible. 16.3 Includes Stellarium provides a mechanism for splitting scripts into different files. Typical functions or lists of variables can be stored in separate .inc files and used within other scripts through the include() command: include ( " common_objects . inc " ); 16.4 Minimal Scripts This script prints “Hello Universe” in the Script Console log window and into log.txt: core . debug ( " Hello Universe " ); This script prints “Hello Universe” in the Script Console output window and into the file output.txt which you will also find in the user data directory. The absolute path to the file will also be given in log.txt. core . output ( " Hello Universe " ); The file output.txt will be rewritten on each run of Stellarium. In case you need to save a copy of the current output file to another file, call core . saveOutputAs ( " myImportantData . txt " ); core . resetOutput (); This script uses the LabelMgr module to display “Hello Universe” in red, fontsize 20, on the screen for 3 seconds. var label = LabelMgr . labelScreen ( " Hello Universe " , 200 , 200 , true , 20 , " # ff0000 " ); core . wait (3); LabelMgr . deleteLabel ( label ); 16.5 Example: Retrograde motion of Mars A good way begin writing of scripts: set yourself a specific goal and try to achieve it with the help of few simple steps. Any complex script can be split into simple parts or tasks, which may solve any newbie problems in scripting. Let me explain it with examples. Imagine that you have set a goal to make a demonstration of a very beautiful, but longish phenomenon — the retrograde motion of the planet Mars (Fig. 16.1). 16.5.1 Script header Any “complex” script should contain a few lines in the first part of the file, which contains important data for humans — the name of the script and its description — and some rules for Stellarium. You can even assign default shortcuts in the script header, but make sure you assign a key not used 16.5 Example: Retrograde motion of Mars 185 Figure 16.1: Retrograde motion of Mars in 2005. (Credit & Copyright: Tunc Tezel — APOD: 2006 April 22 – Z is for Mars.) elsewhere! The description may cover several lines (until the end of the commented header) and should therefore be the last entry of the header. // // // // // // // // 16.5.2 Name : Retrograde motion of Mars Author : John Doe License : Public Domain Version : 1.0 Shortcut : Ctrl + M Description : A demo of retrograde motion of Mars . A body of script At the first stage of writing of the script for a demo of retrograde motion of Mars we should set some limits for our demo. For example we want to see motion of Mars every day during 250 days since October 1st , 2009. Choosing a value of field of view and of the coordinates of the center of the screen should be done at the this stage also. Let’s add few lines of code into the script after the header and run it: core . setDate ( " 2009 -10 -01 T10 :00:00 " ); core . moveToRaDec ( " 08 h44m41s " , " +18 d09m13s " ,1); StelMovementMgr . zoomTo (40 , 1); for ( i =0; i < 250; i ++) { core . setDate ( " + 1 days " ); core . wait (0.2); 186 Chapter 16. Scripting } OK, Stellarium is doing something, but what exactly is it doing? The ground and atmosphere is enabled and any motion of Mars is invisible. Let’s add an another few lines into the script (hiding the landscape and atmosphere) after setting date and time: LandscapeMgr . setFlagLandscape ( false ); LandscapeMgr . setFlagAtmosphere ( false ); The whole sky is moving now — let’s lock it! Add this line after previous lines: StelMovementMgr . setFlagLockEquPos ( true ); It looks better now, but what about cardinal points, elements of GUI and some “glitch of movement”? Let’s change the script: core . setDate ( " 2009 -10 -01 T10 :00:00 " ); LandscapeMgr . setFlagCardinalsPoints ( false ); LandscapeMgr . setFlagLandscape ( false ); LandscapeMgr . setFlagAtmosphere ( false ); core . setGuiVisible ( false ); core . moveToRaDec ( " 08 h44m41s " , " +18 d09m13s " ,1); StelMovementMgr . setFlagLockEquPos ( true ); StelMovementMgr . zoomTo (40 , 1); core . wait (2); for ( i =0; i < 250; i ++) { core . setDate ( " + 1 days " ); core . wait (0.2); } core . setGuiVisible ( true ); It’s better, but let’s draw the “path” of Mars! Add those line before the loop: core . selectObjectByName ( " Mars " , false ); SolarSystem . setFlagIsolatedTrails ( true ); SolarSystem . setFlagTrails ( true ); Hmm. . . let’s add a few strings with info for users (insert those lines after the header): var color = " # ff9900 " ; var info = LabelMgr . labelScreen ( " A motion of Mars " , 20 , 20 , false , 24 , color ); var apx = LabelMgr . labelScreen ( " Setup best viewing angle , FOV and date / time . " , 20 , 50 , false , 18 , color ); LabelMgr . setLabelShow ( info , true ); LabelMgr . setLabelShow ( apx , true ); core . wait (2); LabelMgr . setLabelShow ( apx , false ); Let’s add some improvements to display info for users — change in the loop: var label = LabelMgr . labelObject ( " Normal motion , West to East " , " Mars " , true , 16 , color , " SE " ); for ( i =0; i < 250; i ++) { 16.6 More Examples 187 core . setDate ( " + 1 days " ); if (( i % 10) == 0) { var strDate = " Day " + i ; LabelMgr . setLabelShow ( apx , false ); var apx = LabelMgr . labelScreen ( strDate , 20 , 50 , false , 16 , color ); LabelMgr . setLabelShow ( apx , true ); } if ( i == 75) { LabelMgr . deleteLabel ( label ); label = LabelMgr . labelObject ( " Retrograde or opposite motion begins " , " Mars " , true , 16 , color , " SE " ); core . wait (2); LabelMgr . deleteLabel ( label ); label = LabelMgr . labelObject ( " Retrograde motion " , " Mars " , true , 16 , color , " SE " ); } if ( i == 160) { LabelMgr . deleteLabel ( label ); label = LabelMgr . labelObject ( " Normal motion returns " , " Mars " , true , 16 , color , " SE " ); core . wait (2); LabelMgr . deleteLabel ( label ); label = LabelMgr . labelObject ( " Normal motion " , " Mars " , true , 16 , color , " SE " ); } core . wait (0.2); } 16.6 More Examples The best source of examples is the scripts sub-directory of the main Stellarium source tree. This directory contains a sub-directory called tests which are not installed with Stellarium, but are nonetheless useful sources of example code for various scripting features. IV Practical Astronomy 17 Astronomical Concepts . . . . . . . . . . . . . . . . . 191 18 Astronomical Phenomena 19 A Little Sky Guide . . . . . . . . . . . . . . 207 . . . . . . . . . . . . . . . . . . . . . . . . 223 20 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 17. Astronomical Concepts BARRY G ERDES , WITH ADDITIONS BY G EORG Z OTTI This section includes some general notes on astronomy in an effort to outline some concepts that are helpful to understand features of Stellarium. Material here is only an overview, and the reader is encouraged to get hold of a couple of good books on the subject. A good place to start is a compact guide and ephemeris such as the National Audubon Society Field Guide to the Night Sky1 . Also recommended is a more complete textbook such as Universe. There are also some nice resources on the net, like the Wikibooks Astronomy book2 . 17.1 The Celestial Sphere The Celestial Sphere is a concept which helps us think about the positions of objects in the sky. Looking up at the sky, you might imagine that it is a huge dome or top half of a sphere, and the stars are points of light on that sphere. Visualising the sky in such a manner, it appears that the sphere moves, taking all the stars with it — it seems to rotate. Watching the movement of the stars we can see that they seem to rotate around a static point about once a day. Stellarium is the perfect tool to demonstrate this! 1. Open the location dialog ( F6 ). Set the location to be somewhere in mid-Northern latitudes. (Just click on the map to select a location, or fine-tune with the settings.) The United Kingdom is an ideal location for this demonstration. 2. Turn off atmospheric rendering A and ensure cardinal points are turned on ( Q ). This will keep the sky dark so the Sun doesn’t prevent us from seeing the motion of the stars when it is above the horizon. 3. Pan round to point North, and make sure the field of view is about 90◦ . 4. Pan up so the ‘N’ cardinal point on the horizon is at the bottom of the screen. 1 2 192 Chapter 17. Astronomical Concepts 5. Now increase the time rate. Press K , L , L , L , L – this should set the time rate so the stars can be seen to rotate around a point in the sky about once every ten seconds. If you watch Stellarium’s clock you’ll see this is the time it takes for one day to pass at this accelerated rate. The point which the stars appear to move around is one of the Celestial Poles. The apparent movement of the stars is due to the rotation of the Earth. Our location as the observer on the surface of the Earth affects how we perceive the motion of the stars. To an observer standing at Earth’s North Pole, the stars all seem to rotate around the zenith (the point directly upward). As the observer moves South towards the equator, the location of the celestial pole moves down towards the horizon. At the Earth’s equator, the North celestial pole appears to be on the Northern horizon. Similarly, observers in the Southern hemisphere see the Southern celestial pole at the zenith when they are at the South pole, and it moves to the horizon as the observer travels towards the equator. 1. Leave time moving on nice and fast, and open the configuration window. Go to the location tab and click on the map right at the top – i.e., set your location to the North pole. See how the stars rotate parallel to the horizon, around a point right at the top of the screen. With the field of view set to 90◦ and the horizon at the bottom of the screen, the top of the screen is the zenith. 2. Now click on the map again, this time a little further South. You should see the positions of the stars jump, and the centre of rotation has moved a little further down the screen. 3. Click on the map even further towards and equator. You should see the centre of rotation having moved down again. To help with the visualisation of the celestial sphere, turn on the equatorial grid by clicking the button on the main tool-bar or pressing the E key. Now you can see grid lines drawn on the sky. These lines are like lines of longitude and latitude on the Earth, but drawn for the celestial sphere. The Celestial Equator is the line around the celestial sphere that is half way between the celestial poles – just as the Earth’s equator is the line half way between the Earth’s poles. 17.2 Coordinate Systems 17.2.1 Altitude/Azimuth Coordinates The Horizontal Coordinate System (also called Altitude/Azimuth coordinate system) can be used to describe a direction of view (the azimuth angle) and an angular height in the sky (the altitude angle). The azimuth angle is measured clockwise round from due North3 . Hence North itself is 0◦ , East 90◦ , Southwest is 225◦ and so on. The altitude angle is measured up from the mathematical horizon, which is just halfway between “straight up” and “straight down”, without regard to the landscape. Looking directly up (at the zenith) would be 90◦ , half way between the zenith and the horizon is 45◦ and so on. The point opposite the zenith is called the nadir. The Altitude/Azimuth coordinate system is attractive in that it is intuitive – most people are familiar with azimuth angles from bearings in the context of navigation, and the altitude angle is something most people can visualise pretty easily. However, the altitude/azimuth coordinate system is not suitable for describing the general position of stars and other objects in the sky – the altitude and azimuth values for a celestial object change with time and the location of the observer. 3 In some textbooks azimuth is counted from south. There is no global authority to decide upon this issue, just be aware of this when you compare numbers with other sources. 17.2 Coordinate Systems 193 Figure 17.1: Altitude/Azimuth (Horizontal) Coordinate System Stellarium can draw grid lines for altitude/azimuth coordinates. Use the main tool-bar to activate this grid, or press the Z key. button on the In addition, the cardinal points can be highlighted using the button or Q key. There are a few great circles with special names which Stellarium can draw (see section 4.4.3). Meridian This is the vertical line which runs from the North point towards the zenith and further to the South point. (Mathematical) Horizon This is the line exactly 90◦ away from the zenith. First Vertical This is the vertical line which runs from the East point towards the zenith and further to the West point. 17.2.2 Right Ascension/Declination Coordinates Like the Altitude/Azimuth system, the Right Ascension/Declination (RA/Dec) Coordinate System (or Equatorial Coordinate System) uses two angles to describe positions in the sky. These angles 194 Chapter 17. Astronomical Concepts Figure 17.2: Equatorial Coordinates are measured from standard points on the celestial sphere. Right ascension α and declination δ are to the celestial sphere what longitude and latitude are to terrestrial map makers. The Northern celestial pole has a declination of δ = 90◦ , the celestial equator has a declination of δ = 0◦ , and the Southern celestial pole has a declination of δ = −90◦ . Right ascension is measured as an angle round from a point in the sky known as the First Point of Aries, in the same way that longitude is measured around the Earth from Greenwich. Figure 17.2 illustrates RA/Dec coordinates. The angle α is usually expressed as time with minute and seconds, with 15◦ equalling one hour. Unlike Altitude/Azimuth coordinates, RA/Dec coordinates of a star do not change if the observer changes latitude, and do not change noticeably over the course of the day due to the rotation of the Earth. RA/Dec coordinates are generally used nowadays in star catalogues such as the Hipparcos catalogue. However, the story is complicated a little by precession (section 17.8) and parallax (section 17.9). Precession causes a slow drift of the coordinates almost parallel to the ecliptic, and 17.2 Coordinate Systems 195 therefore star catalogues always have to specify their equinox of validity. Current catalogs and atlases use coordinates for J2000.0. Stellarium can draw grid lines for Equatorial coordinates. Use the button on the main tool-bar to activate this grid, or press the E key to draw the equatorial grid for the simulation time. The Markings dialog (4.4.3) allows you to set also the grid for J2000.0 standard coordinates. In case you are observing from another celestial object, the equatorial coordinates use a system similar to the one referring to the earth-based coordinates, but parallel to the planet’s rotational axis. There are again a few great circles with special names which Stellarium can draw in addition, both for simulation time and for J2000.0 (see section 4.4.3). Celestial Equator the line directly above the earth’s (or more generally, the observer’s planet’s) equator. Colures These are lines similar to meridian and first vertical in the azimuthal system. The Equinoctial Colure runs from the North Celestial Pole NCP through the First Point of Aries à, South Celstial Pole SCP and First Point of Libra æ while the Solstitial Colure runs from the NCP through First Point of Cancer ã, SCP and First Point of Capricorn é. 17.2.3 Ecliptical Coordinates The earth’s orbit around the sun, i.e., the ecliptic, defines the “equatorial line” of this coordinate system, which is traditionally used when computing the coordinates for planets. The zero point of ecliptical longitude λ is the same as for equatorial coordinates, and the ecliptical latitude β is counted positive towards the Northern Ecliptical Pole NEP in the constellation of Draco. Moon and sun (and to a much lesser extent, the other planets) pull on the equatorial bulge and try to put Earth’s axis normal to its orbital plane. Earth acts like a spinning top and evades this pull in a sideways motion, so that earth’s axis seems to describe a small circle over a period of almost 26.000 years (see section 17.8). In addition, ecliptic obliquity against the equatorial coordinates, which mirrors the earth’s axial tilt, slowly changes. Therefore, also for ecliptical coordinates is is required to specify which date the coordinates refer to. Stellarium can draw two grids for Ecliptical coordinates. Use the , key to draw the ecliptic for the simulation time. The Markings dialog (4.4.3) allows you to show also a line for epoch J2000.0 and grids for the ecliptical coordinates for current epoch and epoch J2000.0. You can assign your own shortcut keys (section 4.7.1) if you frequently operate with these coordinates. Since version 0.14.0 Stellarium can very accurately show the motions between the coordinate systems (Vondrák, Capitaine, and Wallace, 2011; Vondrák, Capitaine, and Wallace, 2012), and it is quite interesting to follow these motions for several millennia. To support such demonstrations, Stellarium can also draw the precession circles between celestial and ecliptical poles (activate them in the Markings dialog (4.4.3). If you observe long enough, you will see that these circles vary in size, reflecting the changes in ecliptic obliquity. Many of the minor bodies are best observed around the times of their opposition. Stellarium can display a great circle in the ecliptical coordinates which runs through the ecliptic poles and through the sun, thereby allowing to estimate opposition and conjunction. Activate display of this Opposition/Conjunction Line in the Markings dialog (Labeled “O./C. longitude”; 4.4.3). It is interesting to note that star catalogs before T YCHO B RAHE’s (1546–1601), most notably the one in P TOLEMY’s Almagest, used Ecliptical coordinates. The reason is simple: It was known since H IPPARCHUS that stellar coordinates slowly move along the ecliptic through precession, and the correction to coordinates of a date of interest was a simple addition of a linear correction to the ecliptical longitude in the catalog. Changes of ecliptic obliquity was discovered much later. Chapter 17. Astronomical Concepts 196 17.2.4 Galactic Coordinates The Milky Way appears to run along a great circle over the sky, mirroring the fact that the sun is a star in it. Coordinates for non-stellar objects which belong to the Milky Way like pulsars or planetary nebulae are often mapped in Galactic Coordinates, where galactic longitude l and galactic latitude b are usually given in decimal degrees. Here, the zero point of galactic longitudes lies in the Galactic Center. Stellarium can also draw a galactic grid and the galactic equator by activating the respective options in the Markings dialog (see section 4.4.3). You can assign a keyboard shortcut if you frequently use these coordinates (see 4.7.1). 17.3 Distance As D OUGLAS A DAMS (1952–2001) pointed out in The Hitchhiker’s Guide to the Galaxy (Adams, 1981), Space [. . . ] is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to space.[p.76] Astronomers use a variety of units for distance that make sense in the context of the mind-boggling vastness of space. Astronomical Unit (AU) This is the mean Earth-Sun distance. Roughly 150 million kilometres (1.49598 × 108 km). The AU is used mainly when discussing the solar system – for example the distance of various planets from the Sun. Light year (LY) A light year is not, as some people believe, a measure of time. It is the distance that light travels in a year. The speed of light being approximately 300,000 kilometres per second means a light year is a very large distance indeed, working out at about 9.5 trillion kilometres (9.46073 × 1012 km). Light years are most frequently used when describing the distance of stars and galaxies or the sizes of large-scale objects like galaxies, nebulae etc. Parsec (pc) A parsec is defined as the distance of an object that has an annual parallax of 1 second of arc. This equates to 3.26156 light years (3.08568 × 1013 km). Parsecs (and derivatives: kiloparsec kpc, megaparsec Mpc) are most frequently used when describing the distance of stars or the sizes of large-scale objects like galaxies, nebulae etc. 17.4 Time The length of a day is defined as the amount of time that it takes for the Sun to travel from the highest point in the sky at mid-day to the next high-point on the next day. In astronomy this is called a solar day. The apparent motion of the Sun is caused by the rotation of the Earth. However, in this time, the Earth not only spins, it also moves slightly round its orbit. Thus in one solar day the Earth does not spin exactly 360◦ on its axis. Another way to measure day length is to consider how long it takes for the Earth to rotate exactly 360◦ . This is known as one sidereal day. Figure 17.3 illustrates the motion of the Earth as seen looking down on the Earth orbiting the Sun. The red triangle on the Earth represents the location of an observer. The figure shows the Earth at four times: 1. The Sun is directly overhead - it is mid-day. 2. Twelve hours have passed since 1. The Earth has rotated round and the observer is on the opposite side of the Earth from the Sun. It is mid-night. The Earth has also moved round in its orbit a little. 3. The Earth has rotated exactly 360◦ . Exactly one sidereal day has passed since 1. 17.4 Time 197 Figure 17.3: Sidereal day 4. It is mid-day again – exactly one solar day since 1. Note that the Earth has rotated more than 360◦ since 1. It should be noted that in figure 17.3 the sizes of the Sun and Earth and not to scale. More importantly, the distance the Earth moves around its orbit is much exaggerated. The Earth takes a year to travel round the Sun – 365 14 solar days. The length of a sidereal day is about 23 hours, 56 minutes and 4 seconds. 17.4.1 Sidereal Time It takes exactly one sidereal day for the celestial sphere to make one revolution in the sky. Astronomers find sidereal time useful when observing. This is the Right Ascension which is currently passing the meridian line. When visiting observatories, look out for doctored alarm clocks that have been set to run in sidereal time! 17.4.2 Julian Day Number In the 19th century, astronomer J OHN H ERSCHEL (1792–1871) introduced the use of Julian Day numbers (invented around the time of the Gregorian calendar reform). This is a simple continuous day count starting on January 1, -4712 (4713 BC). There are no years, months etc., and the integral day number switches at noon, so during a single night of observation (in Europe) the date never changes. The fractional part of the number is just the fraction of day that has elapsed since last noon. Given that a day has 86400 seconds, we should give a JD with 5 decimal places to capture the nearest second. This causes a problem for modern computers: even a “double precision float” can keep Chapter 17. Astronomical Concepts 198 only about 13 decimal places. More than 2.4 million days have passed, so that e.g. January 1, 2000, 12:00UT is 2451545.0, which is an accurately storable number with 7 decimal places, but 12:34:56UT is computed as 2451545.02426. A more accurate result would yield 2451545.024259259259... So, for a field where sub-second accuracy became crucial like spacecraft operations, the Modified Julian Day (MJD) has been introduced. It is simply MJD = JD − 2400000.5. (17.1) This means, days start at midnight, and the (constant, in our era) decimal places of the “big numbers” at the begin of the number have been traded in for more decimal places at the end. Don’t put your expectations too high when you see MJD displayed (section 4.1): Stellarium uses a double-precision floating point number for JD for internal timekeeping, and Stellarium’s display of MJD is simply computed from it. So you cannot set temporal increments smaller than a second, and it hardly would make sense to expect more accuracy from the simulation algorithms. 17.4.3 Delta T Until around 1900, the earth’s rotation was regarded as perfect standard of time. There were 86400 seconds per mean solar day, and the accuracy of reproducing time with mechanical clocks only in this time started to become as good as the earth’s rotation itself. Astronomers who computed solar eclipses reported in texts from antiquity wondered about a required time shift which they originally attributed to a yet-unknown “secular acceleration of the lunar motion”. However, it turned out that indeed the gravitational effect of the moon which causes the tides also has effects on earth’s rotation: the tides slowly break earth’s rotational speed. The energy is also transferred to the moon, and the acceleration leads to the moon slowly moving away from the earth4 . This led to the introduction of a time named Ephemeris Time (ET) with progresses in the speed of the second in the year 1900, to be used for positional computation in our solar system, in addition to Greenwich Mean Time (GMT), from which all zone times and “civil” clock times were derived. The introduction of Atomic Clocks in the middle of the 20th century led to a redefinition of the (temporal) second, which has been de-coupled from earth’s rotation. This time, the International Atomic Time TAI, is the basis for Terrestrial Time TT which can be considered as constantly progressing at constant speed5 , and is used for computation of the planetary positions. Still, people living on earth prefer to have the mean solar noon governing the run of day and night. Therefore all forms of civil time are linked to Coordinated Universal Time UTC. Seconds in UTC and TAI are of equal length. The slow and irregular divergence between TAI and UTC is observed by a few standardisation institutes. When necessary, a leap second can be introduced to the UTC to bring the earth’s rotation back in sync so that the Mean Sun again culminates at noon. The difference ∆T = T T −UT (or “Delta T”) describes the temporal offset which amounts already to more than a minute in the 21st century. There have been many attempts to properly model ∆T , and Stellarium offers several models you can choose from in the configuration dialog (see section 4.3.3). The default, “Espenak and Meeus (2006)”, is a widely accepted standard. But if you are a researcher and want to experiment with alternative models, you will hopefully like this feature. you can even specify your own data for a, b, c, y and the secular term for lunar acceleration n 4 No need to worry, the moon recedes from the earth only a few centimeters per year as measured with the laser reflectors left by the Apollo astronauts in the 1970s. In a very far future, however, there will only be annular solar eclipses as a consequence! 5 We don’t discuss relativity here. The advanced reader is referred to the presentation in the Wikipedia, 17.4 Time 199 (actually ṅ = dn/dt in units of arcseconds/century2 ) if you can model ∆T according to the formula = a + b · u + c · u2 where (17.2) year − y u = (17.3) 100 List of ∆T models in Stellarium The following list describes sources and a few details about the models for ∆T implemented in Stellarium. Without correction. Correction is disabled. Use only if you know what you are doing! Schoch (1931). This historical formula was obtained by Schoch (1931) and was also used in “A New Test of Einstein’s Theory of Relativity by Ancient Solar Eclipses” (Henriksson, 2009). See for more in Peters (2010). ṅ = −29.6800 /cy2 . Clemence (1948). This empirical equation was published in “On the system of astronomical constants” (Clemence, 1948). Valid range of usage: between years 1681 and 1900. ṅ = −22.4400 /cy2 . IAU (1952). This formula is based on a study of post-1650 observations of the Sun, the Moon and the planets (Spencer Jones, 1939) and reproduced in Astronomical Formulae for Calculators (Meeus, 1988). It was also adopted in the PC program SunTracker Pro. Valid range of usage: between years 1681 and 1936. ṅ = −22.4400 /cy2 . Astronomical Ephemeris (1960). This is a slightly modified version of the IAU 1952 (Spencer Jones, 1939) formula which was adopted in the “Astronomical Ephemeris” (Wilkins, 1961) and in the Canon of Solar Eclipses -2003 to +2526 (Mucke and Meeus, 1983). Valid range of usage: between years -500 and 2000. ṅ = −22.4400 /cy2 . Tuckerman (1962, 1964) & Goldstine (1973). The famous tables (Tuckerman, 1962; Tuckerman, 1964) list the positions of the Sun, the Moon and the planets at 5- and 10-day intervals from 601 BCE to 1649 CE. The same relation was also implicitly adopted in the syzygy tables of Goldstine (1973). Valid range of usage: between years -600 and 1649. Muller & Stephenson (1975). This equation was published in “The accelerations of the earth and moon from early astronomical observations” (Muller and F. R. Stephenson, 1975). Valid range of usage: between years -1375 and 1975. ṅ = −37.500 /cy2 . Stephenson (1978). This equation was published in “Pre-Telescopic Astronomical Observations” (F. R. Stephenson, 1978). ṅ = −30.000 /cy2 . Schmadel & Zech (1979). This 12th-order polynomial equation (outdated and superseded by Schmadel and Zech (1988)) was published in “Polynomial approximations for the correction delta T E.T.-U.T. in the period 1800-1975” (Schmadel and Zech, 1979) as fit through data published by Brouwer (1952). Valid range of usage: between years 1800 and 1975, with meaningless values outside this range. ṅ = −23.894600 /cy2 . Morrison & Stephenson (1982). This algorithm Morrison and F. R. Stephenson, 1982 was adopted in Planetary Programs and Tables from –4000 to +2800 (Pierre Bretagnon and Simon, 1986) and in the PC planetarium program RedShift. Valid range of usage: between years -4000 and 2800. ṅ = −26.000 /cy2 . Stephenson & Morrison (1984). This formula was published in “Long-term changes in the rotation of the earth - 700 B.C. to A.D. 1980” (F. R. Stephenson and Morrison, 1984). Valid range of usage: between years -391 and 1600. ṅ = −26.000 /cy2 . Stephenson & Houlden (1986). This algorithm (Houlden and F. Stephenson, 1986) is used in the PC planetarium program Guide 7. Valid range of usage: between years -600 and 1600. ṅ = −26.000 /cy2 . Espenak (1987, 1989). This algorithm was given in Fifty Year Canon of Solar Eclipses: 1986 – 2035 (Espenak, 1987) and in Fifty Year Canon of Lunar Eclipses: 1986 – 2035 (Espenak, 1989). Valid range of usage: between years 1950 and 2100. ∆T 200 Chapter 17. Astronomical Concepts Borkowski (1988). This formula was obtained by Borkowski (1988) from an analysis of 31 solar eclipse records dating between 2137 BCE and 1715 CE. Valid range of usage: between years -2136 and 1715. ṅ = −23.89500 /cy2 . Schmadel & Zech (1988). This 12th-order polynomial equation was published in “Empirical Transformations from U.T. to E.T. for the Period 1800-1988” (Schmadel and Zech, 1988) as data fit through values given by F. R. Stephenson and Morrison (1984). Valid range of usage: between years 1800 and 1988, with a mean error of less than one second, max. error 1.9s, and meaningless values outside this range. ṅ = −26.000 /cy2 . Chapront-Touze & Chapront (1991). This formula was adopted by M. Chapront-Touze & J. Chapront in the shortened version of the ELP 2000-85 lunar theory in their Lunar Tables and Programs from 4000 B.C. to A.D. 8000 (Chapront-Touzé and Chapront, 1991). The relations are based on those of F. R. Stephenson and Morrison (1984), but slightly modified to make them compatible with the tidal acceleration parameter of ṅ = −23.894600 /cy2 adopted in the ELP 2000-85 lunar theory (Chapront-Touzé and Chapront, 1988a). Stephenson & Morrison (1995). This equation was published in “Long-Term Fluctuations in the Earth’s Rotation: 700 BC to AD 1990” (F. R. Stephenson and Morrison, 1995). Valid range of usage: between years -700 and 1600. ṅ = −26.000 /cy2 . Stephenson (1997). F. R. Stephenson published this formula in his book Historical Eclipses and Earth’s Rotation (F. Richard Stephenson, 1997). Valid range of usage: between years -500 and 1600. ṅ = −26.000 /cy2 . Meeus (1998) (with Chapront, Chapront-Touze & Francou (1997)). From Astronomical Algorithms (Meeus, 1998), and widely used. Table for 1620..2000, and includes a variant of Chapront, Chapront-Touze & Francou (1997) for dates outside 1620..2000. Valid range of usage: between years -400 and 2150. ṅ = −25.737600 /cy2 . JPL Horizons. The JPL Solar System Dynamics Group of the NASA Jet Propulsion Laboratory use this formula in their interactive website JPL Horizons6 . Valid range of usage: between years -2999 and 1620, with zero values outside this range. ṅ = −25.737600 /cy2 . Meeus & Simons (2000). This polynome was published in “Polynomial approximations to Delta T, 1620-2000 AD” (Meeus and Simons, 2000). Valid range of usage: between years 1620 and 2000, with zero values outside this range. ṅ = −25.737600 /cy2 . Montenbruck & Pfleger (2000). The fourth edition of Astronomy on the Personal Computer (Montenbruck and Pfleger, 2000) provides simple 3rd-order polynomial data fits for the recent past. Valid range of usage: between years 1825 and 2005, with a typical 1-second accuracy and zero values outside this range. Reingold & Dershowitz (2002, 2007). E. M. Reingold & N. Dershowitz present this polynomial data fit in Calendrical Calculations (Reingold and Dershowitz, 2007) and in their Calendrical Tabulations 1900-2200 (Reingold and Dershowitz, 2002). It is based on Astronomical Algorithms (Meeus, 1991). Morrison & Stephenson (2004, 2005). This important solution was published in “Historical values of the Earth’s clock error ∆T and the calculation of eclipses” (Morrison and F. R. Stephenson, 2004) with addendum (Morrison and F. R. Stephenson, 2005). Valid range of usage: between years -1000 and 2000. ṅ = −26.000 /cy2 . Stephenson, Morrison & Hohenkerk (2016). This important new solution was published in “Measurement of the Earth’s rotation: 720 BC to AD 2015” (F. R. Stephenson, Morrison, and Hohenkerk, 2016). The solution combines a spline fit to observations (used between the given limits) with a parabolic fit (used as fallback outside the range, but without smooth transitions at the limits, i.e., values for 2016 and later deviate notably from current estimates, and should not be used for dates after 2015). Recommended range of usage: between years 6 17.5 Angles 201 -720.0 and 2016.0 ṅ = −25.8200 /cy2 . Espenak & Meeus (2006). This solution7 by F. Espenak and J. Meeus, based on Morrison and F. R. Stephenson (2004) and a polynomial fit through tabulated values for 1600-2000, is used for the NASA Eclipse Web Site8 and in their Five Millennium Canon of Solar Eclipses: -1900 to +3000 (Espenak and Meeus, 2006). This formula is also used in the solar, lunar and planetary ephemeris program SOLEX. Valid range of usage: between years -1999 and 3000. ṅ = −25.85800 /cy2 . Reijs (2006). From the Length of Day (LOD; as determined by Morrison and F. R. Stephenson (2004)), Victor Reijs derived a ∆T formula by using a Simplex optimisation with a cosine and square function9 . This is based on a possible periodicy described by Morrison and F. R. Stephenson (2004). Valid range of usage: between years -1500 and 1100. ṅ = −26.000 /cy2 . Banjevic (2006). This solution is based on F. R. Stephenson and Morrison (1984) and was published in “Ancient eclipses and dating the fall of Babylon” (Banjevic, 2006). Valid range of usage: between years -2020 and 1620, with zero values outside this range. ṅ = −26.000 /cy2 . Islam, Sadiq & Qureshi (2008, 2013). This solution by S. Islam, M. Sadiq and M. S. Qureshi, based on Meeus and Simons (2000), was published in “Error Minimization of Polynomial Approximation of Delta T” (Islam, Sadiq, and Qureshi, 2008) and revisited by Sana Islam in 2013. Valid range of usage: between years 1620 and 2007, with zero values outside this range. Khalid, Sultana & Zaidi (2014). This polynomial approximation with 0.6 seconds of accuracy was published in “Delta T: Polynomial Approximation of Time Period 1620–2013” (Khalid, Sultana, and Zaidi, 2014). Valid range of usage: between years 1620 and 2013, with zero values outside this range. Custom equation of ∆T . This is a quadratic formula for calculation of ∆T with coefficients defined by the user. 17.5 Angles Astronomers typically use degrees to measure angles. Since many observations require very precise measurement, the degree is subdivided into sixty minutes of arc also known as arc-minutes. Each minute of arc is further subdivided into sixty seconds of arc, or arc-seconds. Thus one degree is equal to 3600 seconds of arc. Finer grades of precision are usually expressed using the SI prefixes with arc-seconds, e.g. milli arc-seconds (one milli arc-second is one thousandth of an arc-second). 17.5.1 Notation Degrees are denoted using the ◦ symbol after a number. Minutes of arc are denoted with a 0 , and seconds of arc are denoted using 00 . Angles are frequently given in two formats: 1. DMS format — degrees, minutes and seconds. For example 90◦ 150 1200 . When more precision is required, the seconds component may include a decimal part, for example 90◦ 150 12.43200 . 2. Decimal degrees, for example 90.2533◦ 17.5.2 Handy Angles Being able to estimate angular distance can be very useful when trying to find objects from star maps in the sky. One way to do this with a device called a crossbow. 7 This solution is used by default. 8 9 Chapter 17. Astronomical Concepts 202 Crossbows are a nice way get an idea of angular distances, but carrying one about is a little cumbersome. A more convenient alternative is to hold up an object such as a pencil at arm’s length. If you know the length of the pencil, d, and the distance of it from your eye, D, you can calculate its angular size, θ using this formula:  d θ = 2 · arctan 2·D  (17.4) Another, more handy (ahem!) method is to use the size of your hand at arm’s length: Tip of little finger About 1◦ Middle three fingers About 4◦ Across the knuckles of the fist About 10◦ Open hand About 18◦ Using you hand in this way is not very precise, but it’s close enough to give you some way to translate an idea like “Mars will be 45◦ above the Southeastern horizon at 21:30”. Of course, there is variation from person to person, but the variation is compensated for somewhat by the fact that people with long arms tend to have larger hands. In exercise 20.2 you will work out your own “handy angles”. 17.6 The Magnitude Scale When astronomers talk about magnitude, they are referring to the brightness of an object. How bright an object appears to be depends on how much light it is giving out and how far it is from the observer. Astronomers separate these factors by using two measures: absolute magnitude (Mag or M) which is a measure of how much light is being given out by an object, and apparent magnitude (mag or m) which is how bright something appears to be in the sky. For example, consider two 100 watt lamps, one which is a few meters away, and one which is a kilometre away. Both give out the same amount of light – they have the same absolute magnitude. However the nearby lamp seems much brighter – it has a much greater apparent magnitude. When astronomers talk about magnitude without specifying whether they mean apparent or absolute magnitude, they are usually referring to apparent magnitude. The magnitude scale has its roots in antiquity. The Greek astronomer H IPPARCHUS defined the brightest stars in the sky to be first magnitude, and the dimmest visible to the naked eye to be sixth magnitude. In the 19th century British astronomer N ORMAN P OGSON (1829–1891) quantified the scale more precisely, defining it as a logarithmic scale where a magnitude 1 object is 100 times as bright as a magnitude 6 object (a difference of five magnitudes). The zero-point of the modern scale was originally defined as the brightness of the star Vega, however this was re-defined more formally in 1982 (Aller et al., 1989). Objects brighter than Vega are given negative magnitudes. The absolute magnitude of a star is defined as the magnitude a star would appear if it were 10 parsecs from the observer. Table 17.1 lists several objects that may be seen in the sky, their apparent magnitude and their absolute magnitude where applicable (only stars have an absolute magnitude value. The planets and the Moon don’t give out light like a star does – they reflect the light from the Sun). 17.7 Luminosity Luminosity is an expression of the total energy radiated by a star. It may be measured in watts, however, astronomers tend to use another expression — solar luminosities where an object with twice the Sun’s luminosity is considered to have two solar luminosities and so on. Luminosity is related to absolute magnitude. 17.8 Precession 203 Object m The Sun -27 Vega 0.05 Betelgeuse 0.47 Sirius (the brightest star) -1.5 Venus (at brightest) -4.4 Full Moon (at brightest) -12.6 M 4.8 0.6 -7.2 1.4 — — Table 17.1: Magnitudes of a few objects 17.8 Precession Figure 17.4: Ecliptic obliquity As the Earth orbits the Sun throughout the year, the axis of rotation (the line running through the rotational poles of the Earth) seems to point towards the same position on the celestial sphere, as can be seen in figure 17.4. The angle between the axis of rotation and the perpendicular of the orbital plane is called the obliquity of the ecliptic. It is currently about 23◦ 270 and is the angle between equatorial coordinates (17.2.2) and ecliptical coordinates (17.2.3). Observed over very long periods of time the direction the axis of rotation points to does actually change. The angle between the axis of rotation and the orbital plane stays fairly constant, but the direction the axis points — the position of the celestial pole — transcribes a figure similar to a circle on the stars in the celestial sphere. The motion is similar to the way in which a gyroscope slowly twists, as figure 17.5 illustrates. This process is called precession. The circles can be shown in Stellarium: From the View menu ( F4 ), tab “Markings”, switch on “Precession Circles” (4.4.3). Precession is a slow process. The axis of rotation twists through a full 360◦ about once every 26,000 years. However, over these long times other gravitational perturbations (“planetary precession”) play a role, and what may be thought of as rigid “precession circle” can actually only show the instantaneous (current) state. Over millennia the circle slightly varies. Precession has some important implications: 1. RA/Dec coordinates change over time, albeit slowly. Measurements of the positions of stars recorded using RA/Dec coordinates must also include a date (“equinox”) for those coordinates. Therefore the current star catalogues list their objects for the epoch and equinox J2000.0. 2. Polaris, the pole star, won’t stay a good indicator of the location of the Northern celestial pole. In 14,000 years time Polaris will be nearly 47◦ away from the celestial pole! Chapter 17. Astronomical Concepts 204 Figure 17.5: Precession Precession Shift of Stars on the Horizon 085 90 95 100 105 110 115 120 125 130 135 Zet Pup -100 Sirius Gam Cen -200 Sig Sgr Eps Sgr Lam Sco -300 Antares -400 The Cen Spica -500 The Sco Alphard -600 Deneb Kaitos Del CMa -700 Alnitak Alnilam Mintaka Betelgeuse Gam Ori -800 Eps CMa Bet CMa Kap Ori Lam Vel -900 Rigel -1000 Azimuth 90 95 100 Geograpical Latitude: 30°0’ 0’’. Stars to mag=2.25. Azimuths from North, without refraction. 105 110 115 120 125 130 135 © Georg Zotti 2010, Figure 17.6: Precession: Change of rising positions of the stars along the eastern horizon from azimuths 85 to 135 degrees, between years 1000 BC and 0, for latitude ϕ = 30◦ . 17.9 Parallax 205 3. The change in declination causes a shift in the rising and setting positions of the stars along the horizon. Figure 17.6 shows part of the horizon for latitude ϕ = 30◦ North. For a given year (left vertical labels), make a horizontal line to find rising azimuth of the bright stars indicated by the twisting lines. Depending on where on the celestial sphere a star is located, it may appear to move north or south, or be almost stationary for several centuries. 17.9 Parallax Parallax is the change of angular position of two stationary points relative to each other as seen by an observer, due to the motion of said observer. Or more simply put, it is the apparent shift of an object against a background due to a change in observer position. This can be demonstrated by holding ones thumb up at arm’s length. Closing one eye, note the position of the thumb against the background. After swapping which eye is open (without moving), the thumb appears to be in a different position against the background. 17.9.1 Geocentric and Topocentric Observations When computing planetary positions was done manually by adding numbers tabulated in yearly almanacs, computing the Earth’s position and, say, position of a minor planet was usually good enough to find the object in the sky. In both cases, the exact numbers refer to the gravitational centres of the respective bodies. However, we are sitting on Earth’s surface, so the observed planet will be seen in a slightly shifted location. The amount for objects in the inner solar system is usually just a few arcseconds and is mostly negligible when we just want to find an object. But it makes a difference when it comes to observations of stellar occultations by planets or asteroids. Such a body may measure only a few tens of kilometres, and the shadow track which it leaves on Earth’s surface is of approximately the same size.10 A much closer and bigger object is the Moon, which can also occult stars. It can even occult the one big star we call the Sun: this is a Solar Eclipse. And here it makes a huge difference where on the planet you are located. If you are interested in astronomical computing, you may still be interested in geocentric numerical results. From the Settings panel ( F2 ), tab “Tools”, there is a checkbox for “Topocentric Coordinates”. Switch it off to put yourself into the center of the planet you are located. 17.9.2 Stellar Parallax A similar thing happens due to the Earth’s motion around the Sun. Nearby stars appear to move against more distant background stars, as illustrated in figure 17.7. The movement of nearby stars against the background is called stellar parallax, or annual parallax. Since we know the distance the radius of the Earth’s orbit around the Sun from other methods, we can use simple geometry to calculate the distance of the nearby star if we measure annual parallax. As can be seen from figure 17.7, the annual parallax p is half the angular distance between the apparent positions of the nearby star. The distance of the nearby object is d. Astronomers use a unit of distance called the parsec ( pc) which is defined as the distance at which a nearby star has p = 100 . Even the nearest stars exhibit very small movement due to parallax. The closest star to the Earth other than the Sun is Proxima Centauri. It has an annual parallax of 0.7719900 , corresponding to a distance of 1.295 pc (4.22 light years). 10 Unfortunately Stellarium (as of v0.15.0) is not accurate enough to reliably compute such occultations. Even a deviation of 0.5 arcseconds is too much here. 206 Chapter 17. Astronomical Concepts Figure 17.7: Stellar Parallax Even with the most sensitive instruments for measuring the positions of the stars it is only possible to use parallax to determine the distance of stars up to about 1,600 light years from the Earth, after which the annual parallax is so small it cannot be measured accurately enough. In Stellarium, the annual parallax can be listed in the object information for stars when available. It is not used for the positional calculations. 17.10 Proper Motion Proper motion is the change in the position of a star over time as a result of its motion through space relative to the Sun. It does not include the apparent shift in position of star due to annular parallax. The star exhibiting the greatest proper motion is Barnard’s Star which moves more than ten seconds of arc per year. If you want to simulate the effect of proper motion with Stellarium, put the map into equatorial view mode, switch off ground and cardinal marks, and set some high time lapse speed. You will see a few stars change their locations quite soon, those are usually stars in our galactic neighbourhood (see section 20.12). Note however some limitations: 1. Stellarium will stop at ±100.000 years. This limit may be still suitable for most stellar locations. The planetary locations are not trustworthy outside of a much narrower temporal window (see section F). You cannot simulate the sky over the dinosaurs or such things. 2. Proper motion is only modelled by the linear components. True 3D motion in space requires more computation, which would slow down the program. 3. Double stars are listed in catalogs as two individual stars with their current proper motion which consists of spatial motion and the orbital motion around their center of gravity. They may be seen flying apart, which is of course not realistic. 18. Astronomical Phenomena BARRY G ERDES , WITH ADDITIONS BY G EORG Z OTTI This chapter focuses on the observational side of astronomy — what we see when we look at the sky. 18.1 The Sun Without a doubt, the most prominent object in the sky is the Sun. The Sun is so bright that when it is in the sky, its light is scattered by the atmosphere to such an extent that almost all other objects in the sky are rendered invisible. The Sun is a star like many others but it is much closer to the Earth at approximately 150 million kilometres (a distance also called 1 Astronomical Unit). The next nearest star, Proxima Centauri is approximately 260,000 times further away from us than the Sun! The Sun is also known by its Latin name, Sol. Over the course of a year, the Sun appears to move round the celestial sphere in a great circle known as the ecliptic. Stellarium can draw the ecliptic on the sky. To toggle drawing of the ecliptic, press the , key. WARNING: Looking at the Sun can permanently damage the eye. Never look at the Sun without using the proper filters! By far the safest way to observe the Sun it to look at it on a computer screen, courtesy of Stellarium! 18.2 Stars The Sun is just one of billions of stars. Even though many stars have a much greater absolute magnitude than the Sun (they give out more light), they have an enormously smaller apparent magnitude due to their large distance. Stars have a variety of forms — different sizes, brightnesses, temperatures, and colours. Measuring the position, distance and attributes of the stars is known as astrometry, and is a major part of observational astronomy. 208 18.2.1 Chapter 18. Astronomical Phenomena Multiple Star Systems Many stars have stellar companions. As many as six stars can be found orbiting one-another in close associations known as multiple star systems — binary systems being the most common with two stars. Multiple star systems are more common than solitary stars, putting our Sun in the minority group. Sometimes multiple stars orbit each other in a way that means one will periodically eclipse the other. These are eclipsing binaries or Algol variables. Optical Doubles & Optical Multiples Sometimes two or more stars appear to be very close to one another in the sky, but in fact have great separation, being aligned from the point of view of the observer but of different distances. Such pairings are known as optical doubles and optical multiples. 18.2.2 Constellations The constellations are groupings of stars that are visually close to one another in the sky. The actual groupings are fairly arbitrary — different cultures have grouped stars together into different constellations. In many cultures, the various constellations have been associated with mythological entities. As such people have often projected pictures into the skies as can be seen in figure 18.1 which shows the constellation of Ursa Major. On the left is a picture with the image of the mythical Great Bear, on the right only a line-art version (or stick figure) is shown. The seven bright stars of Ursa Major are widely recognised, known variously as “the plough”, the “pan-handle”, and the “big dipper”. This sub-grouping is known as an asterism — a distinct grouping of stars. On the right, the picture of the bear has been removed and only a constellation diagram remains. Figure 18.1: Ursa Major Stellarium can draw both constellation diagrams and artistic representations of the constellations. Multiple sky cultures are supported: Western, Polynesian, Egyptian, Chinese, and several other sky cultures are available, although at time of writing the non-Western constellations are not complete, and as yet there are no artistic representations of these sky-cultures. Aside from historical and mythological value, to the modern astronomer the constellations provide a way to segment the sky for the purposes of describing locations of objects, indeed one of the first tasks for an amateur observer is learning the constellations — the process of becoming familiar with the relative positions of the constellations, at what time of year a constellation is visible, and in which constellations observationally interesting objects reside. The International 18.2 Stars 209 Astronomical Union has adopted 88 “Western” constellations as a common system for segmenting the sky. They are based on Greek/Roman mythology, but with several additions from Renaissance and later centuries. As such some formalisation has been adopted, each constellation having a proper name, which is in Latin, and a three letter abbreviation of that name. For example, Ursa Major has the abbreviation UMa. Also, the “Western” constellation have clearly defined boundaries (Delporte, 1930), which you can draw in Stellarium when you press the B key1 . The IAU constellation a selected object is placed in is also available in the object information data (Roman, 1987), regardless of the currently active skyculture. On the other hand, the shapes of mythological figures, and also stick figures, have not been canonized, so you will find deviations between Stellarium and printed atlases. 18.2.3 Star Names Stars can have many names. The brighter stars often have common names relating to mythical characters from the various traditions. For example the brightest star in the sky, Sirius is also known as The Dog Star (the name Canis Major — the constellation Sirius is found in — is Latin for “The Great Dog”). Most bright names have been given names in antiquity. P TOLEMY’s most influential book, the Syntaxis, was translated to the Arab language in the age of early Muslim scientists. When, centuries later, the translation, called Almagest, was re-introduced to the re-awakening European science, those names, which often only designated the position of the star within the figure, were taken from the books, often misspelled, and used henceforth as proper names. A few more proper names have been added later, sometimes dedicatory names added by court astronomers into their maps. There are also 3 stars named after the victims of the Apollo 1 disaster in 1967. Today, the International Astronomical Union (IAU) is the only scientifically accepted authority which can give proper names to stars. Some companies offer a paid name service for commemoration or dedication of a star for deceased relatives or such, but all you get here is a piece of paper with coordinates of (usually) an unremarkably dim star only visible in a telescope, and a name to remember, stored (at best) in the company’s database. There are several more formal naming conventions that are in common use. Bayer Designation German astronomer J OHANN BAYER (1572–1625) devised one such system for his atlas, the Uranographia, first published in 1603. His scheme names the stars according to the constellation in which they lie prefixed by a lower case Greek letter, starting at α for (usually) the brightest star in the constellation and proceeding with β , γ, . . . in descending order of apparent magnitude. For example, such a Bayer Designation for Sirius is “α Canis Majoris” (note that the genitive form of the constellation name is used; today also the short form α CMa is in use). There are some exceptions to the descending magnitude ordering, and some multiple stars (both real and optical) are named with a numerical superscript after the Greek letter, e.g. π 1 ... π 6 Orionis. Flamsteed Designation English astronomer J OHN F LAMSTEED (1646–1719) numbered stars in each constellation in order of increasing right ascension followed by the genitive form of the constellation name, for example “61 Cygni” (or short: “61 Cyg”). 1 These boundaries or borders have been drawn using star maps from 1875. these borders are no longer parallel to today’s coordinates. Due to the effect of precession, 210 Chapter 18. Astronomical Phenomena Hipparcos Hipparcos (for High Precision Parallax Collecting Satellite) was an astrometry mission of the European Space Agency (ESA) dedicated to the measurement of stellar parallax and the proper motions of stars. The project was named in honour of the Greek astronomer H IPPARCHUS. Ideas for such a mission dated from 1967, with the mission accepted by ESA in 1980. The satellite was launched by an Ariane 4 on 8 August 1989. The original goal was to place the satellite in a geostationary orbit above the earth, however a booster rocket failure resulted in a highly elliptical orbit from 315 to 22,300 miles altitude. Despite this difficulty, all of the scientific goals were accomplished. Communications were terminated on 15 August 1993. The program was divided in two parts: the Hipparcos experiment whose goal was to measure the five astrometric parameters of some 120,000 stars to a precision of some 2 to 4 milli arc-seconds and the Tycho experiment, whose goal was the measurement of the astrometric and two-colour photometric properties of some 400,000 additional stars to a somewhat lower precision. The final Hipparcos Catalogue (120,000 stars with 1 milli arc-second level astrometry) and the final Tycho Catalogue (more than one million stars with 20-30 milli arc-second astrometry and two-colour photometry) were completed in August 1996. The catalogues were published by ESA in June 1997. The Hipparcos and Tycho data have been used to create the Millennium Star Atlas: an all-sky atlas of one million stars to visual magnitude 11, from the Hipparcos and Tycho Catalogues and 10,000 non-stellar objects included to complement the catalogue data. There were questions over whether Hipparcos has a systematic error of about 1 milli arc-second in at least some parts of the sky. The value determined by Hipparcos for the distance to the Pleiades is about 10% less than the value obtained by some other methods. By early 2004, the controversy remained unresolved. Stellarium uses the Hipparcos Catalogue for star data, as well as having traditional names for many of the brighter stars. The stars tab of the search window allows for searching based on a Hipparcos Catalogue number (as well as traditional names), e.g. the star Sadalmelik in the constellation of Aquarius can be found by searching for the name, or its Hipparcos number, 109074. Figure 18.2 shows the information Stellarium displays when a star is selected. At the top, the common name, Bayer/Flamsteed designations and Hipparcos number are shown, followed by the RA/Dec coordinates, apparent magnitude, distance and other data. Figure 18.2: Star Names and Data 18.2.4 Spectral Type & Luminosity Class Stars have many different colours. Seen with the naked eye most appear to be white, but this is due to the response of the eye — at low light levels the eye is not sensitive to colour. Typically 18.2 Stars 211 Spectral Type Surface Temperature (K) Star Colour O B A F G K M 28,000—50,000 10,000—28,000 7,500—10,000 6,000—7,500 4,900—6,000 3,500—4,900 2,000—3,500 Blue Blue-white White-blue Yellow-white Yellow Orange Red Table 18.1: Spectral Types the unaided eye can start to see differences in colour only for stars that have apparent magnitude brighter than 1. Betelgeuse, for example has a distinctly red tinge to it, and Sirius appears to be blue, while Vega is the prototype “white” star. By splitting the light from a star using a prism attached to a telescope and measuring the relative intensities of the colours of light the star emits — the spectrum — a great deal of interesting information can be discovered about a star including its surface temperature, and the presence of various elements in its atmosphere. Astronomers groups stars with similar spectra into spectral types, denoted by one of the following letters: O, B, A, F, G, K and M.2 Type O stars have a high surface temperature (up to around 50,000 K) while the at other end of the scale, the M stars are red and have a much cooler surface temperature, typically 3000 K. The Sun is a type G star with a surface temperature of around 5,500 K. Spectral types may be further sub-divided using a numerical suffix ranging from 0-9 where 0 is the hottest and 9 is the coolest. Table 18.1 shows the details of the various spectral types. For about 90% of stars, the absolute magnitude increases as the spectral type tends to the O (hot) end of the scale. Thus the whiter, hotter stars tend to have a greater luminosity. These stars are called main sequence stars. There are however a number of stars that have spectral type at the M end of the scale, and yet they have a high absolute magnitude. These stars are close to the ends of their lives and have a very large size, and consequently are known as giants, the largest of these known as super-giants. There are also stars whose absolute magnitude is very low regardless of the spectral class. These are known as dwarf stars, among them white dwarfs (dying stars) and brown dwarfs (“failed stars”). The luminosity class is an indication of the type of star — whether it is main sequence, a giant or a dwarf. Luminosity classes are denoted by a number in roman numerals, as described in table 18.2. Plotting the luminosity of stars against their spectral type/surface temperature gives a diagram called a Hertzsprung-Russell diagram (after the two astronomers E JNAR H ERTZSPRUNG (1873– 1967) and H ENRY N ORRIS RUSSELL (1877–1957) who devised it). A slight variation of this is shown in figure 18.3 (which is technically a colour/magnitude in figure 18.3 (which is technically a colour/magnitude plot). 18.2.5 Variable Stars Most stars are of nearly constant luminosity. The Sun is a good example of one which goes through relatively little variation in brightness (usually about 0.1% over an 11 year solar cycle). Many stars, 2 The classic mnemonic for students of astrophysics says: “Oh, Be A Fine Girl, Kiss Me”. 212 Chapter 18. Astronomical Phenomena Figure 18.3: Hertzsprung-Russell Diagram 18.3 Our Moon 213 Luminosity class Description Ia, Ib II III IV V VI VII Super-giants Bright giants Normal giants Sub-giants Main sequence Sub-dwarfs White-dwarfs Table 18.2: Luminosity Classification however, undergo significant variations in luminosity, and these are known as variable stars. There are many types of variable stars falling into two categories, intrinsic and extrinsic. Intrinsic variables are stars which have intrinsic variations in brightness, that is, the star itself gets brighter and dimmer. There are several types of intrinsic variables, probably the best-known and most important of which is the Cepheid variable whose luminosity is related to the period with which its brightness varies. Since the luminosity (and therefore absolute magnitude) can be calculated, Cepheid variables may be used to determine the distance of the star when the annual parallax is too small to be a reliable guide. This is especially welcome because they are giant stars, and so they are even visible in neighboring galaxies. Extrinsic variables are stars of constant brightness that show changes in brightness as seen from the Earth. These include rotating variables, stars whose apparent brightness change due to rotation, and eclipsing binaries. Stellarium’s catalogs include many kinds variable stars. See section C.3 for more details. 18.3 Our Moon The Moon is the large satellite which orbits the Earth approximately every 28 days. It is seen as a large bright disc in the early night sky that rises later each day and changes shape into a crescent until it disappears near the Sun. After this it rises during the day then gets larger until it again becomes a large bright disc again. 18.3.1 Phases of the Moon As the moon moves round its orbit, the amount that is illuminated by the sun as seen from a vantage point on Earth changes. The result of this is that approximately once per orbit, the moon’s face gradually changes from being totally in shadow to being fully illuminated and back to being in shadow again. This process is divided up into various phases as described in table 18.3. Chapter 18. Astronomical Phenomena 214 18.4 The Major Planets Unlike the stars whose relative positions remain more or less constant, the planets seem to move across the sky over time (the word “planet” comes from the Greek for “wanderer”). The planets are siblings of the Earth, massive bodies that are in orbit around the Sun. Until 2006 there was no formal definition of a planet, leading to some confusion about the classification for some bodies traditionally regarded as being planets, but which didn’t seem to fit with the others. In 2006 the International Astronomical Union (IAU) defined a planet as a celestial body that, within the Solar System: 1. is in orbit around the Sun 2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape; and 3. has cleared the neighbourhood around its orbit or within another system: 1. is in orbit around a star or stellar remnants 2. has a mass below the limiting mass for thermonuclear fusion of deuterium; and 3. is above the minimum mass/size requirement for planetary status in the Solar System. Moving from the Sun outwards, the 8 major planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Since the formal definition of a planet in 2006 Pluto has been relegated to having the status of dwarf planet, along with bodies such as Ceres and Eris. See figure 18.4. 18.4.1 Terrestrial Planets The planets closest to the sun are called collectively the terrestrial planets. The terrestrial planets are: Mercury, Venus, Earth and Mars. The terrestrial planets are relatively small, comparatively dense, and have solid rocky surface. Most of their mass is made from solid matter, which is mostly rocky and/or metallic in nature. 18.4.2 Jovian Planets Jupiter, Saturn, Uranus and Neptune make up the Jovian planets, also called gas giants. They are much more massive than the terrestrial planets, and do not have a solid surface. Jupiter is the largest of all the planets with a diameter of about 12, and mass over 300 times that of the Earth! The Jovian planets do not have a solid surface – the vast majority of their mass being in gaseous form (although they may have rocky or metallic cores). Because of this, they have an average density which is much less than the terrestrial planets. Saturn’s mean density is only about 0.7 g/ cm3 – it would float in water! New Moon Waxing Crescent First Quarter Waxing Gibbous Full Moon Waning Gibbous Last Quarter Waning Crescent The moon’s disc is fully in shadow, or there is just a slither of illuminated surface on the edge. Less than half the disc is illuminated, but more is illuminated each night. Approximately half the disc is illuminated, and increasing each night. More than half of the disc is illuminated, and still increasing each night. The whole disc of the moon is illuminated. More than half of the disc is illuminated, but the amount gets smaller each night. Approximately half the disc is illuminated, but this gets less each night. Less than half the disc of the moon is illuminated, and this gets less each night. Table 18.3: Lunar Phases 18.5 The Minor Bodies 215 Figure 18.4: The Planets 18.5 The Minor Bodies As well as the Major Planets, the solar system also contains innumerable smaller bodies in orbit around the Sun. These are generally the dwarf planets (Ceres, Pluto, Eris), the other minor planets, also known as planetoids or asteroids, and comets. 18.5.1 Asteroids Asteroids are celestial bodies orbiting the Sun in more or less regular orbits mostly between Mars and Jupiter. They are generally rocky bodies like the inner (terrestrial) planets, but of much smaller size. They are countless in number ranging in size from about ten meters to hundreds of kilometres. 18.5.2 Comets A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail. Most comets have a very eccentric orbit (featuring a highly flattened ellipse, or even a parabolic track), and as such spend most of their time a very long way from the Sun. Comets are composed of rock, dust and ices. When they come close to the Sun, the heat evaporates the ices, causing a gaseous release. This gas and loose material which comes away from the body of the comet is swept away from the Sun by the Solar wind, forming the tail. Most larger comets exhibit two kinds of tail: a straight gas tail (often blue-green in photographs), and a wider, occasionally curved dust tail (reflecting whitish sunlight). Comets whose orbit brings them close to the Sun more frequently than every 200 years are considered to be short period comets, the most famous of which is probably Comet Halley, named after the British astronomer E DMUND H ALLEY (1656–1741/423 ), which has an orbital period of roughly 76 years. 3 Halley lived in a time when Great Britain still used the Julian calendar and started the years in March. He died January 14th, 1741 (Julian), which was called January 25th 1742 (Gregorian) in most other European countries. 216 18.6 Chapter 18. Astronomical Phenomena Meteoroids These objects are small pieces of space debris left over from the early days of the solar system or which crumbled off a comet when it came close to the sun. These particles orbit the Sun and come in a variety of shapes, sizes an compositions, ranging from microscopic dust particles up to about ten meters across. Sometimes these objects collide with the Earth. The closing speed of these collisions is generally extremely high (tens of kilometres per second). When such an object ploughs through the Earth’s atmosphere, a large amount of kinetic energy is converted into heat and light, and a visible flash or streak can often be seen with the naked eye. Even the smallest particles can cause these events which are commonly known as shooting stars. While smaller objects tend to burn up in the atmosphere, larger, denser objects can penetrate the atmosphere and strike the surface of the planet, sometimes leaving meteor craters. Sometimes the angle of the collision means that larger objects pass through the atmosphere but do not strike the Earth. When this happens, spectacular fireballs are sometimes seen. To clarify some terminology: Meteoroids are the objects when they are floating in space. Meteor is the name given to the visible atmospheric phenomenon. Shooting Star colloquial term for a small meteor Fireball, Bolide term for a very bright meteor. These illuminate the landscape, sometimes for several seconds, and occasionally even cause sounds. These are also candidates for Meteorites , the objects that penetrate the atmosphere and land (or impact) on the surface. In some nights over the year you can observe increased meteorite activity. Those meteors seem to come from a certain point in the sky, the Radiant. But what we see is similar to driving through a mosquito swarm which all seem to come head-on. Earth itself moves through space, and sweeps up a dense cloud of particles which originates from a comet’s tail. Stellarium’s Meteor Shower plugin (see section 13.6) can help you planning your next meteor observing night. 18.7 Zodiacal Light and Gegenschein In very clear nights on the best observing sites, far away from the light pollution of our cities, you can observe a feeble glow also known as “false twilight” after evening twilight in the west, or before dawn in the east. The glow looks like a wedge of light along the ecliptic. Exactly opposite the sun, there is another dim glow that can be observed with dark-adapted eyes in perfect skies: the Gegenschein (counterglow). This is sunlight reflected off the same dust and meteoroids in the plane of our solar system which is the source of meteors. Stellarium’s sky can show the Zodiacal light (Kwon, Hong, and Weinberg, 2004), but observe how quickly light pollution kills its visibility! 18.8 The Milky Way There is a band of very dense stars running right round the sky in huge irregular stripe. Most of these stars are very dim, but the overall effect is that on very dark clear nights we can see a large, beautiful area of diffuse light in the sky. It is this for which we name our galaxy the Milky Way. The reason for this effect is that our galaxy is somewhat like a disc, and we are off to one side. Thus when we look towards the centre of the disc, we see more a great concentration of stars (there are more star in that direction). As we look out away from the centre of the disc we see fewer stars we are staring out into the void between galaxies! It’s a little hard to work out what our galaxy would look like from far away, because when we look up at the night sky, we are seeing it from the inside. All the stars we can see are part of the 18.9 Nebulae 217 Milky Way, and we can see them in every direction. However, there is some structure. There is a higher density of stars in particular places. 18.9 Nebulae Seen with the naked eye, binoculars or a small telescope, a nebula (plural nebulae) is a fuzzy patch on the sky. Historically, the term referred to any extended object, but the modern definition excludes some types of object such as galaxies. Observationally, nebulae are popular objects for amateur astronomers – they exhibit complex structure, spectacular colours (in most cases only visible in color photography) and a wide variety of forms. Many nebulae are bright enough to be seen using good binoculars or small to medium sized telescopes, and are a very photogenic subject for astro-photographers. Nebulae are associated with a variety of phenomena, some being clouds of interstellar dust and gas in the process of collapsing under gravity, some being envelopes of gas thrown off during a supernova event (so called supernova remnants), yet others being the remnants of dumped outer layers around dying stars (planetary nebulae). Examples of nebulae for which Stellarium has images include the Crab Nebula (M1), which is a supernova remnant, and the Dumbbell Nebula (M27) and the Ring Nebula (M57) which are planetary nebulae. 18.9.1 The Messier Objects The Messier objects are a set of astronomical objects catalogued by C HARLES M ESSIER (1730– 1817) in his catalogue of Nebulae and Star Clusters first published in 1774. The original motivation behind the catalogue was that Messier was a comet hunter, and he was frustrated by objects which resembled but were not comets. He therefore compiled a list of these annoying objects. The first edition covered 45 objects numbered M1 to M45. The total list consists of 110 objects, ranging from M1 to M110. The final catalogue was published in 1781 and printed in the Connaissance des Temps in 1784. Many of these objects are still known by their Messier number. Because the Messier list was compiled by astronomers in the Northern Hemisphere, it contains only objects from the north celestial pole to a celestial latitude of about −35◦ . Many impressive Southern objects, such as the Large and Small Magellanic Clouds are excluded from the list. Because all of the Messier objects are visible with binoculars or small telescopes (under favourable conditions), they are popular viewing objects for amateur astronomers. In early spring, astronomers sometimes gather for “Messier Marathons”, when all of the objects can be viewed over a single night. Stellarium includes images of many Messier objects. 18.10 Galaxies Stars, it seems, are gregarious – they like to live together in groups. These groups are called galaxies. The number of stars in a typical galaxy is literally astronomical – many billions – sometimes over hundreds of billions of stars! Our own star, the sun, is part of a galaxy. When we look up at the night sky, all the stars we can see are in the same galaxy. We call our own galaxy the Milky Way (or sometimes simply “the Galaxy”4 ). Other galaxies appear in the sky as dim fuzzy blobs. Only four are normally visible to the naked eye. The Andromeda galaxy (M31) visible in the Northern hemisphere, the two Magellanic 4 Which means closely the same thing, the word deriving from Greek gala=milk. 218 Chapter 18. Astronomical Phenomena clouds, visible in the Southern hemisphere, and the home galaxy Milky Way, visible in parts from north and south under dark skies. There are thought to be billions of galaxies in the universe comprised of an unimaginably large number of stars. The vast majority of galaxies are so far away that they are very dim, and cannot be seen without large telescopes, but there are dozens of galaxies which may be observed in medium to large sized amateur instruments. Stellarium includes images of many galaxies, including the Andromeda galaxy (M31), the Pinwheel Galaxy (M101), the Sombrero Galaxy (M104) and many others. Astronomers classify galaxies according to their appearance. Some classifications include spiral galaxies, elliptical galaxies, lenticular galaxies and irregular galaxies. 18.11 Eclipses Eclipses occur when an apparently large celestial body (planet, moon etc.) moves between the observer (that’s you!) and a more distant object – the more distant object being eclipsed by the nearer one. 18.11.1 Solar Eclipses Solar eclipses occur when our Moon moves between the Earth and the Sun. This happens when the inclined orbit of the Moon causes its path to cross our line of sight to the Sun. In essence it is the observer falling under the shadow of the moon. There are three types of solar eclipses: Partial The Moon only covers part of the Sun’s surface. Total The Moon completely obscures the Sun’s surface. Annular The Moon is at apogee (furthest from Earth in its elliptic orbit) and its disc is too small to completely cover the Sun. In this case most of the Sun’s disc is obscured – all except a thin ring around the edge. 18.11.2 Lunar Eclipses Lunar eclipses occur when the Earth moves between the Sun and the Moon, and the Moon is in the Earth’s shadow. They occur under the same basic conditions as the solar eclipse but can occur more often because the Earth’s shadow is so much larger than the Moon’s. Total lunar eclipses are more noticeable than partial eclipses because the Moon moves fully into the Earth’s shadow and there is very noticeable darkening. However, the Earth’s atmosphere refracts light (bends it) in such a way that some sunlight can still fall on the Moon’s surface even during total eclipses. The blue parts of sunlight are scattered and filtered away, so that there is a marked reddening of the light as it passes through the atmosphere, and this makes the Moon appear in a deep red colour. The darkness and colors are notably influenced by atmospheric clarity and clouds. After big volcanic eruptions eclipses are often reported darker. 18.12 Observing Hints When stargazing, there’s a few little things which make a lot of difference, and are worth taking into account. Dark skies For many people getting away from light pollution isn’t an easy thing. At best it means a drive away from the towns, and for many the only chance to see a sky without significant glow from street lighting is on vacation. If you can’t get away from the cities easily, make the most of it when you are away. 18.13 Atmospheric effects 219 Wrap up warm The best observing conditions are the same conditions that make for cold nights, even in the summer time. Observing is not a strenuous physical activity, so you will feel the cold a lot more than if you were walking around. Wear a lot of warm clothing, don’t sit/lie on the floor (at least use a camping mat, consider taking a deck-chair), and take a flask of hot drink. Dark adaptation The true majesty of the night sky only becomes apparent when the eye has had time to become accustomed to the dark. This process, known as dark adaptation, can take up to half an hour, and as soon as the observer sees a bright light they must start the process over. Red light doesn’t compromise dark adaptation as much as white light, so use a red torch if possible (and one that is as dim as you can manage with). A dim single red LED light is ideal, also to have enough light to take notes. The Moon Unless you’re particularly interested in observing the Moon on a given night, it can be a nuisance—it can be so bright as to make observation of dimmer objects such as nebulae impossible. When planning what you want to observe, take the phase and position of the Moon into account. Of course Stellarium is the ideal tool for finding this out! Averted vision A curious fact about the eye is that it is more sensitive to dim light towards the edge of the field of view. If an object is slightly too dim to see directly, looking slightly off to the side but concentrating on the object’s location can often reveal it. Angular distance Learn how to estimate angular distances. Learn the angular distances described in section 17.5.2. If you have a pair of binoculars, find out the angular distance across the field of view and use this as a standard measure. 18.13 Atmospheric effects 18.13.1 Atmospheric Extinction Atmospheric Extinction is the attenuation of light of a celestial body by Earth’s atmosphere. In the last split-second of its travel into our eyes or detectors, light from outer space has to pass our atmosphere, through layers of mixed gas, water vapour and dust. If a star is in the zenith, its light must pass one air mass and is reduced by whatever amount of water and dust is above you. When the star is on the horizon, it has to pass about 40 times longer through the atmosphere: 40 air masses (Fig. 18.5). The number of air masses increases fast in low altitudes, this is why we see so few stars along the horizon. Usually blue light is extinguished more, this is why the sun and moon (and brigher stars) appear reddish on the horizon. Stellarium can simulate extinction, and you can set the opacity of your atmosphere with a global factor k, the magnitude loss per airmass (see section 4.4.1). The best mountaintop sites may have k = 0.15, while k = 0.25 seems a value usable for good locations in lower altitudes. 18.13.2 Atmospheric Refraction Atmospheric Refraction is a lifting effect of our atmosphere which can be observed by the fact that objects close to the horizon appear higher than they should be if computed only with spherical trigonometry. Stellarium simulates refraction for terrestrial locations when the atmosphere is switched on. Refraction depends on air pressure and temperature. Figure 18.6 has been created from the same formulae that are employed in Stellarium. You can see how fast refraction grows very close to the mathematical horizon. Note that these models can only give approximate conditions. There are many weird effects in the real atmosphere, when temperature inversion layers can create light ducts, double sunsets etc. Also note that the models give meaningful results only for altitudes above approximately −2◦ . Below that, in nature, there is always ground which blocks our view. In Stellarium you can switch off the ground, and you can observe a sunset with a strange egg-shaped sun below the horizon. This Chapter 18. Astronomical Phenomena 220 Airmass, Absorption and Extinction Angle (m_z=6.5; apparent altitudes) 15° 0 10 20 30 40 0 1 2 3 4 Airmass Absorption [Dmag] k_v 0.4 0.3 0.25 0.2 0.175 0.15 0.125 10° Star invisible at k_v 0.4 0.3 0.25 0.2 0.175 0.15 0.125 5° 0° −2 −1 (Model: Schaefer, S&T4/1987; Airmass: Rozenberg 1966; Observations: Müller 1970) 5 mag = 6 © Georg Zotti 2009−2010, ASTROSIM Figure 18.5: Airmass and Extinction. The figure shows Airmass (blue) along the line of sight in the altitude labeled on the left side. The green curves show how many magnitudes an object is dimmed down, depending on extinction factor k (called kv in the figure). The red curves indicate at which altitude a star of given magnitude can be seen with good eyesight, again depending on k. The black dots are observed values found in the literature. is of course nonsense. Stellarium is also not able to properly recreate the atmospheric distortions as seen from a stratosphere balloon, where the height of earth’s surface is several degrees below the mathematical horizon. Scintillation Scintillation is the scientific name of the twinkling which stars show in turbulent atmosphere. The twinkling is caused by moving pockets of air with different temperature. Observe a star low on the horizon with a telescope, and you will note it does not stand still but dances around a bit, often also changing color to show red or blue hues. While the twinkling of stars may look fine and comforting to the naked eye on a nice warm summer evening, telescopic observers and astrophotographers don’t like it at all. They rather complain about “bad seeing”, because it deteriorates the optical resolution of their instruments and photographs. Just like extinction and refraction are stronger along the horizon, stars in low altitude in general show more twinkling than stars higher up in the sky. Note that planets seem to be affected less by scintillation: they are not point sources, but little disks, and so the effect of the turbulent pockets of air distorting different parts of the disks cancels out a bit when observing with the naked eye: planets appear to be more stable. Of course, the view −1.1° −1.0° −0.9° −0.8° −0.7° −0.6° −0.5° Bennett’s Formula Correction of observed altitudes Pressure: −500..100..1100 mbar Temperature: −60..10..50°C 1013.25 mbar, 10°C −0.4° −0.3° −0.2° −0.1° 0.0° 0.1° 0.2° 0.3° 0.4° 0.5° Sæmundsson’s Formula Correction of geometric altitudes 0.6° 0.7° 0.8° 0.9° Dalt © Georg Zotti 2010, ASTROSIM Figure 18.6: Refraction. The figure shows corrective values (degrees) which are subtracted from observed altitudes (left side) to reach geometric altitudes, or values to be added to computed values (right side). The models used are not directly inverse operations. (Model: Meeus, Astr.Alg.1994) −1.2° Refraction −10° −1.3° −5° 0° 5° 10° 15° 20° 25° 18.13 Atmospheric effects 221 222 Chapter 18. Astronomical Phenomena in a telescope will still be deteriorated by the turbulent atmosphere. While bad seeing was one key motivation of sending telescopes into earth orbit since the 1970s, the latest generation of ground-based giant telescopes is able to compensate for the turbulent motion by rapidly deforming their secondary mirror. 18.13.3 Light Pollution An ugly side effect of civilisation is a steady increase in outdoor illumination. Many people think it increases safety, but while this statement can be questioned, one definite result, aside from environmental issues like dangers for the nocturnal fauna, are ever worsening conditions for astronomical observations or just enjoyment of the night sky. Stellarium can simulate the effect of light pollution on the visibility of celestial objects. This is controlled from the light pollution section of the Sky tab of the View window (see section 4.9). Light pollution levels are set using a numerical value between 1 and 9 which corresponds to the Bortle Dark Sky Scale (see Appendix B). Given that public lighting became bright enough to cause adverse effects on observability only during the 19th century, Stellarium presents an unpolluted sky for dates before 1825. Note that of course light pollution was not switched on over night, but became gradually noticeable over decades, but you have to estimate the appropriate level. In addition, local variations of the amount of light pollution can be included in a light pollution layer in the landscapes, see section 7 for details. This foreground layer may include all kinds of light, e.g. campfires, so this is also available for earlier dates. 19. A Little Sky Guide PAUL ROBINSON , WITH ADDITIONS BY A LEXANDER W OLF This chapter lists some astronomical objects that can be located using Stellarium. All of them can be seen with the naked eye or binoculars. Since many astronomical objects have more than one name (often having a “proper name”, a “common name” and various catalogue numbers), the chapter lists the name as it appears in Stellarium — use this name when using Stellarium’s search function — and any other commonly used names. The Location Guide entry gives brief instructions for finding each object using nearby bright stars or groups of stars when looking at the real sky — a little time spent learning the major constellations visible from your latitude will pay dividends when it comes to locating fainter (and more interesting!) objects. When trying to locate these objects in the night sky, keep in mind that Stellarium displays many stars that are too faint to be visible without optical aid, and even bright stars can be dimmed by poor atmospheric conditions and light pollution. 19.1 Dubhe and Merak, The Pointers Type: Stars Magnitude: 1.83, 2.36 Location Guide: The two “rightmost” of the seven stars that form the main shape of “The Plough” (or “Big Dipper”, part of Ursa Major). Northern hemisphere observers are very fortunate to have two stars that point towards Polaris which lie very close to the northern celestial pole. Whatever the time of night or season of the year they are always an immediate clue to the location of Polaris, the Pole Star. 19.2 M31, Messier 31, The Andromeda Galaxy Type: Spiral Galaxy Magnitude: 3.4 224 Chapter 19. A Little Sky Guide Location Guide: Find the three bright stars that constitute the main part of the constellation of Andromeda. From the middle of these look toward the constellation of Cassiopeia. M31 is the most distant object visible to the naked eye, and among the few nebulae that can be seen without a telescope or powerful binoculars. Under good conditions it appears as a large fuzzy patch of light. It is a galaxy containing billions of stars whose distance is roughly 2.5 million light years from Earth. 19.3 The Garnet Star, µ Cephei Type: Variable Star Magnitude: 4.25 (Avg.) Location Guide: Cephius lies “above” the W-shape of Cassiopeia. The Garnet Star lies slightly to one side of a point halfway between 5 Cephei and 21 Cephei. A “supergiant” (1035 Solar radii) of spectral class M with a strong red colour. Given its name by Sir William Herschel in the 18th century, the colour is striking in comparison to its blue-white neighbours. 19.4 4 and 5 Lyrae, ε Lyrae Type: Double Star Magnitude: 4.7 Location Guide: Close to Vega (α Lyrae), one of the brightest stars in the sky. In binoculars ε Lyrae is resolved into two separate stars. Remarkably, each of these is also a double star (although this will only be seen with a telescope) and all four stars form a physical system. 19.5 M13, Hercules Cluster Type: Globular Cluster Magnitude: 5.8 Location Guide: Located approximately 1/3 of the way along a line from 44 (η) to 40 (ζ ) Herculis. This cluster of hundreds of thousands of mature stars appears as a circular “cloud” using the naked eye or binoculars (a large telescope is required to resolve individual stars). Oddly the cluster appears to contain one young star and several areas that are almost devoid of stars. 19.6 M45, The Pleiades, The Seven Sisters Type: Open Cluster Magnitude: 1.2 (Avg.) Location Guide: Lies on the Bull’s back, about 1/3 between Aldebaran in Taurus and Almaak in Andromeda. Depending upon conditions, six to 9 of the blueish stars in this famous cluster will be visible to someone with average eyesight, and in binoculars it is a glorious sight. The cluster has more than 500 members in total, many of which are shown to be surrounded by nebulous material in long exposure photographs. 19.7 Algol, The Demon Star, β Persei 19.7 225 Algol, The Demon Star, β Persei Type: Variable Star Magnitude: 3.0 (Avg.) Location Guide: Halfway between Aldebaran in Taurus and the middle star of the “W” of Cassiopeia. Once every three days or so, Algol’s brightness changes from 2.1 to 3.4 and back within a matter of hours. The reason for this change is that Algol has a dimmer giant companion star, with an orbital period of about 2.8 days, that causes a regular partial eclipse. Although Algol’s fluctuations in magnitude have been known since at least the 17th century, it was the first to be proved to be due to an eclipsing companion — it is therefore the prototype Eclipsing Variable. 19.8 Sirius, α Canis Majoris Type: Star Magnitude: -1.47 Location Guide: Sirius is easily found by following the line of three stars in Orion’s belt southwards. Sirius is a white dwarf star at a comparatively close 8.6 light years. This proximity and its high innate luminance makes it the brightest star in our sky. Sirius is a double star; its companion is a White Dwarf, much dimmer but very hot, and is believed to be smaller than the earth. 19.9 M44, The Beehive, Praesepe Type: Open Cluster Magnitude: 3.7 Location Guide: Cancer lies about halfway between the twins (Castor & Pollux) in Gemini and Regulus, the brightest star in Leo. The Beehive can be found between Asellus Borealis and Asellus Australis. There are probably 350 or so stars in this cluster, although it appears to the naked eye simply as a misty patch. It contains a mixture of stars from red giants to white dwarf and is estimated to be some 700 million years old. 19.10 27 Cephei, δ Cephei Type: Variable Star Magnitude: 4.0 (Avg.) Location Guide: Locate the four stars that form the square of Cepheus. One corner of the square has two other bright stars nearby forming a distinctive triangle — δ is at the head of this triangle in the direction of Cassiopeia. δ Cephei gives its name to a whole class of variables, all of which are pulsating high-mass stars in the later stages of their evolution. δ Cephei is also a double star with a companion of magnitude 6.3 visible in binoculars. 19.11 M42, The Great Orion Nebula Type: Nebula Magnitude: 4.0 Location Guide: Almost in the middle of the area bounded by Orion’s belt and lower stars, Saiph and Rigel. 226 Chapter 19. A Little Sky Guide The Great Orion Nebula is the brightest nebula visible in the night sky and lies at about 1.500 light years from earth. It is a truly gigantic gas and dust cloud that extends for several hundred light years, reaching almost halfway across the constellation of Orion. The nebula contains a cluster of hot young stars known as the Trapezium, and more stars are believed to be forming within the cloud. 19.12 La Superba, Y Canum Venaticorum, HIP 62223 Type: Star Magnitude: 5.4 (Avg.) Location Guide: Almost the center of the arch of stars of Ursa Major’s tail. Forms a neat triangle with Phekda (γ) and Alkaid (η, tail tip) in Ursa Major towards Canes Venatici. La Superba (215 Solar radii) is a “Carbon Star” — a group of relatively cool gigantic (usually variable) stars that have an outer shell containing high levels of carbon. This shell is very efficient at absorbing short wavelength blue light, giving carbon stars a distinctive red or orange tint. One of the coolest and reddest known stars. 19.13 52 and 53 Bootis, ν 1 and ν 2 Bootis Type: Double Star Magnitude: 5.0, 5.0 Location Guide: Follow a line from Seginus (γ Boo, left shoulder) to Nekkar (β Boo, the head) and then continue for the same distance again to arrive at this double star. This optical double star consists of a pair of different spectral type, and 52 Bootis, at approximately 800 light years, is twice as far away as 53. 19.14 PZ Cas, HIP 117078 Type: Variable Star Magnitude: 8.2 (Avg.) Location Guide: Lies about 1/3 between Caph (β Cas, the top right star of “W”) in Cassiopeia and ι Cephei (32 Cep, top left star in “rectangle” of Cepheus). This faint red star is one of the biggest known stars — its average size parameter is 1565 Solar radii (the true value is from 1340 to 1940 Solar radii). PZ Cas is a pulsating variable star located in a region with heavy dust extinction. 19.15 VV Cephei, HIP 108317 Type: Variable Star, Double Star Magnitude: 5.1 (Avg.) Location Guide: Lies near the center of the “rectangle” of Cepheus). This is an interesting eclipsing binary system — VV Cep A (1457 Solar radii) is a highly distorted star in a binary system, losing mass to its B-type companion VV Cephei B (10 Solar radii) for at least part of its orbit. 19.16 AH Scorpii, HIP 84071 Type: Variable Star Magnitude: 7.1 (Avg.) 19.17 Albireo, β Cygni 227 Location Guide: Lies in Scorpius, about 1 41 of a continuation of the Scorpion’s “tail”. AH Sco (1411 Solar radii) is variable by nearly 3 magnitudes in the visual range, and an estimated 20% in total luminosity. The variation in diameter is not clear because the temperature also varies. 19.17 Albireo, β Cygni Type: Double Star Magnitude: 3.4, 5.1 Location Guide: The “head” of Cygni. When viewed with the naked eye, it appears to be a single star. However, in a telescope it readily resolves into a double star, consisting of Albireo A (amber), and Albireo B (blue-green). Separated by 3500 , the two components provide one of the best contrasting double stars in the sky due to their different colors. Figure 19.1: Albireo: A Bright and Beautiful Double. Credit & Copyright: Richard Yandrick. 19.18 31 and 32 Cygni, o1 and o2 Cygni Type: Multiple Star Magnitude: 3.8, 4.0 Location Guide: The two bright stars about 1/2 between Deneb (α Cygni, “tail” of Cygnus) and Rukh (δ Cygni, middle of the left “wing” of Cygnus). The wide binary o1 Cygni and o2 Cygni is separated 610 (NNE), and this star is an easy nakedeye double. o1 Cygni with 30 Cyg and HD 192579 (HIP 99676) is a moderately difficult triple system. And surprise — each of o1 Cyg and o2 Cyg are also Algol-type eclipsing binaries! 19.19 The Coathanger, Brocchi’s Cluster, Cr 399 Type: Asterism Location Guide: It is best found by slowly sweeping across the Milky Way along an imaginary line from the bright star Altair toward the even brighter star Vega (around 1/3 between Altair and Vega). 228 Chapter 19. A Little Sky Guide The asterism is made up of 10 stars ranging from 5th to 7th magnitude which form the conspicuous “coathanger”, a straight line of 6 stars with a “hook” of 4 stars on the south side. Under a dark sky, Collinder 399 can be seen with the naked eye as an unresolved patch of light; binoculars or a telescope at very low power are usually needed in order to view the “coathanger” asterism. 19.20 Kemble’s Cascade Type: Asterism Location Guide: The asterism lies in the constellation Camelopardalis, about 1/3 between CS Cam and α Cam — HIP 18505 has magnitude 5 and can be found in the center of the chain. Kemble’s Cascade is a chain of stars which are visible in binocular even in light-polluted skies. 19.21 The Double Cluster, χ and h Persei, NGC 884 and NGC 869 Type: Open Clusters Location Guide: The two open clusters near stars χ and h in the constellation Perseus. The Double Cluster (also known as Caldwell 14 or C14) is the common name for the naked-eye open clusters NGC 869 and NGC 884 (often designated h Persei and χ Persei, respectively). The Double Cluster is approximately the radiant of the Perseid meteor shower, which peaks annually around August 12 or 13. Although easy to locate in the northern sky, observing the Double Cluster in its two parts requires optical aid. They are described as being an “awe-inspiring” and “breathtaking” sight, and are often cited as targets in astronomical observers’ guides. 19.22 Large Magellanic Cloud, PGC 17223 Type: Dwarf Spiral Galaxy Magnitude: 0.9 Location Guide: It is visible as a faint “cloud” in the night sky of the southern hemisphere straddling the border between the constellations of Dorado and Mensa, and it appears from Earth more than 20 times the width of the full moon. The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way. The Large Magellanic Cloud is usually considered an irregular galaxy. However, it shows signs of a bar structure, and has more recently been reclassified as a Magellanic-type dwarf spiral galaxy. At a distance of 50 kiloparsecs, the LMC is the third closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (~16 kiloparsecs) and the putative Canis Major Dwarf Galaxy (~12.9 kiloparsecs, though its status as a galaxy is under dispute) lying closer to the center of the Milky Way. The LMC has a diameter of about 14,000 light-years (~4.3 kpc) and a mass of approximately 10 billion (1010 ) solar masses, making it roughly 1/100 as massive as the Milky Way. The LMC has a wide range of galactic objects and phenomena — surveys of the galaxy have found roughly 60 globular clusters, 400 planetary nebulae, and 700 open clusters, along with hundreds of thousands of giant and supergiant stars. 19.23 Tarantula Nebula, C 103, NGC 2070 Type: Nebula Magnitude: 7.3 Location Guide: Part of Large Magellanic Cloud. The Tarantula Nebula (also known as 30 Doradus) is an H II region in the Large Magellanic Cloud (LMC). 30 Doradus has at its centre the star cluster NGC 2070 which includes the compact 19.24 Small Magellanic Cloud, NGC 292, PGC 3085 229 Figure 19.2: Small and Large Magellanic Clouds over Paranal Observatory. Credit: ESO/J. Colosimo. concentration of stars known as R136 that produces most of the energy that makes the nebula visible. The estimated mass of the cluster is 450,000 solar masses, suggesting it will likely become a globular cluster in the future (Bosch, E. Terlevich, and R. Terlevich, 2009). The closest supernova observed since the invention of the telescope, Supernova 1987A, occurred in the outskirts of the Tarantula Nebula. 19.24 Small Magellanic Cloud, NGC 292, PGC 3085 Type: Dwarf Irregular Galaxy Magnitude: 2.2 Location Guide: It is located mostly in the constellation of Tucana and appears as a hazy, light patch in the night sky about 3◦ across, looking like a detached piece of the Milky Way. Since it has a very low surface brightness, it is best viewed from a dark site away from city lights. The Small Magellanic Cloud (SMC) is a dwarf galaxy near the Milky Way. It is classified as a dwarf irregular galaxy. It has a diameter of about 7,000 light-years and has a total mass of approximately 7 billion times the mass of the Sun. The SMC contains a central bar structure and it is speculated that it was once a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular. At a distance of about 200,000 light-years, it is one of the Milky Way’s nearest neighbors. It is also one of the most distant objects that can be seen with the naked eye. 19.25 ω Centauri cluster, C 80, NGC 5139 Type: Globular Cluster Magnitude: 5.3 Location Guide: It is located around 1/3 between ζ and γ Centauri. Omega Centauri (ω Cen), or NGC 5139, is a globular cluster in the constellation of Centaurus that was first identified as a non-stellar object by Edmond Halley in 1677. Located at a distance 230 Chapter 19. A Little Sky Guide of 15,800 light-years (4,850 pc), it is the largest globular cluster in the Milky Way at a diameter of roughly 150 light-years. It is estimated to contain approximately 10 million stars and a total mass equivalent to 4 million solar masses. Omega Centauri is so distinctive from the other galactic globular clusters that it is thought to have an alternate origin as the core remnant of a disrupted dwarf galaxy (Noyola, Gebhardt, and Bergmann, 2008). 19.26 47 Tucanae, C 106, NGC 104 Type: Globular Cluster Magnitude: 4.1 Location Guide: It can be seen with the naked eye near Small Magellanic Cloud. It is the one of brightest globular cluster in the sky, and is noted for having a very bright and dense core. It is also one of the most massive globular clusters in the Milky Way Galaxy, containing millions of stars. The cluster appears roughly the size of the full moon in the sky under ideal conditions. 19.27 The Coalsack Nebula, C 99 Type: Dark Nebula Location Guide: Dark region between α and β Crux. The Coalsack Nebula is the most prominent dark nebula in the skies, easily visible to the naked eye as a dark patch silhouetted against the southern Milky Way. It is located at a distance of approximately 600 light years away from Earth. The Coalsack is important in Australian Aboriginal astronomy, and forms the head of the Emu in the sky in several Aboriginal cultures. 19.28 Mira, o Ceti, 68 Cet Type: Variable Star Magnitude: 2.0–10.1 Location Guide: It is located around 1/3 between δ and θ Ceti. Mira (o Ceti) is a star estimated 200–400 light years away in the constellation Cetus. Mira is a binary star system that consists of a red giant (Mira A) undergoing mass loss and a high temperature white dwarf companion (Mira B) that is accreting mass from the primary. Such an arrangement of stars is known as a symbiotic system, and this is the closest such symbiotic pair to the Sun. Mira is the brightest periodic variable in the sky that is not visible to the naked eye for part of its cycle. Its distance is uncertain. Mira A is a well-known example of a category of long-period variable stars known as Mira variables, which are named after it. 19.29 α Persei Cluster, Cr 39, Mel 20 Type: Open Cluster Magnitude: 1.2 Location Guide: Around the white-yellow supergiant Mirfak, also known as α Persei in direction to δ Persei. The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster in the constellation of Perseus. To the naked eye, the cluster consists of several blue (spectral class B) stars. 19.30 M7, The Ptolemy Cluster 231 Figure 19.3: The Coalsack Nebula taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope. Credit: ESO. 19.30 M7, The Ptolemy Cluster Type: Open Cluster Magnitude: 3.3 Location Guide: The cluster is easily detectable with the naked eye, close to the “sting” of Scorpius — near the center of the line between Shaula (λ Scorpii) and Kaus Media (δ Sagittarii). M7 has been known since antiquity — it was first recorded by the 2nd-century Greek-Roman astronomer Ptolemy, who described it as a nebula in 130 AD. Telescopic observations of the cluster reveal about 80 stars within a field of view of 1.3◦ across. At the cluster’s estimated distance of 980 light years this corresponds to an actual diameter of 25 light years. 19.31 M24, The Sagittarius Star Cloud Type: Star Cloud Magnitude: 4.6 Location Guide: In the Milky Way region near Polis (µ Sagittarii). The Sagittarius Star Cloud is a star cloud in the constellation of Sagittarius, approximately 600 light years wide. The stars, clusters and other objects comprising M24 are part of the Sagittarius or Sagittarius-Carina arms of the Milky Way galaxy. Messier described M24 as a “large nebulosity containing many stars” and gave its dimensions as being some 1.5◦ across. 232 19.32 Chapter 19. A Little Sky Guide IC 4665, The Summer Beehive Cluster Type: Open Cluster Magnitude: 4.2 Location Guide: Visible to the naked eye near Cebalrai (β Ophiuchi). IC 4665 is an open cluster in the constellation Ophiuchus which is easily visible in the smallest of telescopes and also with binoculars. From a sufficiently dark place it is also visible to the naked eye. 19.33 The E Nebula, Barnard 142 and 143 Type: Dark Nebula Location Guide: A well-defined dark area on a background of Milky Way near Tarazed (γ Aquilae). The “E” or “Barnard’s E” Nebula (officially designated as B142 and B143) is a pair of dark nebulae in the constellation Aquila. It is a well-defined dark area on a background of the Milky Way. The size of the nebula is roughly 0.5◦ , and its distance from earth is estimated at about 2000 light years. 20. Exercises PAUL ROBINSON , WITH ADDITIONS BY A LEXANDER W OLF 20.1 Find M31 in Binoculars M31 – the Andromeda Galaxy – is the most distant object visible to the naked eye. Finding it in binoculars is a rewarding experience for new-comers to observing. 20.1.1 Simulation 1. Set the location to a mid-Northern latitude if necessary (M31 isn’t always visible for Southern hemisphere observers). The UK is ideal. 2. Find M31 and set the time so that the sky is dark enough to see it. The best time of year for this at Northern latitudes is Autumn/Winter, although there should be a chance to see it at some time of night throughout the year. 3. Set the field of view to 6◦ (or the field of view of your binoculars if they’re different. 6◦ is typical for 7x50 binoculars). 4. Practise finding M31 from the bright stars in Cassiopeia and the constellation of Andromeda. Learn the chain of stars that extends from Andromeda’s central star perpendicular to her body. 20.1.2 For Real This part is not going to be possible for many people. First, you need a good night and a dark sky. In urban areas with a lot of light pollution it’s going to be very hard to see Andromeda. 20.2 Handy Angles As described in section 17.5.2, your hand at arm’s length provides a few useful estimates for angular size. It’s useful to know whether your handy angles are typical, and if not, what they are. Chapter 20. Exercises 234 The method here below is just one way to do it – feel free to use another method of your own construction! Hold your hand at arm’s length with your hand open – the tips of your thumb and little finger as far apart as you can comfortably hold them. Get a friend to measure the distance between your thumb and your eye, we’ll call this D. There is a tendency to over-stretch the arm when someone is measuring it – try to keep the thumb-eye distance as it would be if you were looking at some distant object. Without changing the shape of your hand, measure the distance between the tips of your thumb and little finger. It’s probably easiest to mark their positions on a piece of paper and measure the distance between the marks, we’ll call this d. Using some simple trigonometry, we can estimate the angular distance θ using equation (17.4). Repeat the process for the distance across a closed fist, three fingers and the tip of the little finger. For example, for one author D = 72 cm, d = 21 cm, so:  21 θ = 2 · arctan 144  ≈ 16 1◦ 2 (20.1) Remember that handy angles are not very precise – depending on your posture at a given time the values may vary by a fair bit. 20.3 Find a Lunar Eclipse Stellarium comes with two scripts for finding lunar eclipses, but can you find one on a different date? 20.4 Find a Solar Eclipse Find a Solar Eclipse using Stellarium and take a screenshot of it. Use the location panel and see how the eclipse look on different locations at the same time. Don’t forget to have “Topocentric coordinates” enabled in the settings (see section 17.9.1). 20.5 Find a retrograde motion of Mars Find Mars using Stellarium and take a series of screenshots of its position at different times. Use the date and time panel and see how the motion of Mars changes over the time. Find periods of direct and retrograde motion of Mars (see also section 16.5). 20.6 Analemma Set a time around noon and set time rate to pause, turn on the azimuthal grid. Find the Sun and check its horizontal coordinates. Use the date and time panel and see how the horizontal coordinates of the Sun change over time (please use one time step for simulation — look at the position of the Sun every 7 days for example). Use the location panel and see how the positions of the Sun look from different location at the same times. Check the change of positions of the Sun on Mars at the same times. 20.7 Transit of Venus 20.7 235 Transit of Venus Set date to 6th of June, 2012, find Venus near the Sun and change scale of the view (zoom in). Find time of all four contacts and maximum of transit for your location. Because the Sun appears to rotate as it crosses the sky, Venus will appear to move on some curve — for example it will be an inverted “U” shape for eastern states of Australia. Check difference of path shape of Venus for equatorial and azimuthal mounts. Find a few dates and times for transit of Venus in past and in future. Notice how they usually come in pairs 8 years apart, with gaps of over 100 years between pairs. 20.8 Transit of Mercury Set date to 9th of May, 2016, find Mercury near the Sun and change scale of the view (zoom in). Find time of all four contacts and maximum of transit for your location. Because the Sun appears to rotate as it crosses the sky, Mercury will appear to move on some curve — for example it will be an inverted “U” shape for observers from Europe. Check difference of path shape of Mercury for equatorial and azimuthal mounts. Find few dates and times for transit of Mercury in past and in future. 20.9 Triple shadows on Jupiter Set date to 24th of January, 2015, find Jupiter and change scale of the view (zoom in). Find the time when three shadows will be visible on the disk of Jupiter. Which moons cast those shadows? Check which moons cause triple shadows on Jupiter at 3 June 2014. Details for this phenomenon you can find in the book Mathematical astronomy morsels (Meeus, 1997). 20.10 Jupiter without satellites Set date to 9th November, 2019, find Jupiter and change scale of the view (zoom in). Find time limits for the disappearance of the moons. Which moons are on the back of the planet, and which — in front of it? Please give answer on the same questions for 3 September 2009. Details for this phenomenon you can find in the book Mathematical astronomy morsels (Meeus, 1997) 20.11 Mutual occultations of planets Set date to 13th October, 1590, find Venus and change scale of the view (zoom in). Find time of minimal separation of Venus and Mars on this date. Set typical scale of view for visual observation and check Venus and Mars again. What would the typical observer of that time had said? Find the minimal separation between Venus and Saturn near end of August 1771. What would the typical observer on Earth had said? Find the minimal separation between Mars and Mercury in first half of August 2079. Find mutual occultation of Earth and Mercury as seen from Mars near the end of November 2022. Find mutual occultation of Saturn and Mercury as seen from Venus near the middle of May 1967. Details for this phenomenon you can find in the books More mathematical astronomy morsels (Meeus, 2002) and Mathematical astronomy morsels III (Meeus, 2004) 236 20.12 Chapter 20. Exercises The proper motion of stars Turn off ground and atmosphere, set time rate on pause, find the star HIP 87937 and change the scale of the view to better see Barnard’s Star. Use the date and time panel and see how the location of the star is changing in time (please try use one time step for simulation — look at the position of the star every year for example). When will Barnard’s star cross the border of constellation? When has Barnard’s star crossed the border of constellation in the past? Please check the proper motions of Sirius (HIP 32349), Procyon (HIP 37279), 61 Cyg (HIP 104214) and τ Cet (HIP 8102). Which star has the fastest proper motion? Which star has the slowest rate of proper motion? When will observers see Arcturus and HIP 68706 as close optical binary? Find the minimal angular separation between θ and ε Ind in the past. How will the appearance of following constellations change over a wide range of time (100000..100000 years for example): Ursa Major, Orion, Bootes? A note of caution, however: the proper motions are only modelled by extrapolating their current shift rates in right ascension and declination, but don’t take radial velocity into account. The results in very far times should be seen only as approximations. V Appendices A Default Hotkeys . . . . . . . . . . . . . . . . . . . . . . . . . . 239 B The Bortle Scale of Light Pollution . . . . . . . 247 C Star Catalogues . . . . . . . . . . . . . . . . . . . . . . . . . . 251 D Configuration Files . . . . . . . . . . . . . . . . . . . . . . . 271 E Planetary nomenclature . . . . . . . . . . . . . . . . 299 F Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 G GNU Free Documentation License . . . . . 309 H Acknowledgements . . . . . . . . . . . . . . . . . . . . . 317 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 A. Default Hotkeys The currently configured hotkeys are visible in the Help dialog ( F1 ). Here is the default list for reference. A.1 Mouse actions with combination of the keyboard keys Actions Arrow keys & left mouse drag Page Up/Down & Ctrl + Page Up/Down Ctrl & left mouse drag Ctrl & mouse wheel Ctrl + Shift & mouse wheel Ctrl + Alt & mouse wheel Ctrl + Alt + Shift & mouse wheel Left click Right click Shift & left click Shift & right click Alt + Shift & right click A.2 Description Pan view around the sky Zoom in/out Time dragging Time scrolling: minutes Time scrolling: hours Time scrolling: days Time scrolling: years Select object Clear selection Add custom marker Delete the one closest marker to mouse cursor Delete all custom markers Display Options Shortcut key P Alt + P Ctrl + P Description Planets Planet labels Planet markers Appendix A. Default Hotkeys 240 O Shift + T Ctrl + Shift + P S Alt + S D I Ctrl + Alt + D M Ctrl + Shift + Z G F Shift + G Ctrl + Shift + G A Q , . E Z H ; C V R B Ctrl + Alt + Shift + V Tab Ctrl + Shift + N F11 Ctrl + N Ctrl + Shift + H Ctrl + Shift + V A.3 Planet orbits Planet trails Planet selection marker Stars Stars labels Deep-sky objects (symbols) Deep-sky objects background images Digitized Sky Survey (experimental) Milky Way Zodiacal Light Ground Fog Landscape Illumination Landscape Labels Atmosphere Cardinal points Ecliptic line Equator line Equatorial grid Azimuthal grid Horizon line Meridian line Constellation lines Constellation labels Constellation art Constellation boundaries Select single constellation Remove selection of constellations Native planet names (from starlore) Full-screen mode Night mode Flip scene horizontally Flip scene vertically Miscellaneous Shortcut key Ctrl + C Ctrl + Q Ctrl + S Ctrl + M Ctrl + T Description Copy selected object information to clipboard Quit Save screenshot Switch between equatorial and azimuthal mount Toggle visibility of GUI A.4 Movement and Selection A.4 Movement and Selection Shortcut key Ctrl + H Ctrl + G Shift + E Shift + N Shift + S Shift + W Shift + Z T / \ A.5 241 Description Center on selected object Go to home Set home planet to selected planet (“go there”) Look towards East Look towards North Look towards South Look towards West Look towards Zenith Track object Zoom in on selected object Zoom out Date and Time Shortcut key = Ctrl + = Ctrl + Alt + = Alt + ] [ Ctrl + Alt + Shift + ] Ctrl + Alt + Shift + [ J Shift + J K L Shift + L 7 8 Ctrl + D , P , R D , S Ctrl + D Ctrl + Description Add 1 solar day Subtract 1 solar day Add 1 solar hour Subtract 1 solar hour Add 1 sidereal day Subtract 1 sidereal day Add 7 solar days Subtract 7 solar days Add 1 sidereal year Subtract 1 sidereal year Decrease time speed Decrease time speed (a little) Set normal time rate Increase time speed Increase time speed (a little) Set time rate to zero Set time to now Pause script execution Resume script execution Stop script execution Appendix A. Default Hotkeys 242 A.6 Scripts Shortcut key Ctrl + D 0 Ctrl + D 1 Ctrl + 2 Ctrl + A.7 , , D , D , Description Run script “Solar System Screensaver” Run script “Constellations Tour” Run script “Sky Culture Tour” Run script “Screensaver” 3 Windows Shortcut key F1 Toggle Help window Toggle Configuration window Toggle Search window Toggle Sky and viewing options window Toggle Date/time window Toggle Location window Toggle Shortcuts window Toggle AstroCalc window Toggle Script Console window Toggle Bookmarks window F2 F3 F4 F5 F6 F7 F10 F12 Alt + B A.8 Plugins A.8.1 Angle Measure Description Shortcut key Ctrl + A A.8.2 Description Toggle angle measurement ArchaeoLines Shortcut key Ctrl + U Ctrl + Shift + U A.8.3 Toggle archaeolines Toggle archaeolines dialog Compass Marks Shortcut key Ctrl + Alt + C A.8.4 Description Description Toggle compass marks Equation of Time Shortcut key Ctrl + Alt + T Description Show solution for Equation of Time A.8 Plugins A.8.5 243 Exoplanets Shortcut key Ctrl + Alt + E Alt + E A.8.6 Description Show exoplanets Toggle Exoplanets configuration window Field of View Shortcut key Set FOV to 180◦ Set FOV to 90◦ Set FOV to 60◦ Set FOV to 45◦ Set FOV to 20◦ Set FOV to 10◦ Set FOV to 5◦ Set FOV to 2◦ Set FOV to 1◦ Set FOV to 0.5◦ Ctrl + Alt + 1 Ctrl + Alt + 2 Ctrl + Alt + 3 Ctrl + Alt + 4 Ctrl + Alt + 5 Ctrl + Alt + 6 Ctrl + Alt + 7 Ctrl + Alt + 8 Ctrl + Alt + 9 Ctrl + Alt + 0 A.8.7 Meteor Showers Shortcut key Ctrl + Shift + M Ctrl + Alt + M Ctrl + Alt + Shift + M Oculars Shortcut key Ctrl + O Alt + O Alt + C Ctrl + B A.8.9 Description Toggle meteor showers Toggle radiant labels Show search dialog Show settings dialog Shift + M A.8.8 Description Description Ocular view Oculars popup menu Show crosshairs Telrad sight Pulsars Shortcut key Ctrl + Alt + P Description Show pulsars Appendix A. Default Hotkeys 244 A.8.10 Quasars Shortcut key Ctrl + Alt + Q A.8.11 Description Ctrl + Z Toggle satellite hints Toggle satellite labels Toggle Satellites configuration window Alt + Shift + Z Alt + Z Scenery3d: 3D landscapes Shortcut key Ctrl + W Ctrl + Shift + W Ctrl + Alt + W Ctrl + R Ctrl + R Ctrl + R Ctrl + R Ctrl + R A.8.13 , , , , , T S L D P Description Toggle 3D landscape Show settings dialog Show viewpoint dialog Toggle location text Toggle shadows Toggle torchlight Toggle debug information Reload shaders Solar System Editor Shortcut key Ctrl + Alt + S A.8.14 Show quasars Satellites Shortcut key A.8.12 Description Description Import orbital elements in MPC format... Telescope Control Shortcut key Ctrl + 0 Ctrl + 1 Ctrl + 2 Ctrl + 3 Ctrl + 4 Ctrl + 5 Ctrl + 6 Ctrl + 7 Ctrl + 8 Ctrl + 9 Alt + 1 Alt + 2 Alt + 3 Alt + 4 Alt + 5 Description Move a telescope to a given set of coordinates (shows dialog) Move telescope #1 to selected object Move telescope #2 to selected object Move telescope #3 to selected object Move telescope #4 to selected object Move telescope #5 to selected object Move telescope #6 to selected object Move telescope #7 to selected object Move telescope #8 to selected object Move telescope #9 to selected object Move telescope #1 to the point currently in the center of the screen Move telescope #2 to the point currently in the center of the screen Move telescope #3 to the point currently in the center of the screen Move telescope #4 to the point currently in the center of the screen Move telescope #5 to the point currently in the center of the screen A.8 Plugins Alt + 6 Alt + 7 Alt + 8 Alt + 9 245 Move telescope #6 to the point currently in the center of the screen Move telescope #7 to the point currently in the center of the screen Move telescope #8 to the point currently in the center of the screen Move telescope #9 to the point currently in the center of the screen B. The Bortle Scale of Light Pollution The Bortle scale is a nine-level numeric scale that measures the night sky’s brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution. J OHN E. B ORTLE created the scale and published it in Sky & Telescope magazine (Bortle, 2001) to help amateur astronomers evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies. It gives several criteria for each level beyond naked-eye limiting magnitude (NELM). The accuracy and utility of the scale have been questioned in recent research (Crumey, 2014). B.1 Excellent dark sky site Level: 1 Naked-eye limiting magnitude: 7.6 – 8.0 Approx. SQM mag/arcsec2 : 21.7 – 22.01 Zodiacal light, gegenschein, zodiacal band visible; M33 direct vision naked-eye object; Scorpius and Sagittarius regions of the Milky Way cast obvious shadows on the ground; Airglow is readily visible; Jupiter and Venus affect dark adaptation; surroundings basically invisible. B.2 Typical truly dark site Level: 2 Naked-eye limiting magnitude: 7.1 – 7.5 Approx. SQM mag/arcsec2 : 21.5 – 21.7 Airglow weakly visible near horizon; M33 easily seen with naked eye; highly structured Summer Milky Way; distinctly yellowish zodiacal light bright enough to cast shadows at dusk and dawn; clouds only visible as dark holes; surroundings still only barely visible silhouetted against the sky; many Messier globular clusters still distinct naked-eye objects. 1 Dark Skies Awareness – 248 Appendix B. The Bortle Scale of Light Pollution Figure B.1: Light Pollution Simulation / Bortle Scale B.3 Rural sky Level: 3 Naked-eye limiting magnitude: 6.6 – 7.0 Approx. SQM mag/arcsec2 : 21.3 – 21.5 Some light pollution evident at the horizon; clouds illuminated near horizon, dark overhead; Milky Way still appears complex; M15, M4, M5, M22 distinct naked-eye objects; M33 easily visible with averted vision; zodiacal light striking in spring and autumn, color still visible; nearer surroundings vaguely visible. B.4 Rural/suburban transition Level: 4 Naked-eye limiting magnitude: 6.1 – 6.5 Approx. SQM mag/arcsec2 : 20.4 – 21.3 Light pollution domes visible in various directions over the horizon; zodiacal light is still visible, but not even halfway extending to the zenith at dusk or dawn; Milky Way above the horizon still impressive, but lacks most of the finer details; M33 a difficult averted vision object, only visible when higher than 55◦ ; clouds illuminated in the directions of the light sources, but still dark overhead; surroundings clearly visible, even at a distance. B.5 Suburban sky B.5 249 Suburban sky Level: 5 Naked-eye limiting magnitude: 5.6 – 6.0 Approx. SQM mag/arcsec2 : 19.1 – 20.4 Only hints of zodiacal light are seen on the best nights in autumn and spring; Milky Way is very weak or invisible near the horizon and looks washed out overhead; light sources visible in most, if not all, directions; clouds are noticeably brighter than the sky. B.6 Bright suburban sky Level: 6 Naked-eye limiting magnitude: 5.1 – 5.5 Approx. SQM mag/arcsec2 : 18.0 – 19.1 Zodiacal light is invisible; Milky Way only visible near the zenith; sky within 35◦ from the horizon glows grayish white; clouds anywhere in the sky appear fairly bright; surroundings easily visible; M33 is impossible to see without at least binoculars, M31 is modestly apparent to the unaided eye. B.7 Suburban/urban transition Level: 7 Naked-eye limiting magnitude: 4.6 – 5.0 Approx. SQM mag/arcsec2 : 18.0 – 19.1 Entire sky has a grayish-white hue; strong light sources evident in all directions; Milky Way invisible; M31 and M44 may be glimpsed with the naked eye, but are very indistinct; clouds are brightly lit; even in moderate-sized telescopes the brightest Messier objects are only ghosts of their true selves. B.8 City sky Level: 8 Naked-eye limiting magnitude: 4.1 – 4.5 Approx. SQM mag/arcsec2 : <18.0 Sky glows white or orange — you can easily read; M31 and M44 are barely glimpsed by an experienced observer on good nights; even with telescope, only bright Messier objects can be detected; stars forming familiar constellation patterns may be weak or completely invisible. B.9 Inner-city sky Level: 9 Naked-eye limiting magnitude: 4.0 at best Approx. SQM mag/arcsec2 : <18.0 Sky is brilliantly lit with many stars forming constellations invisible and many weaker constellations invisible; aside from Pleiades, no Messier object is visible to the naked eye; only objects to provide fairly pleasant views are the Moon, the Planets and a few of the brightest star clusters. C. Star Catalogues This chapter provides technical descriptions on how Stellarium records its star catalogues, and the related file formats. C.1 Stellarium’s Sky Model C.1.1 Zones The celestial sphere is split into zones, which correspond to the triangular faces of a geodesic sphere. The number of zones (faces) depends on the level of sub-division of this sphere. The lowest level, 0, is an icosahedron (20 faces), subsequent levels L of sub-division give the number of zones n as: n = 20 · 4L (C.1) Stellarium uses levels 0 to 7 in the existing star catalogues. Star Data Records contain the position of a star as an offset from the central position of the zone in which that star is located, thus it is necessary to determine the vector from the observer to the centre of a zone, and add the star’s offsets to find the absolute position of the star on the celestial sphere. This position for a star is expressed as a 3-dimensional vector which points from the observer (at the centre of the geodesic sphere) to the position of the star as observed on the celestial sphere. C.2 Star Catalogue File Format C.2.1 General Description Stellarium’s star catalogue data is kept in the stars/default sub-directory of the Installation Directory and/or User Directory (see section 5.1). The main catalogue data is split into several files: Appendix C. Star Catalogues 252 There also exist some control and reference files: gcvs_hip_part.dat wds_hip_part.dat cross-id.dat stars.ini name.fab When Stellarium starts, it reads the stars.ini file, from which it determines the names of the other files, which it then loads. The files and contain reference data for the main catalogue files. The file gcvs_hip_part.dat contains data about variables stars (see section C.3) and file wds_hip_part.dat contains data about double stars (see section C.4) which again contains references into the main catalogue files. The file cross-id.dat (see section C.5) contains cross-identification data between HIP, SAO, HD and HR designations. A given catalogue file models stars for one and only one level (i.e. for a fixed number of zones), which is recorded in the header of the file. Individual star records do not contain full positional coordinates, instead they contain coordinates relative to the central position of the zone they occupy. Thus, when parsing star catalogues, it is necessary to know about the zone model to be able to extract positional data. File Data Type 0 0 0 1 1 2 2 2 2 Data Record Size 28 bytes 28 bytes 28 bytes 10 bytes 10 bytes 8 bytes 8 bytes 8 bytes 8 bytes Geodesic Level 0 1 2 3 4 5 6 7 7 #Records 4,979 21,806 150,850 425,807 1,692,779 7,083,058 24,670,782 50,733,321 92,304,337 Notes Hipparcos Hipparcos Hipparcos Tycho 2 Tycho 2 NOMAD NOMAD NOMAD NOMAD For a given catalogue file, there may be one of three formats for the actual star data. The variation comes from the source of the data – the larger catalogues of fainter stars providing less data per star than the brighter star catalogues. See tables Stellarium’s star catalogue and for details. Stellarium’s star catalogues are based on Hipparcos (Anderson and Francis, 2012; ESA, 1997), Tycho 2 (Høg et al., 2000) and NOMAD (Zacharias et al., 2004) catalogues. C.2.2 File Sections The catalogue files are split into three main sections as described in table File sections. C.2 Star Catalogue File Format C.2.3 253 Section Offset Description File Header Record 0 Zone Records 32 Star Data Records 32+4n Contains magic number, geodesic subdivision level, and magnitude range A list of how many records there are for each zone. The length of the zones section depends on the level value from the header This section of the file contains fixed-size star records, as described below. Records do not contain zone information, which must be inferred by counting how many records have been read so far and switching zones when enough have been read to fill the number of stars for the zone, as specified in the zones section above. The value of n used in the offset description is the number of zones, as described above. Record Types File Header Record The File Header Record describes file-wide settings. It also contains a magic number which servers as a file type identifier. See table C.1. Name Offset Type Size Description Magic 0 int 4 Data Type 4 int 4 Major Version Minor Version Level 8 12 16 int int int 4 4 4 Magnitude Minimum 20 int 4 Magnitude Range Magnitude Steps 24 28 int int 4 4 magic number which identifies the file as a star catalogue. 0xde0955a3 type of the file, which defines the size and structure of the Star Data record for the file. file format major version number file format minor version number sets the level of sub-division of the geodesic sphere used to create the zones. 0 means an icosahedron (20 triangular faces), subsequent levels of sub-division lead to numbers of zones as described in section C.2.3 low bound of the magnitude scale for values in this file. Note that this is still an integer in Stellarium’s own internal representation range of magnitudes expressed in this file number of steps used to describes values in the range Table C.1: Header Record Zone Records The Zone Records section of the file lists the number of star records there are per zone. The number of zones is determined from the level value in the File Header Record, as described in section Appendix C. Star Catalogues 254 Zones. The Zones section is simply a list of integer values which describe the number of stars for each zone. The total length of the Zones section depends on the number of zones. See table C.2. Name Offset Type Size Description num stars in zone 0 0 int 4 num stars in zone 1 4 int 4 number of records in this file which are in zone 0 number of records is this file which are in zone 1 ... num stars in zone n 4n int 4 number of records is this file which are in zone n Table C.2: Zones section Star Data Records After the Zones section, the actual star data starts. The star data records themselves do not contain the zone in which the star belongs. Instead, the zone is inferred from the position of the record in the file. For example, if the Zone Records section of the file says that the first 100 records are for zone 0, the next 80 for zone 1 and so on, it is possible to infer the zone for a given record by counting how many records have been read so far. The actual record structure depends on the value of the Data Type, as found in the File Header Record. See tables C.3, C.4 and C.5 for record structure details. It should be noted that although the positional data loses accuracy as one progresses though the Star Record Types, this is compensated for by the face that the number of zones is much higher for the files where the smaller precision position fields are used, so the actual resolution on the sky isn’t significantly worse for the type 1 and 2 records in practice. Name Offset Type Size Description hip component_ids 0 3 int unsigned char 3 1 x0 4 int 4 x1 8 int 4 b_v 9 unsigned char 1 mag 10 unsigned char 1 Hipparcos catalogue number index to an array of catalogue number suffixes. The list is read from the file. The value of this field turns out to be the line number in the file - 1 position of the star relative to the central point in the star’s zone, in axis 1 position of the star relative to the central point in the star’s zone, in axis 2 magnitude level in B-V colour. This value refers to one of 256 discrete steps in the magnitude range for the file magnitude level in the V-I colour. This value refers to one of 256 discrete steps in the magnitude range for the file C.3 Variable Stars 255 sp_int 11 unsigned short int 2 dx0 dx1 plx 13 17 21 int int int 4 4 4 index into an array of spectral type descriptions which is taken from the file, the index corresponds to the line number in the file - 1 proper motion of the star in axis 1 proper motion of the star in axis 2 parallax of the star. To get the actual value, divide by 10000. Table C.3: Star Data Record Type 0 Name Offset Type x0 0 int x1 dx0 dx1 b_v mag Size Description 20 bits position of the star relative to the central point in the star’s zone, in axis 1 20 bits int 20 bits position of the star relative to the central point in the star’s zone, in axis 2 40 bits int 14 bits proper motion of the star in axis 1 54 bits int 14 bits proper motion of the star in axis 2 68 bits unsigned int 7 bits magnitude level in B-V colour. This value refers to one of 128 discrete steps in the magnitude range for the file 75 bits unsigned int 5 bits magnitude level in the V-I colour. This value refers to one of 32 discrete steps in the magnitude range for the file Table C.4: Star Data Record Type 1 C.3 Variable Stars Since version 0.12.2 Stellarium supports the subset of variable stars from GCVS1 which have HIP identificators (i.e., stars from the Hipparcos catalog). Stellarium’s Catalog of Variable Stars is based on the “General Catalogue of Variable Stars (Samus+ 2007-2015)” (Samus et al., 2015). C.3.1 Variable Star Catalog File Format General Description Stellarium’s Variable Stars catalog data is kept in the stars/default sub-directory of the Installation Directory and/or User Directory (see section 5.1). File Format The gcvs_hip_part.dat file contains data about 6916 Variable Stars (see section 18.2.5) which have HIP identificators and are stored in a plain text format with tab delimiter (Table C.6). 1 Appendix C. Star Catalogues 256 Name Offset Type x0 0 int x1 b_v mag Size Description 18 bits position of the star relative to the central point in the star’s zone, in axis 1 18 bits int 18 bits position of the star relative to the central point in the star’s zone, in axis 2 36 bits unsigned int 7 bits magnitude level in B-V colour. This value refers to one of 128 discrete steps in the magnitude range for the file 43 bits unsigned int 5 bits magnitude level in the V-I colour. This value refers to one of 32 discrete steps in the magnitude range for the file Table C.5: Star Data Record Type 2 Name Type Description HIP int GCVS Type Max MFlag string string float int Min I Min II V Epoch Period M-m Spectrum float float char float float float string This is the HIP identificator for the star. Used for reference to the main star catalogue. This is the GCVS designation for the variable star. Type of variability. Magnitude at maximum brightness. Magnitude flag code (0=No flag; 1="(" if max. magnitude is an amplitude; 2="<" if max. magnitude is a bright limit; 3=">" is max. magnitude is a faint limit). First minimum magnitude or amplitude. Second minimum magnitude. The photometric system for magnitudes. Epoch for maximum or minimum light (in Julian days). Period for the variable star (in days). Rising time or duration of the eclipse (in percent). Spectral class of the variable star. Table C.6: Variable Star Catalog File Format C.3.2 GCVS Variability Types An improved system of variability classification is used in the fourth edition of the GCVS, based on recent developments in classification principles and taking into account the suggestions of a number of specialists. Variability types are grouped according to the major astrophysical reasons for variability. All of these classes include objects of a dissimilar nature that belong to different types of light variability. On the other hand, an object may be variable because of almost all of the possible reasons or because of any combination of them. If a variable belongs to several types of variability, the types are joined in the data field by a “+” sign, e.g., E+UG, UV+BY. Despite considerable success in understanding stellar variability processes, the classification adopted in the Catalogue is far from perfect. This is especially the case for explosive, symbiotic and novalike variables; X-ray sources; and peculiar objects. C.3 Variable Stars 257 You can read about latest different types of variability at VIZIER2 . Eruptive Variable Stars Eruptive variables are stars varying in brightness because of violent processes and flares occurring in their chromospheres and coronae. The light changes are usually accompanied by shell events or mass outflow in the form of stellar winds of variable intensity and/or by interaction with the surrounding interstellar medium. This class includes the following types: BE It becomes more and more clear that, although the majority of Be stars are photometrically variable, not all of them could be properly called GCAS variables. Quite a number of them show small-scale variations not necessarily related to shell events; in some cases the variations are quasi-periodic. By now we are not able to present an elaborated system of classification for Be variables, but we adopt a decision that in the cases when a Be variable cannot be readily described as a GCAS star we give simply BE for the type of variability. FU Orion variables of the FU Orionis type. Characterized by gradual increases in brightness by about 6 mag in several months, followed by either almost complete constancy at maximum that is sustained for long periods of time or slow decline by 1-2 mag. Spectral types at maximum are in the range Ae(alpha) - Gpe(alpha). After an outburst, a gradual development of an emission spectrum is observed and the spectral type becomes later. These variables probably mark one of the evolutionary stages of T Tauri-type Orion variables (INT), as evidenced by an outburst of one member, V1057 Cyg, but its decline (2.5 mag in 11 years) commenced immediately after maximum brightness was attained. All presently known FU Ori variables are coupled with reflecting cometary nebulae. GCAS Eruptive irregular variables of the Gamma Cas type. These are rapidly rotating B III-IVe stars with mass outflow from their equatorial zones. The formation of equatorial rings or disks is often accompanied by temporary fading. Light amplitudes may reach 1.5 mag in V. I Poorly studied irregular variables with unknown features of light variations and spectral types. This is a very inhomogeneous group of objects. IA Poorly studied irregular variables of early (O-A) spectral type. IB Poorly studied irregular variables of intermediate (F-G) to late (K-M) spectral type. IN Orion variables. Irregular, eruptive variables connected with bright or dark diffuse nebulae or observed in the regions of these nebulae. Some of them may show cyclic light variations caused by axial rotation. In the Spectrum-Luminosity diagram, they are found in the area of the main sequence and subgiants. They are probably young objects that, during the course of further evolution, will become light-constant stars on the zero-age main sequence (ZAMS). The range of brightness variations may reach several magnitudes. In the case of rapid light variations having been observed (up to 1 mag in 1-10 days), the letter “S” is added to the symbol for the type (INS). This type may be divided into the following subtypes: INA Orion variables of early spectral types (B-A or Ae). They are often characterized by occasional abrupt Algol-like fadings (T Ori); INB Orion variables of intermediate and late spectral types, F-M or Fe-Me (BH Cep, AH Ori). F-type stars may show Algol-like fadings similar to those of many INA stars; K-M stars may produce flares along with irregular light variations; INT,IT Orion variables of the T Tauri type. Stars are assigned to this type on the basis of the following (purely spectroscopic) criteria: spectral types are in the range Fe-Me. The spectra of most typical stars resemble the spectrum of the solar chromosphere. The feature specific to the type is the presence of the flourescent emission lines Fe II 4046, 4132 A (anomalously intense in the spectra of these 2 258 Appendix C. Star Catalogues stars), emission lines [Si II] and [O I], as well as the absorption line Li I 6707 A. These variables are usually observed only in diffuse nebulae. If it is not apparent that the star is associated with a nebula, the letter “N” in the symbol for the type may be omitted, e.g., IT (RW AUR); IN(YY) Some Orion variables (YY Ori) show the presence of absorption components on the redward sides of emission lines, indicating the infall of matter toward the stars’ surfaces. In such cases, the symbol for the type may be accompanied by the symbol “YY”. IS Rapid irregular variables having no apparent connection with diffuse nebulae and showing light changes of about 0.5 - 1.0 mag within several hours or days. There is no strict boundary between rapid irregular and Orion variables. If a rapid irregular star is observed in the region of a diffuse nebula, it is considered an Orion variable and designated by the symbol INS. To attribute a variable to the IS type, it is necessary to take much care to be certain that its light changes are really not periodic. Quite a number of the stars assigned to this type in the third edition of the GCVS turned out to be eclipsing binary systems, RR Lyrae variables, and even extragalactic BL Lac objects. ISA Rapid irregular variables of the early spectral types, B-A or Ae; ISB Rapid irregular variables of the intermediate and late spectral types, F-M and Fe-Me. RCB Variables of the R Coronae Borealis type. These are hydrogen-poor, carbon- and heliumrich, high-luminosity stars belonging to the spectral types Bpe-R, which are simultaneously eruptive and pulsating variables. They show slow nonperiodic fadings by 1-9 mag in V lasting from a month or more to several hundred days. These changes are superposed on cyclic pulsations with amplitudes up to several tenths of a magnitude and periods in the range 30-100 days. RS Eruptive variables of the RS Canum Venaticorum type. This type is ascribed to close binary systems with spectra showing Ca II H and K in emission, their components having enhanced chromospheric activity that causes quasi-periodic light variability. The period of variation is close to the orbital one, and the variability amplitude is usually as great as 0.2 mag in V (UX Ari). They are X-ray sources and rotating variables. RS CVn itself is also an eclipsing system (see below). SDOR Variables of the S Doradus type. These are eruptive, high-luminosity Bpec-Fpec stars showing irregular (sometimes cyclic) light changes with amplitudes in the range 1-7 mag in V. They belong to the brightest blue stars of their parent galaxies. As a rule, these stars are connected with diffuse nebulae and surrounded by expanding envelopes (P Cyg, Eta Car). UV Eruptive variables of the UV Ceti type, these are K Ve-M Ve stars sometimes displaying flare activity with amplitudes from several tenths of a magnitude up to 6 mag in V. The amplitude is considerably greater in the ultraviolet spectral region. Maximum light is attained in several seconds or dozens of seconds after the beginning of a flare; the star returns to its normal brightness in several minutes or dozens of minutes. UVN Flaring Orion variables of spectral types Ke-Me. These are phenomenologically almost identical to UV Cet variables observed in the solar neighborhood. In addition to being related to nebulae, they are normally characterized by being of earlier spectral type and greater luminosity, with slower development of flares (V389 Ori). They are possibly a specific subgroup of INB variables with irregular variations superimposed by flares. WR Eruptive Wolf-Rayet variables. Stars with broad emission features of He I and He II as well as C II-C IV, O II-O IV, and N III-N V. They display irregular light changes with amplitudes up to 0.1 mag in V, which are probably caused by physical processes, in particular, by nonstable C.3 Variable Stars 259 mass outflow from their atmospheres. Pulsating Variable Stars Pulsating variables are stars showing periodic expansion and contraction of their surface layers. The pulsations may be radial or nonradial. A radially pulsating star remains spherical in shape, while in the case of nonradial pulsations the star’s shape periodically deviates from a sphere, and even neighboring zones of its surface may have opposite pulsation phases. Depending on the period value, on the mass and evolutionary status of the star, and on the scale of pulsational phenomena, the following types of pulsating variables may be distinguished: ACYG Variables of the Alpha Cygni type, which are nonradially pulsating supergiants of BepAepIa spectral types. The light changes with amplitudes of the order of 0.1 mag often seem irregular, being caused by the superposition of many oscillations with close periods. Cycles from several days to several weeks are observed. BCEP Variables of the Beta Cephei type (Beta Cep, Beta CMa), which are pulsating O8-B6 I-V stars with periods of light and radial-velocity variations in the range of 0.1 - 0.6 days and light amplitudes from 0.01 to 0.3 mag in V. The light curves are similar in shape to average radial-velocity curves but lag in phase by a quarter of the period, so that maximum brightness corresponds to maximum contraction, i.e., to minimum stellar radius. The majority of these stars probably show radial pulsations, but some (V469 Per) display nonradial pulsations; multiperiodicity is characteristic of many of these stars. BCEPS A short-period group of Beta Cep variables. The spectral types are B2-B3 IV-V; periods and light amplitudes are in the ranges 0.02 - 0.04 days and 0.015 - 0.025 days, respectively, i.e., an order of magnitude smaller than the normally observed ones. BLBOO The so-called “anomalous Cepheids”, i.e. stars with periods characteristic of comparatively long-period RRAB variables, but considerably brighter by luminosity (BL Boo = NGC 5466 V19). CEP Cepheids. Radially pulsating, high luminosity (classes Ib-II) variables with periods in the range of 1-135 days and amplitudes from several hundredths to 2 mag in V (in the B band, the amplitudes are greater). Spectral type at maximum light is F; at minimum, the types are G-K. The longer the period of light variation, the later is the spectral type. The maximum of the surface-layer expansion velocity almost coinciding with maximum light. CEP(B) Cepheids (TU Cas, V 367 Sct) displaying the presence of two or more simultaneously operating pulsation modes (usually the fundamental tone with the period P0 and the first overtone P1). The periods P0 are in the range from 2 to 7 days, with the ratio P1/P0 approx. 0.71. CW Variables of the W Virginis type. These are pulsating variables of the galactic spherical component (old disk) population with periods of approximately 0.8 to 35 days and amplitudes from 0.3 to 1.2 mag in V. They obey a period-luminosity relation different from that for Delta Cep variables (see DCEP). For an equal period value, the W Vir variables are fainter than the Delta Cep stars by 0.7 - 2 mag. The light curves of W Vir variables for some period intervals differ from those of Delta Cep variables for corresponding periods either by amplitudes or by the presence of humps on their descending branches, sometimes turning into broad flat maxima. W Vir variables are present in globular clusters and at high galactic latitudes. They may be separated into the following subtypes: CWA W Vir variables with periods longer than 8 days (W Vir); CWB W Vir variables with periods shorter than 8 days (BL Her). DCEP These are the classical cepheids, or Delta Cep-type variables. Comparatively young objects that have left the main sequence and evolved into the instability strip of the HertzsprungRussell (H-R) diagram, they obey the well-known Cepheid period-luminosity relation and 260 Appendix C. Star Catalogues belong to the young disk population. DCEP stars are present in open clusters. They display a certain relation between the shapes of their light curves and their periods. DCEPS These are Delta Cep variables having light amplitudes <0.5 mag in V (<0.7 mag in B) and almost symmetrical light curves (M-m approx. 0.4 - 0.5 periods); as a rule, their periods do not exceed 7 days. They are probably first-overtone pulsators and/or are in the first transition across the instability strip after leaving the main sequence (SU Cas). Traditionally, both Delta Cep and W Vir stars are quite often called Cepheids because it is often impossible to discriminate between them on the basis of the light curves for periods in the range 3 - 10 days. However, these are distinct groups of entirely different objects in different evolutionary stages. One of the significant spectral differences between W Vir stars and Cepheids is the presence, during a certain phase interval, of hydrogen-line emission in the former and of Ca II H and K emission in the latter. DSCT Variables of the Delta Scuti type. These are pulsating variables of spectral types A0-F5 III-V displaying light amplitudes from 0.003 to 0.9 mag in V (usually several hundredths of a magnitude) and periods from 0.01 to 0.2 days. The shapes of the light curves, periods, and amplitudes usually vary greatly. Radial as well as nonradial pulsations are observed. The variability of some members of this type appears sporadically and sometimes completely ceases, this being a consequence of strong amplitude modulation with the lower value of the amplitude not exceeding 0.001 mag in some cases. The maximum of the surface layer expansion does not lag behind the maximum light for more than 0.1 periods. DSCT stars are representatives of the galactic disk (flat component) and are phenomenologically close to the SX Phe variables. DSCTC Low amplitude group of Delta Sct variables (light amplitude <0.1 mag in V). The majority of this type’s representatives are stars of luminosity class V; objects of this subtype generally are representative of the Delta Sct variables in open clusters. GDOR Gamma Doradus stars. Early type F dwarfs showing (multiple) periods from several tenths of a day to slightly in excess of one day. Amplitudes usually do not exceed 0.1 mag. Presumably low degree g-mode non-radial pulsators. Prototype: gamma Dor. L Slow irregular variables. The light variations of these stars show no evidence of periodicity, or any periodicity present is very poorly defined and appears only occasionally. Like for the type I, stars are often attributed to this type because of being insufficiently studied. Many type L variables are really semiregulars or belong to other types. LB Slow irregular variables of late spectral types (K, M, C, S); as a rule, they are giants (CO Cyg). This type is also ascribed, in the GCVS, to slow red irregular variables in the case of unknown spectral types and luminosities. LC Irregular variable supergiants of late spectral types having amplitudes of about 1 mag in V (TZ Cas). LPB The comparatively long-period pulsating B stars (periods exceeding (LBV) one day). M Mira (Omicron) Ceti-type variables. These are long-period variable giants with characteristic late-type emission spectra (Me, Ce, Se) and light amplitudes from 2.5 to 11 mag in V. Their periodicity is well pronounced, and the periods lie in the range between 80 and 1000 days. Infrared amplitudes are usually less than in the visible and may be <2.5 mag. For example, in the K band they usually do not exceed 0.9 mag. If the amplitudes exceed 1 - 1.5 mag , but it is not certain that the true light amplitude exceeds 2.5 mag, the symbol “M” is followed by a colon, or the star is attributed to the semiregular class with a colon following the symbol for that type (SR). PVTEL Variables of the PV Telescopii type. These are helium supergiant Bp stars with weak hydrogen lines and enhanced lines of He and C. They pulsate with periods of approximately C.3 Variable Stars 261 0.1 to 1 days, or vary in brightness with an amplitude of 0.1 mag in V during a time interval of about a year. RPHS Very rapidly pulsating hot (subdwarf B) stars. Typical periods are hundreds of seconds, amplitudes are within several hundredths of a magnitude. Prototype: V361 Hya = EC 14026-2647. RR Variables of the RR Lyrae type, which are radially-pulsating giant A-F stars having amplitudes from 0.2 to 2 mag in V. Cases of variable light-curve shapes as well as variable periods are known. If these changes are periodic, they are called the Blazhko effect. Traditionally, RR Lyrae stars are sometimes called short-period Cepheids or cluster-type variables. The majority of these stars belong to the spherical component of the Galaxy; they are present, sometimes in large numbers, in some globular clusters, where they are known as pulsating horizontal-branch stars. Like Cepheids, maximum expansion velocities of surface layers for these stars practically coincide with maximum light. RR(B) RR Lyrae variables showing two simultaneously operating pulsation modes, the fundamental tone with the period P0 and the first overtone, P1 (AQ Leo). The ratio P1/P0 is approximately 0.745; RRAB RR Lyrae variables with asymmetric light curves (steep ascending branches), periods from 0.3 to 1.2 days, and amplitudes from 0.5 to 2 mag in V; RRC RR Lyrae variables with nearly symmetric, sometimes sinusoidal, light curves, periods from 0.2 to 0.5 days, and amplitudes not greater than 0.8 mag in V (SX UMa). RV Variables of the RV Tauri type. These are radially pulsating supergiants having spectral types F-G at maximum light and K-M at minimum. The light curves are characterized by the presence of double waves with alternating primary and secondary minima that can vary in depth so that primary minima may become secondary and vice versa. The complete light amplitude may reach 3-4 mag in V. Periods between two adjacent primary minima (usually called formal periods) lie in the range 30-150 days (these are the periods appearing in the Catalogue). Two subtypes, RVA and RVB, are recognized: RVA RV Tauri variables that do not vary in mean magnitude (AC Her); RVB RV Tauri variables that periodically (with periods from 600 to 1500 days and amplitudes up to 2 mag in V) vary in mean magnitude (DF Cyg, RV Tau). SR Semiregular variables, which are giants or supergiants of intermediate and late spectral types showing noticeable periodicity in their light changes, accompanied or sometimes interrupted by various irregularities. Periods lie in the range from 20 to >2000 days, while the shapes of the light curves are rather different and variable, and the amplitudes may be from several hundredths to several magnitudes (usually 1-2 mag in V). SRA Semiregular late-type (M, C, S or Me, Ce, Se) giants displaying persistent periodicity and usually small (<2.5 mag in V) light amplitudes (Z Aqr). Amplitudes and lightcurve shapes generally vary and periods are in the range of 35-1200 days. Many of these stars differ from Miras only by showing smaller light amplitudes; SRB Semiregular late-type (M, C, S or Me, Ce, Se) giants with poorly defined periodicity (mean cycles in the range of 20 to 2300 days) or with alternating intervals of periodic and slow irregular changes, and even with light constancy intervals (RR CrB, AF Cyg). Every star of this type may usually be assigned a certain mean period (cycle), which is the value given in the Catalogue. In a number of cases, the simultaneous presence of two or more periods of light variation is observed; SRC Semiregular late-type (M, C, S or Me, Ce, Se) supergiants (Mu Cep) with amplitudes of about 1 mag and periods of light variation from 30 days to several thousand days; SRD Semiregular variable giants and supergiants of F, G, or K spectral types, sometimes with emission lines in their spectra. Amplitudes of light variation are in the range from 262 Appendix C. Star Catalogues 0.1 to 4 mag, and the range of periods is from 30 to 1100 days (SX Her, SV UMa). SRS Semiregular pulsating red giants with short period (several days to a month), probably high-overtone pulsators. Prototype: AU Ari. SXPHE Phenomenologically, these resemble DSCT (Delta Sct) variables and are pulsating subdwarfs of the spherical component, or old disk galactic population, with spectral types in the range A2-F5. They may show several simultaneous periods of oscillation, generally in the range 0.04-0.08 days, with variable-amplitude light changes that may reach 0.7 mag in V. These stars are present in globular clusters. ZZ ZZ Ceti variables. These are nonradially pulsating white dwarfs that change their brightnesses with periods from 30 s to 25 min and amplitudes from 0.001 to 0.2 mag in V. They usually show several close period values. Flares of 1 mag are sometimes observed; however, these may be explained by the presence of close UV Ceti companions. These variables are divided into the following subtypes: ZZA ZZ Cet-type variables of DA spectral type (ZZ Cet) having only hydrogen absorption lines in their spectra; ZZB ZZ Cet-type variables of DB spectral type having only helium absorption lines in their spectra. ZZO ZZ Cet-type variables of the DO spectral type showing HeII and and CIV absorpion lines in their spectra. Rotating Variable Stars Variable stars with nonuniform surface brightness and/or ellipsoidal shapes, whose variability is caused by axial rotation with respect to the observer. The nonuniformity of surface brightness distributions may be caused by the presence of spots or by some thermal or chemical inhomogeneity of the atmosphere caused by a magnetic field whose axis is not coincident with the rotation axis. These stars are subdivided into the following types: ACV Alpha2 Canum Venaticorum variables. These are main-sequence stars with spectral types B8p-A7p and displaying strong magnetic fields. Spectra show abnormally strong lines of Si, Sr, Cr, and rare earths whose intensities vary with rotation. They exhibit magnetic field and brightness changes (periods of 0.5-160 days or more). The amplitudes of the brightness changes are usually within 0.01-0.1 mag in V. ACVO Rapidly oscillating Alpha2 CVn variables. These are nonradially pulsating, rotating magnetic variables of Ap spectral type (DO Eri). Pulsation periods are in the range of 6-12 mmag (0.004-0.01 days), while amplitudes of light variation caused by the pulsation are about 0.01 mag in V. The pulsational variations are superposed on those caused by rotation. BY BY Draconis-type variables, which are emission-line dwarfs of dKe-dMe spectral type showing quasiperiodic light changes with periods from a fraction of a day to 120 days and amplitudes from several hundredths to 0.5 mag in V. The light variability is caused by axial rotation of a star with a variable degree of nonuniformity of the surface brightness (spots) and chromospheric activity. Some of these stars also show flares similar to those of UV Cet stars, and in those cases they also belong to the latter type and are simultaneously considered eruptive variables. ELL Rotating ellipsoidal variables (b Per, Alpha Vir). These are close binary systems with ellipsoidal components, which change combined brightnesses with periods equal to those of orbital motion because of changes in emitting areas toward an observer, but showing no eclipses. Light amplitudes do not exceed 0.1 mag in V. FKCOM FK Comae Berenices-type variables. These are rapidly rotating giants with nonuniform surface brightnesses, which have G-K spectral types with broad H and K Ca II emission C.3 Variable Stars 263 and sometimes Halpha. They may also be spectroscopic binary systems. Periods of light variation (up to several days) are equal to rotational periods, and amplitudes are several tenths of a magnitude. It is not excluded that these objects are the product of further evolution of EW (W UMa) close binary systems (see below). PSR Optically variable pulsars (CM Tau), which are rapidly rotating neutron stars with strong magnetic fields, radiating in the radio, optical, and X-ray regions. Pulsars emit narrow beams of radiation, and periods of their light changes coincide with rotational periods (from 0.004 to 4 s), while amplitudes of the light pulses reach 0.8 mag. R Close binary systems characterized by the presence of strong reflection (re-radiation) of the light of the hot star illuminating the surface of the cooler companion. Light curves are sinusoidal with the period equal to Porb, maximum brightness coinciding with the passage of the hot star in front of the companion. The eclipse may be absent. The range of light variation is about 0.5-1.0mag V (KV Vel). SXARI SX Arietis-type variables. These are main-sequence B0p-B9p stars with variable-intensity He I and Si III lines and magnetic fields. They are sometimes called helium variables. Periods of light and magnetic field changes (about 1 day) coincide with rotational periods, while amplitudes are approximately 0.1 mag in V. These stars are high-temperature analogs of the ACV variables. Cataclysmic (Explosive and Novalike) Variables These are variable stars showing outbursts caused by thermonuclear burst processes in their surface layers (novae) or deep in their interiors (supernovae). We use the term “novalike” for variables that show novalike outbursts caused by rapid energy release in the surrounding space (UG-type stars - see below) and also for objects not displaying outbursts but resembling explosive variables at minimum light by their spectral (or other) characteristics. The majority of explosive and novalike variables are close binary systems, their components having strong mutual influence on the evolution of each star. It is often observed that the hot dwarf component of the system is surrounded by an accretion disk formed by matter lost by the other, cooler, and more extended component. This category is subdivided into the following types: N Novae. Close binary systems with orbital periods from 0.05 to 230 days. One of the components of these systems is a hot dwarf star that suddenly, during a time interval from one to several dozen or several hundred days, increases its brightness by 7-19 mag in V, then returns gradually to its former brightness over several months, years, or decades. Small changes at minimum light may be present. Cool components may be giants, subgiants, or dwarfs of K-M type. The spectra of novae near maximum light resemble A-F absorption spectra of luminous stars at first. Then broad emission lines (bands) of hydrogen, helium, and other elements with absorption components indicating the presence of a rapidly expanding envelope appear in the spectrum. As the light decreases, the composite spectrum begins to show forbidden lines characteristic of the spectra of gas nebulae excited by hot stars. At minimum light, the spectra of novae are generally continuous or resemble the spectra of Wolf-Rayet stars. Only spectra of the most massive systems show traces of cool components. Some novae reveal pulsations of hot components with periods of approximately 100 s and amplitudes of about 0.05 mag in V after an outburst. Some novae eventually turn out to be eclipsing systems. According to the features of their light variations, novae are subdivided into fast (NA), slow (NB), very slow (NC), and recurrent (NR) categories. NA Fast novae displaying rapid light increases and then, having achieved maximum light, fading by 3 mag in 100 or fewer days (GK Per); NB Slow novae that fade after maximum light by 3 mag in >= 150 days (RR Pic). Here the presence of the well-known “dip” in the light curves of novae similar to T Aur and DQ 264 Appendix C. Star Catalogues Her is not taken into account: The rate of fading is estimated on the basis of a smooth curve, its parts before and after the “dip” being a direct continuation of one another; NC Novae with a very slow development and remaining at maximum light for more than a decade, then fading very slowly. Before an outburst these objects may show longperiod light changes with amplitudes of 1-2 mag in V (RR Tel); cool components of these systems are probably giants or supergiants, sometimes semiregular variables, and even Mira variables. Outburst amplitudes may reach 10 mag. High excitation emission spectra resemble those of planetary nebulae, Wolf-Rayet stars, and symbiotic variables. The possibility that these objects are planetary nebulae in the process of formation is not excluded; NL Novalike variables, which are insufficiently studied objects resembling novae by the characteristics of their light changes or by spectral features. This type includes, in addition to variables showing novalike outbursts, objects with no bursts ever observed; the spectra of novalike variables resemble those of old novae, and small light changes resemble those typical for old novae at minimum light. However, quite often a detailed investigation makes it possible to reclassify some representatives of this highly inhomogeneous group of objects into other types; NR Recurrent novae, which differ from typical novae by the fact that two or more outbursts (instead of a single one) separated by 10-80 years have been observed (T CrB). SN Supernovae (B Cas, CM Tau). Stars that increase, as a result of an outburst, their brightnesses by 20 mag and more, then fade slowly. The spectrum during an outburst is characterized by the presence of very broad emission bands, their widths being several times greater than those of the bright bands observed in the spectra of novae. The expansion velocities of SN envelopes are in the thousands of km/s. The structure of a star after outburst alters completely. An expanding emission nebula results and a (not always observable) pulsar remains at the position of the original star. According to the light curve shape and the spectral features, supernovae are subdivided into types I and II. SNI Type I supernovae. Absorption lines of Ca II, Si, etc., but no hydrogen lines are present in the spectra. The expanding envelope almost lacks hydrogen. During 20-30 days following maximum light, the brightness decreases by approximately 0.1 mag per day, then the rate of fading slows and reaches a constant value of 0.014/day; SNII Type II supernovae. Lines of hydrogen and other elements are apparent in their spectra. The expanding envelope consists mainly of H and He. Light curves show greater diversity than those of type I supernovae. Usually after 40-100 days since maximum light, the rate of fading is 0.1 mag per day. UG U Geminorum-type variables, quite often called dwarf novae. They are close binary systems consisting of a dwarf or subgiant K-M star that fills the volume of its inner Roche lobe and a white dwarf surrounded by an accretion disk. Orbital periods are in the range 0.05-0.5 days. Usually only small, in some cases rapid, light fluctuations are observed, but from time to time the brightness of a system increases rapidly by several magnitudes and, after an interval of from several days to a month or more, returns to the original state. Intervals between two consecutive outbursts for a given star may vary greatly, but every star is characterized by a certain mean value of these intervals, i.e., a mean cycle that corresponds to the mean light amplitude. The longer the cycle, the greater the amplitude. These systems are frequently sources of X-ray emission. The spectrum of a system at minimum is continuous, with broad H and He emission lines. At maximum these lines almost disappear or become shallow absorption lines. Some of these systems are eclipsing, possibly indicating that the primary minimum is caused by the eclipse of a hot spot that originates in the accretion disk from the infall of a gaseous stream from the K-M star. According to the characteristics of the light C.3 Variable Stars 265 changes, U Gem variables may be subdivided into three types: SS Cyg, SU UMa, and Z Cam. UGSS SS Cygni-type variables (SS Cyg, U Gem). They increase in brightness by 2-6 mag in V in 1-2 days and in several subsequent days return to their original brightnesses. The values of the cycle are in the range 10 days to several thousand; UGSU SU Ursae Majoris-type variables. These are characterized by the presence of two types of outbursts called “normal” and “supermaxima”. Normal, short outbursts are similar to those of UGSS stars, while supermaxima are brighter by 2 mag, are more than five times longer (wider), and occur several times less frequently. During supermaxima the light curves show superposed periodic oscillations (superhumps), their periods being close to the orbital ones and amplitudes being about 0.2-0.3 mag in V. Orbital periods are shorter than 0.1 days; companions are of dM spectral type; UGZ Z Camelopardalis-type stars. These also show cyclic outbursts, differing from UGSS variables by the fact that sometimes after an outburst they do not return to the original brightness, but during several cycles retain a magnitude between maximum and minimum. The values of cycles are from 10 to 40 days, while light amplitudes are from 2 to 5 mag in V. ZAND Symbiotic variables of the Z Andromedae type. They are close binaries consisting of a hot star, a star of late type, and an extended envelope excited by the hot star’s radiation. The combined brightness displays irregular variations with amplitudes up to 4 mag in V. A very inhomogeneous group of objects. Close Binary Eclipsing Systems We adopt a triple system of classifying eclipsing binary systems: according to the shape of the combined light curve, as well as to physical and evolutionary characteristics of their components. The classification based on light curves is simple, traditional, and suits the observers; the second and third classification methods take into account positions of the binary-system components in the (MV ,B-V) diagram and the degree of inner Roche lobe filling. Estimates are made by applying the simple criteria proposed by Svechnikov and Istomin (1979). The symbols for the types of eclipsing binary systems that we use are given below. Classification based on the shape of the light curve E Eclipsing binary systems. These are binary systems with orbital planes so close to the observer’s line of sight (the inclination i of the orbital plane to the plane orthogonal to the line of sight is close to 90 deg) that the components periodically eclipse each other. Consequently, the observer finds changes of the apparent combined brightness of the system with the period coincident with that of the components’ orbital motion. EA Algol (Beta Persei)-type eclipsing systems. Binaries with spherical or slightly ellipsoidal components. It is possible to specify, for their light curves, the moments of the beginning and end of the eclipses. Between eclipses the light remains almost constant or varies insignificantly because of reflection effects, slight ellipsoidality of components, or physical variations. Secondary minima may be absent. An extremely wide range of periods is observed, from 0.2 to >= 10000 days. Light amplitudes are also quite different and may reach several magnitudes. EB Beta Lyrae-type eclipsing systems. These are eclipsing systems having ellipsoidal components and light curves for which it is impossible to specify the exact times of onset and end of eclipses because of a continuous change of a system’s apparent combined brightness between eclipses; secondary minimum is observed in all cases, its depth usually being considerably smaller than that of the primary minimum; periods are mainly longer than 1 day. The components generally belong to early spectral types 266 Appendix C. Star Catalogues (B-A). Light amplitudes are usually <2 mag in V. EP Stars showing eclipses by their planets. Prototype: V0376 Peg. EW W Ursae Majoris-type eclipsing variables. These are eclipsers with periods shorter than 1 days, consisting of ellipsoidal components almost in contact and having light curves for which it is impossible to specify the exact times of onset and end of eclipses. The depths of the primary and secondary minima are almost equal or differ insignificantly. Light amplitudes are usually <0.8 mag in V. The components generally belong to spectral types F-G and later. Classification according to the components’ physical characteristics GS Systems with one or both giant and supergiant components; one of the components may be a main sequence star. PN Systems having, among their components, nuclei of planetary nebulae (UU Sge). RS RS Canum Venaticorum-type systems. A significant property of these systems is the presence in their spectra of strong Ca II H and K emission lines of variable intensity, indicating increased chromospheric activity of the solar type. These systems are also characterized by the presence of radio and X-ray emission. Some have light curves that exhibit quasi sine waves outside eclipses, with amplitudes and positions changing slowly with time. The presence of this wave (often called a distortion wave) is explained by differential rotation of the star, its surface being covered with groups of spots; the period of the rotation of a spot group is usually close to the period of orbital motion (period of eclipses) but still differs from it, which is the reason for the slow change (migration) of the phases of the distortion wave minimum and maximum in the mean light curve. The variability of the wave’s amplitude (which may be up to 0.2 mag in V) is explained by the existence of a long-period stellar activity cycle similar to the 11-year solar activity cycle, during which the number and total area of spots on the star’s surface vary. WD Systems with white-dwarf components. WR Systems having Wolf-Rayet stars among their components (V444 Cyg). Classification based on the degree of filling of inner Roche lobes AR Detached systems of the AR Lacertae type. Both components are subgiants not filling their inner equipotential surfaces. D Detached systems, with components not filling their inner Roche lobes. DM Detached main-sequence systems. Both components are main-sequence stars and do not fill their inner Roche lobes. DS Detached systems with a subgiant. The subgiant also does not fill its inner critical surface. DW Systems similar to W UMa systems in physical properties (KW, see below), but not in contact. K Contact systems, both components filling their inner critical surfaces. KE Contact systems of early (O-A) spectral type, both components being close in size to their inner critical surfaces. KW Contact systems of the W UMa type, with ellipsoidal components of F0-K spectral type. Primary components are main-sequence stars and secondaries lie below and to the left of the main sequence in the (MV,B-V) diagram. SD Semidetached systems in which the surface of the less massive component is close to its inner Roche lobe. The combination of the above three classification systems for eclipsers results in the assignment of multiple classifications for object types. These are separated by a solidus ("/") in the data field. Examples are: E/DM, EA/DS/RS, EB/WR, EW/KW, etc. C.3 Variable Stars 267 Optically Variable Close Binary Sources of Strong, Variable X-ray Radiation (X-ray Sources) AM AM Her type variables; close binary systems consisting of a dK-dM type dwarf and of a compact object with strong magnetic field, characterized by variable linear and circular polarization of light. The total range of light variations may reach 4-5 mag V. X Close binary systems that are sources of strong, variable X-ray emission and which do not belong to or are not yet attributed to any of the above types of variable stars. One of the components of the system is a hot compact object (white dwarf, neutron star, or possibly a black hole). X-ray emission originates from the infall of matter onto the compact object or onto an accretion disk surrounding the compact object. In turn, the X-ray emission is incident upon the atmosphere of the cooler companion of the compact object and is reradiated in the form of optical high-temperature radiation (reflection effect), thus making that area of the cooler companion’s surface an earlier spectral type. These effects lead to quite a peculiar complex character of optical variability in such systems. These objects may be subdivided into the following types: XB X-ray bursters. Close binary systems showing X-ray and optical bursts, their duration being from several seconds to ten minutes, with amplitudes of about 0.1 mag in V (V 801 Ara, V 926 Sco); XF Fluctuating X-ray systems showing rapid variations of X-ray (Cygnus X-1 = V1357 Cyg) and optical (V821 Ara) radiation on time scalesof dozens of milliseconds; XI X-ray irregulars. Close binary systems consisting of a hot compact object surrounded by an accretion disk and a dA - dM-type dwarf. These display irregular light changes on time scales of minutes and hours, and amplitudes of about 1 mag in V. Superposition of a periodic variation because of orbital motion is possible (V818 Sco); XJ X-ray binaries characterized by the presence of relativistic jets evident at X-ray and radio wavelengths, as well as in the optical spectrum in the form of emission components showing periodic displacements with relativistic velocities (V1343 Aql); XND X-ray, novalike (transient) systems containing, along with a hot compact object, a dwarf or subgiant of G-M spectral type. These systems occasionally rapidly increase in brightness by 4-9 mag in V, in the visible simultaneously with the X-ray range, with no envelope ejected. The duration of the outburst may be up to several months (V616 Mon); XNG X-ray, novalike (transient) systems with an early-type supergiant or giant primary component and a hot compact object as a companion. Following the main component’s outburst, the material ejected by it falls onto the compact object and causes, with a significant delay, the appearance of X rays. The amplitudes are about 1-2 mag in V (V725 Tau); XP X-ray pulsar systems. The primary component is usually an ellipsoidal early-type supergiant. The reflection effect is very small and light variability is mainly caused by the ellipsoidal primary component’s rotation. Periods of light changes are between 1 and 10 days; the period of the pulsar in the system is from 1 s to 100 min. Light amplitudes usually do not exceed several tenths of a magnitude (Vela X-1 = GP Vel); XPR X-ray pulsar systems featuring the presence of the reflection effect. They consist of a dB-dF-type primary and an X-ray pulsar, which may also be an optical pulsar. The mean light of the system is brightest when the primary component is irradiated by X rays; it is faintest during a low state of the X-ray source. The total light amplitude may reach 2-3 mag in V (HZ Her); XPRM,XM X-ray systems consisting of a late-type dwarf (dK-dM) and a pulsar with a strong magnetic field. Matter accretion on the compact object’s magnetic poles is Appendix C. Star Catalogues 268 accompanied by the appearance of variable linear and circular polarization; hence, these systems are sometimes known as “polars”. The amplitudes of the light changes are usually about 1 mag in V but, provided that the primary component is irradiated by X rays, the mean brightness of a system may increase by 3 mag in V. The total light amplitude may reach 4-5 mag in V (AM Her, AN UMa). If the beam of X-ray emission originating at the magnetic poles of the rotating hot compact object does not pass through the observer’s position and the system is not observed as a pulsar, the letter “P” in the above symbols for X-ray-system types is not used. If an X-ray system is also an eclipsing or an ellipsoidal variable, the X-ray symbol is preceded by “E” or “ELL” joined with the X-ray symbol by a "+" sign (e.g., E+X, ELL+X). Other Symbols In addition to the variable-star types described above, certain other symbols that need to be explained will be found in the Type data field: BLLAC Extragalactic BL Lacertae-type objects. These are compact quasistellar objects showing almost continuous spectra with weak emission and absorption lines and relatively rapid irregular light changes with amplitudes up to 3 mag in V or more. Sources of strong X-ray radiation and radio waves, their emission displays strong and variable linear polarization in the visible and infrared spectral regions. Some objects of this type, considered erroneously to be variable stars and designated in the GCVS system, will probably sometimes be included in the main table of the Catalogue in the future, too. CST Nonvariable stars, formerly suspected to be variable and hastily designated. Further observations have not confirmed their variability. GAL Optically variable quasistellar extragalactic objects (active galactic nuclei [AGNs]) considered to be variable stars by mistake. L: Unstudied variable stars with slow light changes. QSO Optically variable quasistellar extragalactic sources (quasars) that earlier were erroneously considered to be variable stars. S Unstudied variable stars with rapid light changes. * Unique variable stars outside the range of the classifications described above. These probably represent either short stages of transition from one variability type to another or the earliest and latest evolutionary stages of these types, or they are insufficiently studied members of future new types of variables. + If a variable star belongs to several types of light variability simultaneously, the types are joined in the Type field by a “+” sign (e.g., E+UG, UV+BY). : Uncertainty flag on Type of Variability C.4 Double Stars Since version 0.15.0 Stellarium supports the subset of double stars from WDS3 which have HIP identificators (i.e., stars from the Hipparcos catalog). Stellarium’s Catalog of Double Stars is based on the “The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog” (Mason et al., 2001). Cross reference data for WDS and HIP designations is based on the XHIP catalog (Anderson and Francis, 2012) through the astronomical database SIMBAD (Wenger et al., 2000). 3 C.5 Cross-Identification Data C.4.1 269 Double Star Catalog File Format General Description Stellarium’s Double Stars catalog data is kept in the stars/default sub-directory of the Installation Directory and/or User Directory (see section 5.1). File Format The wds_hip_part.dat file contains data about 16411 double stars which have HIP identificators and stored in plain text format with tab delimiters. Name Type HIP C.5 int WDS Observation Position Angle string int float Separation float Description HIP identificator for the star. Used for reference to the main star catalogue. WDS designation for the double star. Date of last satisfactory observation (in years). Position Angle at date of last satisfactory observation (in decimal degrees). Separation at date of last satisfactory observation (in arcsec). Cross-Identification Data Since version 0.14.0 Stellarium supports cross-identification between stars from Hipparcos (HIP) (Anderson and Francis, 2012), Smithsonian Astrophysical Observatory (SAO) Star Catalog J2000.0, Henry Draper Catalogue and Extension (HD) (Cannon and Pickering, 1993) and Catalogue of bright stars (Hoffleit, 1964) (BSC5 or HR) catalogues. C.5.1 Cross-Identification Catalog File Format General Description Stellarium’s Cross-Identification catalog data is kept in the stars/default sub-directory of the Installation Directory and/or User Directory (see section 5.1). File Format The file cross-id.dat contains cross reference data for catalogues HIP, SAO, HD and HR, which stored in the plain text format with tab delimiter. Name Type HIP int SAO HD HR int int int Description HIP identificator for the star. Used for reference to the main star catalogue. SAO identificator for the star. HD identificator for the star. HR identificator for the star. D. Configuration Files D.1 Program Configuration First, see 5.4 (The Main Configuration File) for information about the file config.ini, including its default installed location, and command line options that can affect how it is processed. The file config.ini (or a file which you can load instead with the --config option) is structured into the following parts. In addition, plugins can add a section named like the plugin (Exception: The Text User Interface plugin’s section is named [tui] for historical reasons). D.1.1   astro This section includes settings for the commonly displayed objects. ID Type Default Description apparent_magnitude_algorithm string ExpSup2013 nebula_magnitude_limit float 8.5 star_magnitude_limit float 6.5 planet_magnitude_limit float 6.5 planets_orbits_color_style string one_color Set algorithm for computation of apparent magnitude of the planets. Possible values: ExpSup2013, ExpSup1992, AstrAlm1984, Mueller1893 and Generic. Value of limiting magnitude for the deep-sky objects. Value of limiting magnitude for the stars. Sometimes you don’t want to display more stars when zooming in. Value of limiting magnitude for the planets. Sometimes you don’t want to display more planets when zooming in. Set the style of orbits color. Possible values: one_color, groups and max. Appendix D. Configuration Files 272 flag_nebula_magnitude_limit bool false Set to true to activate limit for showing deep-sky objects. Set to true to activate limit for showing stars Set to true to activate limit for showing planets. flag_star_magnitude_limit bool false flag_planet_magnitude_limit bool false extinction_mode_below_horizon string zero Set extinction mode for atmosphere below horizon. Possible values: zero, mirror and major_planets. flag_stars bool true flag_star_name bool true flag_star_additional_names bool true flag_planets bool true flag_planets_hints bool true flag_planets_orbits bool false flag_permanent_orbits bool false flag_planets_pointers bool false flag_planets_nomenclature bool false flag_hide_local_nomenclature bool true Set to false to hide the stars on startup Set to false to hide the star labels on start-up Set true to use additional names (also known as) for stars. Set to false to hide the planet labels on start-up Set to false to hide the planet hints on startup (names and circular highlights) Set to true to show the planet orbits on startup Set to true to show the orbit of planet, when planet is out of the viewport also. Set to true to show the planet pointer markers on startup Set to true to show the planetary nomenclature markers and labels Set to true to hide the planetary nomenclature items on the observer’s celestial body flag_light_travel_time bool true flag_object_trails bool false flag_isolated_trails bool true flag_isolated_orbits bool true flag_nebula bool true Should be true to improve accuracy in the movement of the planets by compensating for the time it takes for light to travel. This has a slight impact on performance, but is essential e.g. for Jupiter’s moons. Turns on and off drawing of object trails (which show the movement of the planets over time). Turns on and off drawing of isolated trails. Turns on and off drawing of isolated orbits. Set to false to hide the nebulae on start-up. D.1 Program Configuration 273 flag_nebula_name bool false Set to true to show the nebula labels on start-up. Set to true to suppress displaying of nebula textures. Sets the amount of hints [0. . . 10]. Sets the amount of labels [0. . . 10]. Set to false to hide the Milky Way. Sets the relative brightness with which the milky way is drawn. Typical [1. . . 3]. Set to false to hide the zodiacal light Sets the relative brightness with which the zodiacal light is drawn. Sets the magnitude of the nebulae whose name is shown. Enables/disables proportional markers for deep-sky objects. Enables/disables usage surface brightness for markers for deep-sky objects. flag_nebula_display_no_texture bool false nebula_hints_amount nebula_labels_amount flag_milky_way milky_way_intensity float float bool float 3.0 3.0 true 1.0 flag_zodiacal_light zodiacal_light_intensity bool float true 1.0 max_mag_nebula_name float 8.0 flag_nebula_hints_proportional bool false flag_surface_brightness_usage bool false flag_size_limits_usage bool false size_limit_min int 1 size_limit_max int 600 flag_use_type_filter bool false Enables/disables usage of the type filters for deep-sky objects. flag_nutation bool true Enables/disables usage nutation. flag_topocentric_coordinates bool true Enables/disables usage topocentric coordinates. flag_dso_designation_usage bool false flag_dso_outlines_usage bool false flag_dso_additional_names bool true If true, use designations of deep-sky objects on the sky instead of their common names. If true, use outlines for big deep-sky objects on the sky instead of their hints. Set true to use additional names (also known as) for deep-sky objects. flag_grs_custom bool false grs_longitude int 216 Enables/disables usage angular size filter for markers for deep-sky objects. Minimal angular size of visible deepsky objects in arcminutes. Maximum angular size of visible deep-sky objects in arcminutes. Turns on and off to using custom settings for calculation of position of Great Red Spot on Jupiter. Longitude of Great Red Spot on Jupiter in degrees. Appendix D. Configuration Files 274 D.1.2 grs_drift float 15.0 grs_jd float 2456901.5 grs_measurements_url string meteor_zhr int 10 de430_path flag_use_de430 string bool false de431_path flag_use_de431 string bool false flag_toast_survey bool false toast_survey_host string toast_survey_directory string results toast_survey_levels int 11  Annual drift of Great Red Spot on Jupiter in degrees. Initial JD for calculation of position of Great Red Spot on Jupiter. URL of recent measurements of GRS’ position1 . ZHR for sporadic meteors. Path to JPL DE430 ephemerides file. Enables/disables usage JPL DE430 ephemerides (if available). Path to JPL DE431 ephemerides file. Enables/disables usage JPL DE431 ephemerides (if available). Enables/disables usage Digitized Sky Survey in TOAST format. Host of Digitized Sky Survey storage data. Directory name of Digitized Sky Survey storage data. Count of levels for Digitized Sky Survey storage data.  astrocalc This section includes settings for the Astronomical Calculations feature. ID Type Default Description flag_ephemeris_markers bool true flag_ephemeris_dates bool false flag_ephemeris_magnitudes bool false flag_ephemeris_horizontal bool false ephemeris_celestial_body string Moon ephemeris_time_step celestial_magnitude_limit int float 6 6.0 celestial_category int 200 flag_horizontal_coordinates bool false Set to true to show the calculated ephemeris markers for Solar system bodies. Set to true to show the dates of calculated ephemeris for Solar system bodies. Set to true to show the magnitude of Solar system body for the calculated ephemeride. Set to true to use horizontal coordinates for ephemerides. Default celestial body for computation of ephemerides. Identificator for time step category. Value of limiting magnitude for the celestial objects in computation of their positions. Identificator for default category of celestial bodies. Set to true to use horizontal coordinates for compute of positions for the celestial objects. 1 Default value is D.1 Program Configuration D.1.3 275 flag_phenomena_opposition bool false phenomena_angular_separation float 1.0 phenomena_celestial_body string Venus phenomena_celestial_group int 0 wut_magnitude_limit float 10.0 wut_time_interval int 0 graphs_celestial_body graphs_first_id graphs_second_id string int int Moon 1 2  Set to true to compute of opposition phenomenon between the Solar system bodies. Allowed angular separation between celestial bodies for computation of phenomena. Default celestial body for computation of phenomena. Identificator for group of celestial bodies for computation of phenomenae. Value of limiting magnitude for calculations within What’s Up Tonight feature. Identificator for time interval within What’s Up Tonight feature computations. Default celestial body for draw of graphs. Identificator for left graph (blue line). Identificator for right graph (yellow line).  color This section defines the RGB colors for the various objects, lines, grids, labels etc. Values are given in float from 0 to 1. e.g. 1.0,1.0,1.0 for white, or 1,0,0 for red. Leave no whitespace between the numbers! ID Default Colour of the. . . default_color 0.5,0.5,0.7 default colour. daylight_text_color 0.0,0.0,0.0 info text at daylight. sky_background_color 0.0,0.0,0.0 sky background (non-black is useful for artists only). ecliptical_J2000_color ecliptic_J2000_color equinox_J2000_points_color solstice_J2000_points_color ecliptic_J2000_poles_color 0.4,0.1,0.1 0.7,0.2,0.2 0.7,0.2,0.2 0.7,0.2,0.2 0.7,0.2,0.2 ecliptical grid (J2000.0 frame). ecliptic line (J2000.0 frame). equinox points (J2000.0 frame). solstice points (J2000.0 frame). ecliptic poles (J2000.0 frame). ecliptical_color ecliptic_color equinox_points_color solstice_points_color ecliptic_poles_color precession_circles_color 0.6,0.3,0.1 0.9,0.6,0.2 0.9,0.6,0.2 0.9,0.6,0.2 0.9,0.6,0.2 0.9,0.6,0.2 ecliptical grid (of date). ecliptic line (of date). equinox points (of date). solstice points (of date). ecliptic poles (of date). precession circles. equator_J2000_color equatorial_J2000_color celestial_J2000_poles_color 0.2,0.2,0.6 0.1,0.1,0.5 0.2,0.2,0.6 equator line (J2000.0 frame). equatorial grid (J2000.0 frame). celestial poles (J2000.0 frame). equator_color equatorial_color celestial_poles_color 0.3,0.5,1.0 0.2,0.3,0.8 0.3,0.5,1.0 equator line (of date). equatorial grid (of date). celestial poles (of date). Appendix D. Configuration Files 276 circumpolar_circles_color 0.3,0.5,1.0 circumpolar circles. galactic_color galactic_equator_color galactic_poles_color 0.3,0.2,0.1 0.5,0.3,0.1 0.5,0.3,0.1 galactic grid. galactic equator line. galactic poles. supergalactic_color supergalactic_equator_color supergalactic_poles_color 0.2,0.2,0.2 0.4,0.4,0.4 0.4,0.4,0.4 supergalactic grid. supergalactic equator line. supergalactic poles. azimuthal_color horizon_color meridian_color prime_vertical_color zenith_nadir_color cardinal_color 0.0,0.3,0.2 0.2,0.6,0.2 0.2,0.6,0.2 0.2,0.5,0.2 0.2,0.6,0.2 0.8,0.2,0.1 azimuthal grid. horizon line. meridian line. prime vertical. zenith and nadir. cardinal points. colures_color 0.5,0.0,0.5 colures. longitude_color 0.2,0.4,0.4 opposition/conjunction longitude. asterism_lines_color asterism_names_color rayhelper_lines_color 0.4,0.4,0.8 0.4,0.4,0.8 1.0,1.0,0.0 asterism lines. asterism names. the ray helper lines. const_lines_color const_names_color const_boundary_color 0.2,0.2,0.6 0.4,0.6,0.9 0.3,0.1,0.1 constellation lines. constellation names. constellation boundaries. dso_label_color dso_circle_color 0.2,0.6,0.7 1.0,0.7,0.2 dso_galaxy_color dso_radio_galaxy_color dso_active_galaxy_color dso_interacting_galaxy_color dso_galaxy_cluster_color dso_quasar_color dso_possible_quasar_color dso_bl_lac_color dso_blazar_color dso_nebula_color dso_planetary_nebula_color dso_reflection_nebula_color dso_bipolar_nebula_color dso_emission_nebula_color dso_dark_nebula_color dso_hydrogen_region_color dso_supernova_remnant_color 1.0,0.2,0.2 0.3,0.3,0.3 1.0,0.5,0.2 0.2,0.8,1.0 0.2,0.5,1.0 1.0,0.2,0.2 1.0,0.2,0.2 1.0,0.2,0.2 1.0,0.2,0.2 0.1,1.0,0.1 0.1,1.0,0.1 0.1,1.0,0.1 0.1,1.0,0.1 0.1,1.0,0.1 0.3,0.3,0.3 0.1,1.0,0.1 0.1,1.0,0.1 deep-sky objects labels. deep-sky objects symbols, if not of the types below. galaxies symbols. radio galaxies symbols. active galaxies symbols. clusters of galaxies symbols. interacting galaxies symbols. quasars symbols. possible quasars symbols. BL Lac objects symbols. blazars symbols. nebulae symbols. planetary nebulae symbols. reflection nebulae symbols. bipolar nebulae symbols. emission nebulae symbols. dark nebulae symbols. hydrogen regions symbols. supernovae remnants symbols. D.1 Program Configuration 277 dso_supernova_candidate_color dso_supernova_remnant_cand_color 0.1,1.0,0.1 0.1,1.0,0.1 supernova candidates symbols. supernova remnant candidates symbols. interstellar matter symbols. clusters associated with nebulosity symbols. molecular clouds symbols. possible planetary nebulae symbols. protoplanetary nebulae symbols. star clusters symbols. open star clusters symbols. globular star clusters symbols. stellar associations symbols. star clouds symbols. star symbols. symbiotic star symbols. emission-line star symbols. emission objects symbols. young stellar objects symbols. dso_interstellar_matter_color dso_cluster_with_nebulosity_color 0.1,1.0,0.1 0.1,1.0,0.1 dso_molecular_cloud_color dso_possible_planetary_nebula_color dso_protoplanetary_nebula_color dso_cluster_color dso_open_cluster_color dso_globular_cluster_color dso_stellar_association_color dso_star_cloud_color dso_star_color dso_symbiotic_star_color dso_emission_star_color dso_emission_object_color dso_young_stellar_object_color 0.1,1.0,0.1 0.1,1.0,0.1 0.1,1.0,0.1 1.0,1.0,0.1 1.0,1.0,0.1 1.0,1.0,0.1 1.0,1.0,0.1 1.0,1.0,0.1 1.0,0.7,0.2 1.0,0.7,0.2 1.0,0.7,0.2 1.0,0.7,0.2 1.0,0.7,0.2 star_label_color planet_names_color planet_pointers_color planet_nomenclature_color 0.4,0.3,0.5 0.5,0.5,0.7 1.0,0.3,0.3 0.1,1.0,0.1 star labels. planet names. planet pointers. planetary nomenclature hints and labels. sso_orbits_color major_planet_orbits_color minor_planet_orbits_color dwarf_planet_orbits_color moon_orbits_color cubewano_orbits_color plutino_orbits_color sdo_orbits_color oco_orbits_color comet_orbits_color mercury_orbit_color venus_orbit_color earth_orbit_color mars_orbit_color jupiter_orbit_color saturn_orbit_color uranus_orbit_color neptune_orbit_color 0.7,0.2,0.2 0.7,0.2,0.2 0.7,0.5,0.5 0.7,0.5,0.5 0.7,0.2,0.2 0.7,0.5,0.5 0.7,0.5,0.5 0.7,0.5,0.5 0.7,0.5,0.5 0.7,0.8,0.8 0.5,0.5,0.5 0.9,0.9,0.7 0.0,0.0,1.0 0.8,0.4,0.1 1.0,0.6,0.0 1.0,0.8,0.0 0.0,0.7,1.0 0.0,0.3,1.0 default orbits. major planet orbits. minor planet orbits. dwarf planet orbits. moon of planet orbits. cubewano orbits. plutino orbits. scattered disk object orbits. Oort cloud object orbits. comet orbits. orbit of Mercury. orbit of Venus. orbit of Earth. orbit of Mars. orbit of Jupiter. orbit of Saturn. orbit of Uranus. orbit of Neptune. object_trails_color 1.0,0.7,0.0 planet trails. Appendix D. Configuration Files 278 D.1.4 D.1.5 custom_marker_color 0.1,1.0,0.1 custom marker. script_console_keyword_color 1.0,0.0,1.0 script_console_module_color 0.0,1.0,1.0 script_console_comment_color 1.0,1.0,0.0 script_console_function_color 0.0,1.0,0.0 script_console_constant_color 1.0,0.5,0.5 syntax highlight for keywords in the script console. syntax highlight for modules in the script console. syntax highlight for comments in the script console. syntax highlight for functions in the script console. syntax highlight for constants in the script console.   custom_selected_info You can fine-tune the bits of information to display for the selected object in this section. Set the entry to true to display it. ID Type Description flag_show_absolutemagnitude flag_show_altaz flag_show_catalognumber flag_show_distance flag_show_extra flag_show_hourangle flag_show_magnitude flag_show_name flag_show_radecj2000 flag_show_radecofdate flag_show_galcoord flag_show_supergalcoord flag_show_eclcoordj2000 flag_show_eclcoordofdate flag_show_type flag_show_size flag_show_constellation bool bool bool bool bool bool bool bool bool bool bool bool bool bool bool bool bool absolute magnitude for objects. horizontal coordinates for objects. catalog designations for objects. distance to object. extra info for object. hour angle for object. magnitude for object. common name for object. equatorial coordinates (J2000.0 frame) of object. equatorial coordinates (of date) of object. galactic coordinates (System II) of object. supergalactic coordinates of object. ecliptic coordinates (J2000.0 frame) of object. ecliptic coordinates (of date) of object. type of object. size of object. show 3-letter IAU constellation label.   custom_time_correction Stellarium allows experiments with ∆T . See 17.4.3 for details. D.1.6 ID Type Description coefficients ndot year [float,float,float] float int Coefficients a, b, c for custom equation of ∆T n-dot value for custom equation of ∆T Year for custom equation of ∆T   devel This section is for developers only. D.1 Program Configuration D.1.7 D.1.8 279 ID Type Description convert_dso_catalog bool convert_dso_decimal_coord bool Set to true to convert file catalog.txt into file catalog.dat. Default value: false. Set to true to use decimal values for coordinates in source catalog. Default value: true.   dso_catalog_filters In this section you can fine-tune which of the deep-sky catalogs should be selected on startup. ID Type Default Description flag_show_ngc flag_show_ic flag_show_m flag_show_c flag_show_b flag_show_sh2 flag_show_vdb flag_show_rcw bool bool bool bool bool bool bool bool true true true false false false false false flag_show_lbn flag_show_ldn flag_show_cr flag_show_mel flag_show_pgc flag_show_ced flag_show_ugc flag_show_arp flag_show_vv flag_show_pk flag_show_png bool bool bool bool bool bool bool bool bool bool bool false false false false false false false false false false false flag_show_snrg flag_show_aco bool bool false false New General Catalogue (NGC). Index Catalogue (IC). Messier Catalog (M). Caldwell Catalogue (C). Barnard Catalogue (B). Sharpless Catalogue (Sh-II). Van den Bergh Catalogue of reflection nebulae (VdB). The RCW catalogue of Hα-emission regions in the southern Milky Way. Lynds’ Catalogue of Bright Nebulae (LBN). Lynds’ Catalogue of Dark Nebulae (LDN). Collinder Catalogue (Cr). Melotte Catalogue of Deep Sky Objects (Mel). HYPERLEDA. I. Catalog of galaxies (PGC). Cederblad Catalog of bright diffuse Galactic nebulae (Ced). The Uppsala General Catalogue of Galaxies (UGC). Atlas of Peculiar Galaxies (Arp). The Catalogue of Interacting Galaxies (VV). The Catalogue of Galactic Planetary Nebulae (PK). The Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (PN G). A catalogue of Galactic supernova remnants (SNR G). A Catalog of Rich Clusters of Galaxies (ACO).   dso_type_filters In this section you can fine-tune which types of the deep-sky objects should be selected on startup. Appendix D. Configuration Files 280 D.1.9 ID Type Default Description flag_show_galaxies flag_show_active_galaxies flag_show_interacting_galaxies flag_show_clusters flag_show_bright_nebulae flag_show_dark_nebulae flag_show_planetary_nebulae flag_show_hydrogen_regions flag_show_supernova_remnants flag_show_galaxy_clusters flag_show_other bool bool bool bool bool bool bool bool bool bool bool true true true true true true true true true true true display galaxies. display active galaxies. display interacting galaxies. display star clusters. display bright nebulae. display dark nebulae. display planetary nebulae. display hydrogen regions. display supernovae remnants. display clusters of galaxies. display other deep-sky objects.   gui This section includes settings for the graphical user interface. ID Type Default Description flag_show_gui bool true If true, display GUI. base_font_size base_font_name int string 13 Verdana (Windows) DejaVu Sans (others) Sets the font size. Typical value: 15 Selects the name for base font base_font_file string flag_mouse_cursor_timeout bool true mouse_cursor_timeout float 10 flag_show_flip_buttons bool false Enables/disables display of the image flipping buttons in the main toolbar (see section 4.3.4) flag_show_nebulae_ background_button bool false Set to true if you want to have access to the button for enabling/disabling backgrounds for deep-sky objects flag_show_toast_survey_button bool false Set to true if you want to have access to the button for enabling/disabling Digitized Sky Survey for deep-sky objects selected_object_info string all Values: all, short, none, and custom (since V0.12.0; see 4.3.2). custom_marker_size float 5.0 Size of custom marker. Selects the name for font file, e.g. DejaVuSans.ttf Set to false if you want to have cursor visible at all times. Set to 0 if you want to keep the mouse cursor visible at all times. non-0 values mean the cursor will be hidden after that many seconds of inactivity D.1 Program Configuration 281 custom_marker_radius_limit int 15 Limit the click radius for mouse cursor position in any direction for removing of closest custom marker. auto_hide_horizontal_toolbar bool true auto_hide_vertical_toolbar bool true flag_use_window_transparency flag_show_buttons_background bool bool false true flag_show_datetime bool true flag_time_jd bool false flag_show_tz bool false flag_show_location flag_show_fps bool bool true true flag_show_fov bool true flag_fov_dms bool false Set to true if you want auto hide the horizontal toolbar. Set to true if you want auto hide the vertical toolbar. If false, show menu bars opaque If true, use background under buttons on bottom bar. display date and time in the bottom bar use JD format for time in the bottom bar show time zone info in the bottom bar display location in the bottom bar show at how many frames per second Stellarium is rendering show how many degrees your vertical field of view is use DMS format for FOV in the bottom bar flag_show_decimal_degrees bool false If true, use decimal degrees for coordinates flag_use_azimuth_from_south bool false If true, calculate azimuth from south towards west (as in some astronomical literature) flag_surface_brightness_arcsec bool false flag_surface_brightness_short bool false Toggle usage the measure unit mag / 0 (mag /arcmin2 ) or mag / 00   (mag /arcsec2 ) for the surface brightness of deep-sky objects. Toggle usage the short notation for the surface brightness of deep-sky objects. flag_enable_kinetic_scrolling bool true If true, use kinetic scrolling in the GUI2 . pointer_animation_speed float 1.0 Animation speed of pointers. gpsd_hostname string "localhost" gpsd_port int 2947 gps_interface string "COM3" hostname of server running gpsd (non-Windows only) port number of gpsd (non-Windows only) Port number of serial/USB GPS device (Windows only) 2 This option is available on Windows tablets only. Appendix D. Configuration Files 282 gps_baudrate D.1.10 D.1.11  int 4800 baudrate of serial/USB GPS device (Windows only)  init_location ID Type Description landscape_name string location last_location string string Sets the landscape you see. Built-in options are garching, geneva, grossmugl, guereins, hurricane, jupiter, mars, moon, neptune, ocean, saturn, trees, uranus, zero. Name of location on which to start stellarium. Coordinates of last used location in stellarium.   landscape ID Type Description atmosphere_fade_duration float flag_landscape bool flag_fog flag_atmosphere bool bool flag_landscape_sets_location bool minimal_brightness float atmosphereybin flag_minimal_brightness flag_landscape_sets_minimal_brightness int bool bool flag_enable_illumination_layer flag_enable_labels bool bool atmospheric_extinction_coefficient float temperature_C pressure_mbar cache_size_mb float float int Sets the time (seconds) it takes for the atmosphere to fade when de-selected Set to false if you don’t want to see the landscape at all Set to false if you don’t want to see fog on start-up Set to false if you don’t want to see atmosphere on start-up Set to true if you want Stellarium to modify the observer location when a new landscape is selected (changes planet and longitude/latitude/altitude if location data is available in the landscape.ini file) Set minimal brightness for landscapes. [0. . . 1] Typical value: 0.01 Set atmosphere binning coefficient for axis Y. Set to true to use minimal brightness for landscape. Set to true to use value for minimal brightness for landscape from landscape settings. Set to true to use illumination layer for landscape. Set to true to use landscape labels from gazetteer layer. Set atmospheric extinction coefficient k [mag/airmass] Set atmospheric temperature [Celsius] Set atmospheric pressure [mbar] Set the cache size for landscapes [megabytes]. Default: 100 D.1 Program Configuration D.1.12 D.1.13 D.1.14 283   localization ID Type Description sky_culture string sky_locale string app_locale string time_zone string time_display_format date_display_format string string Sets the sky culture to use. E.g. western, polynesian, egyptian, chinese, lakota, navajo, inuit, korean, norse, tupi, maori, aztec, sami. Sets language used for names of objects in the sky (e.g. planets). The value is a short locale code, e.g. en, de, en_GB Sets language used for Stellarium’s user interface. The value is a short locale code, e.g. en, de, en_GB. Sets the time zone. Valid values: system_default, or some region/location combination, e.g. Pacific/Marquesas time display format: can be system_default, 24h or 12h. date display format: can be system_default, mmddyyyy, ddmmyyyy or yyyymmdd (ISO8601).   main ID Type Description invert_screenshots_colors bool restore_defaults bool screenshot_dir version string string use_separate_output_file bool ignore_opengl_warning bool check_requirements bool If true, Stellarium will saving the screenshorts with inverted colors. If true, Stellarium will restore default settings at startup. This is equivalent to calling Stellarium with the –restore-defaults option. Path for saving screenshots Version of Stellarium. This parameter may be used to detect necessary changes in config.ini file, do not edit. Set to true if you want to create a new file for script output for each start of Stellarium Set to true if you don’t want to see OpenGL warnings for each start of Stellarium. Set to false if you want to disable and permanently ignore checking hardware requirements at startup. Expect problems if hardware is below requirements!   navigation This section controls much of the look&feel of Stellarium. Be careful if you change something here. ID Type Description preset_sky_time float startup_time_mode string flag_enable_zoom_keys bool Preset sky time used by the dome version. Unit is Julian Day. Typical value: 2451514.250011573 Set the start-up time mode, can be actual (start with current real world time), or Preset (start at time defined by preset_sky_time) Set to false if you want to disable the zoom Appendix D. Configuration Files 284 flag_manual_zoom bool flag_enable_move_keys flag_enable_mouse_navigation init_fov min_fov init_view_pos auto_move_duration mouse_zoom move_speed zoom_speed viewing_mode flag_manual_zoom auto_zoom_out_resets_direction time_correction_algorithm D.1.15 Set to false for normal zoom behaviour as described in this guide. When set to true, the auto zoom feature only moves in a small amount and must be pressed many times bool Set to false if you want to disable the arrow keys bool Set to false if you want to disable the mouse navigation. float Initial field of view, in degrees, typical value: ”60”. float Minimal field of view, in degrees, typical value: ”0.001389” (5"). floats Initial viewing direction. This is a vector with x,y,zcoordinates. x being N-S (S +ve), y being E-W (E +ve), z being up-down (up +ve). Thus to look South at the horizon use 1,0,0. To look Northwest and up at 45◦ , use -1,-1,1 and so on. float Duration (seconds) for the program to move to point at an object when the space bar is pressed. Typical value: 1.4 float Sets the mouse zoom amount (mouse-wheel) float Sets the speed of movement float Sets the zoom speed string If set to horizon, the viewing mode simulate an alt/azi mount, if set to equator, the viewing mode simulates an equatorial mount bool Set to true if you want to auto-zoom in incrementally. bool Set to true if you want to auto-zoom restoring direction. string Algorithm of DeltaT correction.   plugins_load_at_startup This section lists which plugins are loaded at startup (those with true values). Each plugin can add another section into this file with its own content, which is described in the respective plugin documentation, see 11. You activate loading of plugins in the F2 settings dialog, tab “Plugins”. After selection of which plugins to load, you must restart Stellarium. ID Type Description AngleMeasure ArchaeoLines CompassMarks MeteorShowers Exoplanets Observability Oculars Pulsars Quasars RemoteControl RemoteSync bool bool bool bool bool bool bool bool bool bool bool 12.1 Angle Measure plugin 13.9 ArchaeoLines plugin 12.2 Compass Marks plugin 13.6 Meteor Showers plugin 13.3 Exoplanets plugin 15.7 Observability Analysis 15.1 Oculars plugin 13.4 Pulsars plugin 13.5 Quasars plugin 12.7 Remote Control plugin 12.8 Remote Sync plugin D.1 Program Configuration Satellites SolarSystemEditor Supernovae TelescopeControl TextUserInterface Novae Scenery3dMgr D.1.16 D.1.17 bool bool bool bool bool bool bool 285 13.8 Satellites plugin 12.9 Solar System Editor plugin 13.2 Historical Supernovae plugin 15.2 Telescope Control plugin 12.6 Text User Interface plugin 13.1 Bright Novae plugin 14 Scenery 3D plugin   projection This section contains the projection of your choice and several advanced settings important if you run Stellarium on a single screen, multi-projection, dome projection, or other setups. ID Type Description type string Sets projection mode. Values: ProjectionPerspective, ProjectionEqualArea, ProjectionStereographic, ProjectionFisheye, ProjectionHammer, ProjectionCylinder, ProjectionMercator, ProjectionOrthographic, ProjectionMiller, or ProjectionSinusoidal. flip_horz flip_vert viewport bool bool string viewportMask viewport_fov_diameter viewport_x viewport_y viewport_width viewport_height viewport_center_x viewport_center_y viewport_center_offset_x viewport_center_offset_y string float float float float float float float float float How the view-port looks. Values: none (regular rectangular screen), disk (circular screen, useful for planetarium setup). How the view-port looks. Values: none. Usually 0. Usually 0. Usually half of viewport_width. Usually half of viewport_height. [-0.5. . . +0.5] Usually 0. [-0.5. . . +0.5] Use negative values to move the horizon lower.   proxy This section has setting for connection to network through proxy server (proxy will be using when host of proxy is filled). ID Type Description host_name type port user password string string int string string Name of host for proxy. E.g. Type of proxy. E.g. socks Port of proxy. E.g. 8080 Username for proxy. E.g. michael_knight Password for proxy. E.g. xxxxx Appendix D. Configuration Files 286 D.1.18 D.1.19 D.1.20   scripts ID Type Default Description startup_script string startup.ssc name of script executed on program start   search ID Type Description flag_search_online simbad_server_url flag_start_words coordinate_system bool string bool string If true, Stellarium will be use SIMBAD for search. URL for SIMBAD mirror If false, Stellarium will be search phrase only from start of words Specifies the coordinate system. Possible values: equatorialJ2000, equatorial, horizontal, galactic. Default value: equatorialJ2000.   spheric_mirror Stellarium can be used in planetarium domes. You can use a projector with a hemispheric mirror with geometric properties given in this section. Note: These functions are only rarely used or tested, some may not work as expected. ID Type Default Description flip_horz flip_vert projector_alpha bool bool float true false 0 projector_gamma float projector_delta float -1e100 projector_phi float 0 Flip the projection horizontally Flip the projection vertically This parameter controls the properties of the spheric mirror projection mode. This parameter controls the properties of the spheric mirror projection mode. This parameter controls the properties of the spheric mirror projection mode. This parameter controls the properties of the spheric mirror projection mode. projector_position_x projector_position_y projector_position_z mirror_position_x mirror_position_y mirror_position_z image_distance_div_height mirror_radius dome_radius custom_distortion_file texture_triangle_base_length zenith_y scaling_factor distorter_max_fov float float float float float float float float float string float float float float 0 1 -0.2 0 2 0 -1e100 0.25 2.5 viewportCenterWidth viewportCenterHeight float float 0.125 0.8 175.0 deprecated deprecated Set the maximum field of view for the spheric mirror distorter in degrees. Typical value: 180 projected image width, pixels projected image height, pixels D.1 Program Configuration viewportCenterX viewportCenterY D.1.21 287 float float projected image center X, pixels projected image center Y, pixels   stars This section controls how stars are rendered. D.1.22 ID Type Description relative_scale float absolute_scale float star_twinkle_amount flag_star_twinkle flag_forced_twinkle float bool bool flag_star_halo bool mag_converter_max_fov float mag_converter_min_fov float labels_amount init_bortle_scale float int relative size of bright and faint stars. Higher values mean that bright stars are comparitively larger when rendered. Typical value: 1.0 Changes how large stars are rendered. larger value lead to larger depiction. Typical value: 1.0 amount of twinkling. Typical value: 0.3 true to allow twinkling (but only when atmosphere is active!). true to allow twinkling stars even without atmosphere. This is obvious nonsense and contrary to nature, but some users seem to like it. false to not draw a halo around the brightest stars. This looks poor, but some users seem to prefer it. maximum field of view for which the magnitude conversion routine is used. Typical value: 90.0. minimum field of view for which the magnitude conversion routine is used. Typical value: 0.001. amount of labels. Typical value: 3.0 initial value of light pollution on the Bortle scale. Typical value: 3.   tui The built-in text user interface (TUI) plugin (see chapter 12.6) is most useful for planetariums. You can even configure a system shutdown command. For historical reasons, the section is not called [TextUserInterface] but simply [tui]. ID Type Default Description tui_font_size tui_font_color flag_show_gravity_ui float floatRGB bool 15 0.3,1,0.3 false flag_show_tui_datetime bool false flag_show_tui_short_obj_info bool tui_admin_shutdown_command string Font size for TUI. Font color for TUI. Enables or disables gravity mode for UI Set to true if you want to see a date and time label suited for dome projections set to true if you want to see object info suited for dome projections e.g. for Linux: shutdown –poweroff +2 Appendix D. Configuration Files 288 D.1.23 D.1.24   video ID Type Description fullscreen bool screen_w screen_h screen_x int int int screen_y int viewport_effect string minimum_fps int maximum_fps int If true, Stellarium will start up in full-screen mode, else windowed mode Display width when in windowed mode. Value in pixels, e.g. 1024 Display height when in windowed mode. Value in pixels, e.g. 768 Horizontal position of the top-left corner in windowed mode. Value in pixels, e.g. 0 Vertical position of the top-left corner in windowed mode. Value in pixels, e.g. 0 This is used when the spheric mirror display mode is activated. Values include none and sphericMirrorDistorter. Sets the minimum number of frames per second to display at (hardware performance permitting) Sets the maximum number of frames per second to display at. This is useful to reduce power consumption in laptops.   viewing This section defines which objects, labels, lines, grids etc. you want to see on startup. Set those to true. Most items can be toggled with hotkeys or switched in the GUI. ID Type Description flag_asterism_drawing flag_asterism_name flag_rayhelper_drawing flag_constellation_drawing flag_constellation_name flag_constellation_art flag_constellation_boundaries flag_constellation_isolate_selected bool bool bool bool bool bool bool bool flag_constellation_pick bool Display asterism line drawing Display asterism names Display the ray helper line drawing Display constellation line drawing Display constellation names Display constellation art Display constellation boundaries If true, constellation lines, boundaries and art will be limited to the constellation of the selected star, if that star is “on” one of the constellation lines. Set to true if you only want to see the line drawing, art and name of the selected constellation star flag_isolated_trails bool flag_isolated_orbits bool flag_azimutal_grid flag_equatorial_grid flag_equatorial_J2000_grid flag_ecliptic_grid flag_ecliptic_J2000_grid flag_galactic_grid flag_galactic_equator_line flag_equator_line bool bool bool bool bool bool bool bool Set to true if you only want to see the trail line drawn for the selected planet (asteroid, comet, moon) Set to true if you want to see orbits only for selected planet and their moons. Display azimuthal grid Display equatorial grid (of date) Display equatorial grid (J2000) Display ecliptic grid (of date) Display ecliptic grid (J2000) Display galactic grid (System II) Display galactic equator line Display celestial equator line (of date) D.1 Program Configuration D.1.25 289 flag_equator_J2000_line flag_ecliptic_line flag_ecliptic_J2000_line flag_meridian_line flag_prime_vertical_line flag_colure_lines flag_cardinal_points bool bool bool bool bool bool bool Display celestial equator line (J2000) Display ecliptic line (of date) Display ecliptic line (J2000) Display meridian line Display Prime Vertical line (East-Zenith-West) Display colure lines (Celestial Pole-à/ã/æ/é) Display cardinal points cardinal_font_size subcardinal_font_size flag_gravity_labels int int bool Font size for cardinal points. Typical value: 24 Font size for subcardinal points. Typical value: 18 Set to true if you want labels to undergo gravity (top side of text points toward zenith). Useful with dome projection. flag_moon_scaled moon_scale bool float Set to false if you want to see the real moon size Sets the moon scale factor, sometimes useful to correlate to our perception of the moon’s size. Typical value: 4 constellation_art_intensity float constellation_art_fade_duration float constellation_font_size constellation_line_thickness int int asterism_font_size asterism_line_thickness int int rayhelper_line_thickness int brightness [0. . . 1] of the constellation art images. Typical value: 0.5 time the constellation art takes to fade in or out, in seconds. Typical value: 1.5 font size for constellation labels thickness of lines of the constellations [1. . . 5]. Typical value: 1 font size for asterism labels thickness of lines of the asterisms [1. . . 5]. Typical value: 1 thickness of lines of the ray helpers [1. . . 5]. Typical value: 1 flag_night bool Enable night mode (red-only mode) on startup light_pollution_luminance float Sets the level of the light pollution simulation use_luminance_adaptation bool Enable dynamic eye adaptation.   DialogPositions By default, GUI panels appear centered in the screen. You can move them to your favorite location, and on next start they will appear on that location instead. The entries in this section define the upper left pixel coordinate where panels are stored. Examples: D.1.26 ID Type Example Description Help DateTime int,int int,int 58,39 1338,944 Position of Help panel Position of time panel   DialogSizes GUI panels can be resized by dragging on their lower corners or borders. Enlarged sizes are stored here, and on next start they will appear in this size. The entries in this section define the size. Examples: 0.15.1 Appendix D. Configuration Files 290 ID Type Example Description Help AstroCalc int,int int,int 895,497 913,493 Size of Help panel Size of AstroCalc panel   D.1.27 hips 0.18.0 This section defines the source list of the HiPS surveys, as well as other HiPS related options. ID Type Description show sources/size sources/n/url visible/url bool int string bool show HiPS at startup? Number of HiPS survey sources uri of the nth source hipslist file (n ∈ [1 . . . sources/size]) HiPS configured to be displayed. (Stores current setting on program exit) D.2 Solar System Configuration Files D.2 291 Solar System Configuration Files The files3 ssystem_major.ini and ssystem_minor.ini (in the data/ subdirectory of the program directory, contain orbital and rotational data from which Stellarium configures the Solar System objects. The minor bodies can be modified by placing a privately modified copy of ssystem_minor.ini into your own data/ directory (see Chapter 5). You can edit the file either manually, or with the Solar System Editor plugin (see Section 12.9). Each object’s data are described in its own section which is typically named after the object name. Some section names (e.g. those using diacriticals, spaces or other problematic characters) appear a bit mangled. We list here examples for the major planets, larger moons with special coordinate functions, minor moons with generic orbital elements, minor planets and comets with elliptical and parabolic orbit elements. All elements are stored in alphabetic order in the files, however it makes more sense to present the elements in another structure which better reflects the meaning. The actual order of the objects in the files, and order of entries inside an object section, is irrelevant. D.2.1 File ssystem_major.ini Planet section Example: [ jupiter ] name = Jupiter type = planet coord_func = jupiter_special albedo =0.51 atmosphere =1 color =1. , 0.983 , 0.934 tex_map = jupiter . png # texture courtesy of Bj \ xf6rn J \ xf3nsson halo = true oblateness =0.064874 orbit_v i su al iz a ti on _p e ri od =4331.87 parent = Sun radius =71492 rot_equ a to r_ as c en di ng _ no de = -22.203 rot_obliquity =2.222461 rot_periode =9.92491 rot_pole_de =64.49 rot_pole_ra =268.05 rot_rotation_offset = -1 # use JupiterGRS patch where name English name of the planet. May appear translated. type Mandatory for planets: parent =Sun. The body which this object is running around. Default: Sun coord_func The planet positions are all computed with a dedicated function (VSOP or DE43x). 3 Before v0.16, there was a single file, ssystem.ini, with slightly different rules. Appendix D. Configuration Files 292 orbit_visualization_period number of (earth) days for how long the orbit should be made visible. Typically Stellarium shows one orbit line. The orbit slowly drifts, however. atmosphere (0 or 1) flag to indicate whether observer locations should enable atmosphere drawing. radius Equator radius, km. oblateness Flattening of the polar diameter. (r pole /req ) albedo total albedo (reflectivity) of the planet. Used for “generic” magnitude computation, but the major planets usually have dedicated magnitude formulas, so the value is not evaluated unless you are observing from a location outside Earth. color Used to colorize halo. At least one of the components should be 1. tex_halo File name of texture map for halo texture in textures folder. (Used when zoomed out far enough so that the actual sphere is not visible.) tex_map File name of texture map in textures folder. halo Should be true to draw a halo (simple light disk) when object too small to draw a sphere. Elements for the Physical Ephemeris rot_equator_ascending_node deprecated rot_obliquity deprecated rot_pole_ra constant of axis right ascension in ICRF, degrees rot_pole_ra1 change per century of axis right ascension in ICRF, degrees rot_pole_de constant of axis declination in ICRF, degrees rot_pole_de1 change per century of axis declination in ICRF, degrees rot_rotation_offset longitude of central meridian at J2000.0. The special value here indicates special treatment for the Great Red Spot. rot_periode Duration of one sidereal rotation, in earth hours. rot_equator_ascending_node and rot_obliquity are the generic values to specify the axis orientation with respect to the parent object’s equator, or the VSOP87 inertial plane in case of planets. However, for planets the IAU has been using right ascension and declination of the pole in the ICRF for decades now. The elements to use for planets should therefore be the rot_pole_* values. In many cases, the attitude/rotation formula is given like α0 = rot_pole_ra + T ∗ rot_pole_ra1 (D.1) δ0 = rot_pole_de + T ∗ rot_pole_de1 (D.2) W = rot_rotation_offset + d ∗ rot_periode (D.3) These cases are covered by the data in ssystem_major.ini. Other cases are dealt with in a different way. Moon section All planet moons are defined only in ssystem_major.ini. Moons are special in that they orbit another planet. Therefore, the rotational elements used to be specified relative to the equatorial plane of the parent planet, and orbit_SemiMajorAxis are specified in kilometers. However, current IAU reference material gives axis orientation with right ascension and declination values for the pole in ICRF coordinates, with some of them in motion. So again, if one of the rot_pole_... values exist, we assume the current standard. For more complicated motion, again some special functions are applied. [ amalthea ] name = Amalthea type = moon parent = Jupiter iau_moon_number = JV D.2 Solar System Configuration Files 293 coord_func = ell_orbit orbit_AscendingNode =141.5521520794674 orbit_Eccentricity =0.006175744402949701 orbit_Epoch =2454619.50000 orbit_Inclination =0.3864576103404582 orbit_LongOfPericenter =245.4222355150120000 orbit_MeanLongitude =224.7924893552550000 orbit_Period =0.5016370462116355 orbit_SemiMajorAxis =181994.8658358799 orbit_v i su al iz a ti on _p e ri od =0.5016370462116355 radius =73 rot_equ a to r_ as c en di ng _ no de =213.7 rot_obliquity =15.5 rot_periode =12.039289109079252 rot_rotation_offset =235.50 albedo =0.06 color =1. , 0.627 , 0.492 halo = true tex_map = amalthea . png model = j5amalthea_MLfix . obj where name English name of planet moon. No number, just the name. May be translated. type moon parent English name of planet or parent body. iau_moon_number a short label (string) consisting of the planet’s initial and the moon’s Roman number in order of discovery. coord_func Must be ell_orbit for moons with orbital elements given, or _special for orbit_AscendingNode Ω orbit_Eccentricity e orbit_Epoch orbit_Inclination i [degrees] orbit_LongOfPericenter orbit_MeanLongitude orbit_Period [days] orbit_SemiMajorAxis a [km] orbit_visualization_period [days] Defaults to orbit_Period to show orbit as closed line. This is in fact only useful in case of special functions for positioning where orbit_Period is not given. radius Equator radius, km. oblateness Flattening of the polar diameter. (r pole /req ) rot_equator_ascending_node =213.7 TRY TO AVOID! rot_obliquity =15.5 TRY TO AVOID! rot_pole_ra constant of axis right ascension in ICRF, degrees rot_pole_ra1 change per century of axis right ascension in ICRF, degrees rot_pole_de constant of axis declination in ICRF, degrees v0.16.1 294 v0.16.0 Appendix D. Configuration Files rot_pole_de1 change per century of axis declination in ICRF, degrees rot_rotation_offset longitude of central meridian at J2000.0. rot_periode Duration of one sidereal rotation, in earth hours. For moons in bound rotation (which always show one face towards their parent planet), it is best to omit this value: it defaults to orbit_Period * 24. albedo total reflectivity [0..1] color for drawing halo (default: 1,1,1) halo [=true|false] to draw a simple diffuse dot when zoomed out. Default: true tex_map name of spherical texture map. Many moons have been mapped by visiting spacecraft! model (optional) name of a 3D model for a non-spherical body in the model subdirectory of the program directory. Solar System Observer Stellarium is great for excursions to the surface of any object with known orbital elements. Configuring a viewpoint away from a planet requires a special kind of location. The Solar System Observer has been provided as a neutral view location high above the North pole of the Solar System. It has been configured like this: [ solar_system_observer ] name = Solar System Observer parent = Sun albedo =0. color =0. , 0. , 0. halo = false hidden = true coord_func = ell_orbit orbit_AscendingNode =0 orbit_Eccentricity =0 orbit_Epoch =2451545.0 orbit_Inclination =90 orbit_LongOfPericenter =0 orbit_MeanLongitude =90 orbit_Period =70000000000 orbit_SemiMajorAxis =70000000000 radius =1. rot_obliquity =90 type = observer Note the inclination and mean longitude of 90 degrees, and that it is hidden and has no halo. Earth Observer This is another “observer” location. The Earth Observer has been provided as a neutral view location above the Northern hemisphere of the Earth. It has been configured like this: [ earth_observer ] name = Earth Observer parent = Earth albedo =0. color =0. , 0. , 0. halo = false hidden = true D.2 Solar System Configuration Files 295 coord_func = ell_orbit orbit_AscendingNode =0 orbit_Eccentricity =0 orbit_Epoch =2451545.0 orbit_Inclination =43 orbit_LongOfPericenter =0 orbit_MeanLongitude =90 orbit_Period =100000000000 orbit_SemiMajorAxis =1000000 radius =1. rot_obliquity =90 type = observer D.2.2 File ssystem_minor.ini Minor Planet section [4 vesta ] type = asteroid minor_planet_number =4 name = Vesta coord_func = comet_orbit parent = Sun orbit_ArgOfPericenter =151.19843 orbit_AscendingNode =103.85141 orbit_Eccentricity =0.0887401 orbit_Epoch =2457000.5 orbit_Inclination =7.14043 orbit_MeanAnomaly =20.86389 orbit_MeanMotion =0.27154465 orbit_SemiMajorAxis =2.3617933 orbit_v i su al iz a ti on _p e ri od =1325.46 color =1. , 1. , 1. halo = true oblateness =0.0 albedo =0.423 radius =280 absolute_magnitude =3.2 slope_parameter =0.32 tex_map = vesta . png model =4 vesta_21_MLfix . obj type can be asteroid, dwarf planet, cubewano, plutino, scattered disc object, Oort cloud object. With the exception of Pluto (which is included in ssystem_major.ini and cannot be changed), all positions for minor bodies are computed with the orbiting elements given in this way. Appendix D. Configuration Files 296 v0.16.0 Note that although all minor planets orbit the sun in an elliptical orbit, the coord_func=comet_orbit. However, it is more common for minor planets to specify epoch, mean anomaly and mean motion. Visual magnitude is modelled from absolute magnitude H and slope parameter G. Elements for rotational axis may be given just like for planets when they are known. It is recommended to use the modern specification (elements rot_pole_...). A few asteroids have been visited by spacecraft, and for many other asteroids visual observations of stellar occultations by asteroids and light curve measurements have enabled researchers to derive 3D shape models of asteroids. If a model is available in the models subdirectory of the program directory, this can be configured with a model entry. Comet section Comets are tiny, and their outgassing and close approaches to the major planets cause fast changes in their orbital elements, so that each apparition should be specified with a dedicated section in ssystem_minor.ini. The coord_func is always specified as comet_orbit. Note the specification of a time (JDE) at pericenter which is typical for comets. Comet brightness is evaluated from mag = absolute_magnitude+5·log distance+2.5·slope_parameter·log(CometSunDistance) (D.4) The term slope_parameter may be a misnomer in case of comets. From the literature (Meeus, 1998) (equation 33.13) we find mag = g + 5 log ∆ + κ log r (D.5) from which κ = 2 · slope_parameter. In any case, κ is typically [5. . . 15] and specific for each comet. albedo is used to set the brightness for rendering the body, if you are close enough. A large number of elements for historical comets is provided in the file ssystem_1000comets.ini in the installation directory. You can copy&paste what you need into your ssystem_minor.ini or add all with the Solar System Editor plugin (section 12.9). Unfortunately it is not possible to specify several sets of orbital elements for different epochs of one apparition which would allow automatic changes. Periodic Comet [1 phalley ] type = comet name =1 P / Halley coord_func = comet_orbit parent = Sun [ can be omitted ] orbit_ArgOfPericenter =111.7154 orbit_AscendingNode =58.8583 orbit_Eccentricity =0.968004 orbit_Inclination =162.2453 orbit_Peri cent erD ista nce =0.57136 orbit_TimeAtPericenter =2446463.12979167 orbit_good =780 D.2 Solar System Configuration Files 297 color =1.0 , 1.0 , 1.0 dust_brightnessfactor =1.5 dust_lengthfactor =0.4 dust_widthfactor =1.5 albedo =0.1 radius =5 absolute_magnitude =5.5 slope_parameter =3.2 tex_map = nomap . png model =1682 q1halley_MLfix . obj [ optional ] You may want to e.g. change the name in this entry to name=1P/Halley (1982i). Note a rather short duration of orbit_good, which means the comet is only displayed 780 days before and after perihel. Some comets have been visited by spacecraft so that shape models of their cores may be available and can be configured with a model entry. Parabolic/Hyperbolic Comet [ c2013us10 %28 catalina %29] type = comet name = C /2013 US10 ( Catalina ) coord_func = comet_orbit parent = Sun orbit_ArgOfPericenter =340.3533 orbit_AscendingNode =186.141 orbit_Eccentricity =1.000372 orbit_Inclination =148.8766 orbit_Peri cent erD ista nce =0.822958 orbit_TimeAtPericenter =2457342.20748843 orbit_good =1000 color =1.0 , 1.0 , 1.0 dust_brightnessfactor =1.5 dust_lengthfactor =0.4 dust_widthfactor =1.5 albedo =0.1 radius =5 absolute_magnitude =4.4 slope_parameter =4 tex_map = nomap . png This has basically the same format. Note eccentricity is larger 1, this means the comet is running on a slightly hyperbolic orbit. Stellarium shows data for this comet for almost 3 years (orbit_good=1000 days) from perihel. v0.16.0 E. Planetary nomenclature v0.17.0 Planetary nomenclature, like terrestrial nomenclature, is a system of uniquely identifying features on the surface of a planet or natural satellite so that the features can be easily located, described, and discussed. Since the invention of the telescope, astronomers have given names to the surface features they have discerned, especially on the Moon and Mars. To standardize planetary nomenclature, the International Astronomical Union (IAU) was assigned in 1919 the task of selecting official names for features on solar system bodies1 . Figure E.1: Feature nomenclature of the Moon. 1 History of Planetary Nomenclature – Appendix E. Planetary nomenclature 300 Since version 0.17.0 Stellarium supports planetary nomenclature, which allows using the planetarium for educational and informative purposes on the one hand, and as tool for recognition and targeting of the planetary features for advanced amateurs on the other hand, avoiding the need for additional cartographic software in the field. All planetary nomenclature items are stored in a dedicated internal format, and all names are translatable to provide better understanding of those names by average users and newbies – for example in schools or universities. Of course all nomenclature items are available for finding in the Search Tool after enabling the display of nomenclature (this feature is rather costly in terms of computing power and therefore is by default disabled in the GUI). The information in sections E.2–E.5, included here for reference, has been taken from the “Gazetteer of Planetary Nomenclature” website by the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN)2 . E.1 Format of nomenclature data file File data/nomenclature.fab is a plain text file in UTF-8 encoding and has a very simple data format: • One item per line; • Each item contains seven elements with white space (“space” or “tab” character) as delimiter. Item Type Comment planet name string ID of planetary feature integer translatable name of planetary feature string type of planetary feature string center latitude of planetary feature center longitude of planetary feature size of planetary feature float float float English name of the planet, moon or minor body carrying the named feature unique integer, equal to Feature ID obtained from Gazetteer of Planetary Nomenclature English name, containing context data for translators 2-char code (see designation column in table in section E.5) decimal degrees decimal degrees kilometers Example: Vesta 15201 _ ( " Caesonia " ," crater " ) AA 31.20117 249.93457 104.23 E.2 How names are approved by the IAU When images are first obtained of the surface of a planet or satellite, a theme for naming features is chosen and a few important features are named, usually by members of the appropriate IAU task group (a commonly accepted planet-naming group). Later, as higher resolution images and maps become available, additional features are named at the request of investigators mapping or describing specific surfaces, features, or geologic formations. Anyone may suggest that a specific name be considered by a task group. If the members of the task group agree that the name is appropriate, it can be retained for use when there is a request from a member of the scientific community that a specific feature be named. Names successfully reviewed by a task group are 2, visited on 2017-10-30 E.3 IAU rules and conventions 301 submitted to the IAU Working Group for Planetary System Nomenclature (WGPSN)3 . Upon successful review by the members of the WGPSN, names are considered provisionally approved and can be used on maps and in publications as long as the provisional status is clearly stated. Provisional names are then presented for adoption to the IAU’s General Assembly, which met triennially in the past, and which now adopts nomenclature for planetary surface features as required. A name is not considered to be official – that is, “adopted” – until the General Assembly has given its approval. E.3 IAU rules and conventions Names adopted by the IAU must follow various rules and conventions established and amended through the years by the Union. These include: 1. Nomenclature is a tool and the first consideration should be to make it simple, clear, and unambiguous. 2. In general, official names will not be given to features whose longest dimensions are less than 100 meters, although exceptions may be made for smaller features having exceptional scientific interest. 3. The number of names chosen for each body should be kept to a minimum. Features should be named only when they have special scientific interest, and when the naming of such features is useful to the scientific and cartographic communities at large. 4. Duplication of the same surface feature name on two or more bodies, and of the same name for satellites and minor planets, is discouraged. Duplications may be allowed when names are especially appropriate and the chances for confusion are very small. 5. Individual names chosen for each body should be expressed in the language of origin. Transliteration for various alphabets should be given, but there will be no translation from one language to another. 6. Where possible, the themes established in early solar system nomenclature should be used and expanded on. 7. Solar system nomenclature should be international in its choice of names. Recommendations submitted to the IAU national committees will be considered, but final selection of the names is the responsibility of the International Astronomical Union. Where appropriate, the WGPSN strongly supports an equitable selection of names from ethnic groups, countries, and gender on each map; however, a higher percentage of names from the country planning a landing is allowed on landing site maps. 8. No names having political, military or religious significance may be used, except for names of political figures prior to the 19th century. 9. Commemoration of persons on planetary bodies should not normally be a goal in itself, but may be employed in special circumstances and is reserved for persons of high and enduring international standing. Persons being so honored must have been deceased for at least three years, before a proposal may be submitted. 10. When more than one spelling of a name is extant, the spelling preferred by the person, or used in an authoritative reference, should be used. Diacritical marks are a necessary part of a name and will be used. 11. Ring and ring-gap nomenclature and names for newly discovered satellites are developed in joint deliberation between WGPSN and IAU Commission X2. Names will not be assigned to satellites until their orbital elements are reasonably well known or definite features have been identified on them. 3 Working Group for Planetary System Nomenclature – Appendix E. Planetary nomenclature 302 12. Accessible and authoritative sources, including Internet sources, are required for adopted names. Wikipedia is not sufficient as a source, but may be useful for identifying appropriate sources. In addition to these general rules, each task group develops additional conventions as it formulates an interesting and meaningful nomenclature for individual planetary bodies. Most of these conventions are self evident from study of the appendixes that follow. E.4 Naming conventions Names for all planetary features include a descriptor term, with a few exceptions. For craters, the descriptor term is implicit. Some features named on Io and Triton do not carry a descriptor term because they are ephemeral. In general, the naming convention for a feature type remains the same regardless of its size. Exceptions to this rule are channels (valles) on Mars and Venus, and craters on the Moon, Mars, and Venus; naming conventions for these features differ according to size. The categories for naming features on each planet or satellite (and the exceptions) are listed in Categories for Naming Features on Planets and Satellites4 . One feature classification, regio, was originally used on early maps of the Moon and Mercury (drawn from telescopic observations) to describe vague albedo features. It is now also used to delineate a broad geographic region. Named features on bodies so small that coordinates have not yet been determined are identified on drawings or images of the body that are included in the IAU Transactions volume of the year when the names were adopted. Satellite rings and gaps in the rings are named for scientists who have studied these features; drawings that show these names are also included in the pertinent Transactions volume. Names for atmospheric features are informal at present; a formal system will be chosen in the future. The boundaries of many large features (such as terrae, regiones, planitiae, and plana) are not topographically or geomorphically distinct; the coordinates of these features are identified from an arbitrarily chosen center point. Boundaries (and thus coordinates) may be determined more accurately from geochemical and geophysical data obtained by future missions. During active missions, small surface features are often given informal names. These may include landing sites, spacecraft impact sites, and small topographic features, such as craters, hills, and rocks. Such names will not be given official status by the IAU, except as provided for by Rule 2 above. As for the larger objects, official names for any such small features would have to conform to established IAU rules and categories. When a satellite has been discovered through the efforts of a large scientific team, the list of individual team members may be too long to include all contributors. In such cases, credit for the discovery will go to the science team. 4 Surface Feature Categories – E.5 Descriptor terms (feature types) E.5 303 Descriptor terms (feature types) Descriptor terms are intended to represent morphological characteristics, not geological origin. The WGPSN does not endorse any specific scientific hypotheses when assigning descriptors. Feature Designation Description Albedo Feature AL Geographic area distinguished by amount of reflected light Arc-shaped feature Radial-patterned features on Venus Arcus, arcūs Astrum, astra AR AS Catena, catenae Cavus, cavi CA CB Chaos, chaoses Chasma, chasmata Collis, colles Corona, coronae Crater, craters CH CM CO CR AA Chain of craters Hollows, irregular steep-sided depressions usually in arrays or clusters Distinctive area of broken terrain A deep, elongated, steep-sided depression Small hills or knobs Ovoid-shaped feature A circular depression Dorsum, dorsa DO Ridge Eruptive center ER Active volcanic centers on Io Facula, faculae Farrum, farra FA FR Flexus, flexūs FE Fluctus, fluctūs Flumen, flumina Fossa, fossae Fretum, freta FL FM FO FT Bright spot Pancake-like structure, or a row of such structures A very low curvilinear ridge with a scalloped pattern Flow terrain Channel on Titan that might carry liquid Long, narrow depression Strait, a narrow passage of liquid connecting two larger areas of liquid Insula, insulae IN Island (islands), an isolated land area (or group of such areas) surrounded by, or nearly surrounded by, a liquid area (sea or lake) Labes, labēs Labyrinthus, labyrinthi Lacuna, lacunae LA LB LU Lacus, lacūs LC Landing site name Large ringed feature Lenticula, lenticulae Linea, lineae LF LG LE LI Lingula, lingulae LN Landslide Complex of intersecting valleys or ridges Irregularly shaped depression on Titan having the appearance of a dry lake bed “Lake” or small plain; on Titan, a “lake” or small, dark plain with discrete, sharp boundaries Lunar features at or near Apollo landing sites Cryptic ringed features Small dark spots on Europa A dark or bright elongate marking, may be curved or straight Extension of plateau having rounded lobate or tongue-like boundaries Macula, maculae MA Dark spot, may be irregular Appendix E. Planetary nomenclature 304 Mare, maria ME Mensa, mensae Mons, montes MN MO “Sea”; on the Moon, low albedo, relatively smooth plain, generally of large extent; on Mars, dark albedo areas of no known geological significance; on Titan, large expanses of dark materials thought to be liquid hydrocarbons A flat-topped prominence with cliff-like edges Mountain Oceanus, oceani OC A very large dark area on the moon Palus, paludes Patera, paterae PA PE Planitia, planitiae Planum, plana Plume, plumes Promontorium, promontoria PL PM PU PR “Swamp”; small plain An irregular crater, or a complex one with scalloped edges Low plain Plateau or high plain Cryo-volcanic features on Triton “Cape”; headland promontoria Regio, regiones RE Reticulum, reticula Rima, rimae Rupes, rupēs RT RI RU Satellite Feature SF Scopulus, scopuli Serpens, serpentes SC SE Sinus, sinūs SI Sulcus, sulci SU A feature that shares the name of an associated feature. For example, on the Moon the craters referred to as “Lettered Craters” are classified in the gazetteer as “Satellite Features” Lobate or irregular scarp Sinuous feature with segments of positive and negative relief along its length “Bay”; small plain; on Titan, bays within seas or lakes of liquid hydrocarbons Subparallel furrows and ridges Terra, terrae Tessera, tesserae Tholus, tholi TA TE TH Extensive land mass Tile-like, polygonal terrain Small domical mountain or hill Unda, undae UN Dunes Vallis, valles Vastitas, vastitates Virga, virgae VA VS VI Valley Extensive plain A streak or stripe of color A large area marked by reflectivity or color distinctions from adjacent areas, or a broad geographic region Reticular (netlike) pattern on Venus Fissure Scarp Author and Acknowledgement The nomenclature feature has been implemented by Teresa Huertas Roldán supported by the “ESA Summer of Code in Space 2017” programme. F. Accuracy Stellarium originally was developed to present a beautiful simulation of the night sky, mostly to understand what is visible in the sky when you leave your house, i.e., for present times. To save computation time, some concessions were made in astronomical accuracy by using simplified models which seemed acceptable at that time. However, many users started to overstress Stellarium’s capabilities to simulate the historical sky of many centuries in the past, and found — or even worse: did not find, but simply published — the resulting inconsistencies and errors. Unfortunately, celestial motions are indeed more complicated than a simple clockwork, and the process of retrofitting detailed and accurate models which started around v0.11.0 is not completed yet. Therefore, when using Stellarium for scientific work like eclipse simulation to illustrate records found in Cuneiform tablets, always also use some other reference to compare, and of course specify the program version you used for your work. (The next version may be more accurate or at least provide different results!) You can of course contact us if you are willing and able to help improving Stellarium’s accuracy! F.1 Date Range The calendar dates are limited to a very wide interval of years, -100.000. . . 100.000. This is mostly useful to visualize the effect of stellar proper motions or the wobbling motion of Earth’s axis known as precession. If you observe the other planets, this is way beyond what current models are able to show! Observe for example the Moon: you will find that it seems to run on a polar orbit around +78.000 and even retrograde on a highly elongated orbit a few millennia after that. This is obvious nonsense, caused by extrapolating mathematical models in inappropriate ways. F.2 Stellar Proper Motion Even though you can follow stellar proper motion for tens of thousands of years, please note that the computation only takes the linear components ∆α, ∆δ into account. For times far from today, a true 3D computation would be required, so that also changes in distance (and thus, brighness) Appendix F. Accuracy 306 Object(s) Method Mercury, Venus, Earth-Moon barycenter, Mars Jupiter, Saturn VSOP87 Uranus, Neptune Pluto Earth’s Moon Galilean satellites Notes Accuracy is 1 arc-second from 2000 B.C. – 6000 A.D. VSOP87 Accuracy is 1 arc-second from 0 A.D. – 4000 A.D. VSOP87 Accuracy is 1 arc-second from 4000 B.C. – 8000 A.D. ? Pluto’s position is valid only from 1885 A.D. – 2099 A.D. ELP2000-82B Fit against JPL DE200, which provides date range 1850–2050. Positions should be usable for some (unspecified) longer interval. L2 Valid from 500 A.D. – 3500 A.D. Table F.1: Orbit-centric accuracy of used algorithms could be simulated. Still, the simulation here should give a good impression which close and/or fast stars will move over time, and thus how constellations become deformed. Note that due to the way the stars are stored in catalogs, zooming in on fast stars like Arcturus may even cease to display such stars when their original area in the sky is no longer in view. Also, binary stars seem to break apart because Stellarium does not store them as systems revolving about their combined center of gravity. F.3 Planetary Positions Stellarium uses the VSOP87 theory (P. Bretagnon and Francou, 1988) to calculate the positions of the planets over time. This is an analytical ephemeris modeled to match the numerical integration run DE200 from NASA JPL, which by itself gives positions for 1850. . . 2050. Its use is recommended for the years -4000. . . +8000. You can observe the sun leaving the “ecliptic of date” and running on the “ecliptic J2000” outside this date range. This is obviously a mathematical trick to keep continuity. Still, positions may be somewhat useful outside this range, but don’t expect anything reliable 50,000 years in the past! The optionally usable JPL DE431 delivers planet positions strictly for -13000. . . +17000 only, and nothing outside, but likely with higher accuracy. Outside of this range, positions from VSOP87 will be shown again. As far as Stellarium is concerned, the user should bear in mind the limits of the VSOP87 and other models (Table F.1). Accuracy values for VSOP87 are heliocentric as given by P. Bretagnon and Francou (1988). Note that Stellarium models light-time correction (if enabled), but does not yet model aberration of light. Therefore seasons’ beginnings are off by a few minutes. F.4 Minor Bodies Positions for the Minor Bodies (Dwarf Planets, Asteroids, Comets) are computed with standard algorithms found in astronomical text books. The generally used method of orbital elements allows to compute the positions of the respective object on an undisturbed Kepler orbit around the sun. F.5 Precession and Nutation 307 However, gravitational, and in the case of comets, non-gravitational (outgassing) disturbances slowly change these orbital elements. Therefore an epoch is given for such elements, and computation of positions for times far from this epoch will lead to positional errors. Therefore, when searching for asteroids or comets, always update your orbital elements (See section 12.9), and use elements with an epoch as close to your time of observation as possible! Stellarium does not simulate gravitational perturbances and orbital changes of minor bodies passing major planets. F.5 Precession and Nutation Since v0.14.0, Stellarium computes the orientation of earth’s axis according to the IAU2006 Precession in a long-time variant developed by Vondrák, Capitaine, and Wallace (2011), and IAU2000B Nutation (McCarthy and Luzum, 2003). This also now allows proper depiction of the changes in ecliptic obliquity and display of “instantaneous precession circles” around the ecliptic poles. These circles are indeed varying according to ecliptical obliquity. Nutation is only computed for about 500 years around J2000.0. Nobody could have observed it before 1609, and it is unclear for how long this model is applicable. F.6 Planet Axes Orientation for the other planets is still simplified. Future versions should implement modern IAU-approved models. F.7 Eclipses The moon’s motion is very complicated, and eclipse computations can be tricky. One aspect which every student of history, prehistory and archaeology should know but as it seems not every does, is at least a basic understanding of the irregular slow-down of earth’s rotation known as ∆T (see section 17.4.3). Eclipse records on cuneiform tablets go back to the 8th century BC, some Chinese records go back a bit further. Experts on Earth rotation have provided models for ∆T based on such observations. These are usually given as parabolic fit, with some recommended time span. Extrapolating parabolic fits to erratic curves too far into the past is dangerous, pointless and inevitably leads to errors or invalid results. Models differ by many hours (exceeding a whole day!) when applied too far in the past. This means, there was certainly an eclipse, and latitude will be OK, but you cannot say which longitude the eclipse was covering. The probability to have seen a total eclipse at a certain interesting location will be very small and should by itself not be used as positive argument for any reasonable statement. This is not a problem of Stellarium, but of current knowledge. To repeat, you may find a solar eclipse in the 6th millennium BC, but you cannot even be sure which side of Earth could observe it! WANTED: A model for ∆T that works in the Mesolithic! F.8 The Calendar Stellarium follows the widely accepted convention that dates before the Gregorian calendar reform are given in the Julian calendar, introduced by J ULIUS C AESAR in 46 BC. This calendar introduces a leap day every fourth year, which is a bit too much. If you want to show summer solstice in the year -2500, you will notice it is not on June 21st. This is not an error of Stellarium – the Gregorian reform had a reason! In prehistoric times, it may be more useful to work with solar ecliptic longitudes. For example, summer solstice is at λ = 90. 308 Appendix F. Accuracy J ULIUS C AESAR was assassinated in March 44 BC=-43 (see below). His simple 4-year leap rule was then misapplied by the high priests of Rome by adding a leap day every third year. AUGUSTUS fixed the calendar, and only 8 AD was the first correctly applied leap year as we know them. Be careful if you are working in Augustean times: Stellarium does not model these issues! Some authors (esp. for Mesoamerican dates) give dates in the proleptic Gregorian calendar (which means, they apply the Gregorian leap year rules before 1582). This is a convention, they may of course do that, but you must do the conversion to the Julian calendar to visualize the sky with Stellarium. Hopefully they also give Julian Day numbers (JD), you can use them with Stellarium. JD numbers are independent from calendar systems. Some have noted a difference of one between dates given as BC versus Stellarium’s negative years. 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In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements”. G.7 COLLECTIONS OF DOCUMENTS You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects. You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document. G.8 AGGREGATION WITH INDEPENDENT WORKS A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document. If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate. 314 G.9 Appendix G. GNU Free Documentation License TRANSLATION Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail. 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The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing. H. Acknowledgements H.1 Contributors When not listed as chapter authors, the following were the main contributors to the User Guide, mostly for versions before V0.15: Matthew Gates Primary author of the first User Guide (versions 0.9 to 0.12) Sky guide; exercise ideas Paul Robinson Andras Mohari Celestial sphere diagrams; numerous corrections Rudy Gobits, Dirk Schwarzhans Mac platform specifics Barry Gerdes Windows platform specifics Customisation of .fab files Documentation Maintainer up to V0.12 Sigma Japanese translation; many corrections Richard Powell Figure 18.3 (colour/magnitude diagram) is a modification of his diagram; he kindly granted permission for it to be distributed under the FDL Many spelling corrections John Twin Georg Zotti Lead author of the 0.15+ editions Alexander Wolf New layout, many contributions for the 0.15+ editions The rest of the Stellarium developer team You know who you are. . . :-) Additional material has been incorporated into the guide from sources that are published under the GNU FDL, including material from Wikipedia and the Astronomy book at Wikibooks. H.2 How you can help We especially welcome contributions, but also bug reports, feature requests and other feedback through the usual channels (trackers, forums and so on): 318 Appendix H. Acknowledgements Stellarium on Github Bug tracker Questions for Stellarium (FAQ) Feedback forum H.3 Technical Articles Stellarium would not look the same and work without these works from computer graphics and astronomy. The tone reproductor class The class mainly performs a fast implementation of the algorithm from Tumblin and Rushmeier (1993), with more accurate values from Devlin et al. (2002). The blue shift formula is taken from Jensen et al. (2000) and combined with the Scotopic vision formula from Larson, Rushmeier, and Piatko (1997). The skylight class The class governs sky colors and is a fast implementation of the algorithm by Preetham, Shirley, and Smits (1999). The skybright class The class governs physical sky brightness values based on Bradley Schaefer’s VISLIMIT.BAS basic source code (Schaefer, 1998). The basic sources are available on the Sky and Telescope web site (code “offered as-is and without support”). The ∆T calculations For implementation of calculation routines for ∆T we used the following sources: 1. ∆T webpage by Rob van Gent: deltat/deltat.htm 2. Five Millennium Canon of Solar Eclipses: -1900 to +3000 (Espenak and Meeus, 2006) ( 3. “On the system of astronomical constants” (Clemence, 1948) 4. “The rotation of the earth, and the secular accelerations of the sun, moon and planets” (Spencer Jones, 1939) 5. “Polynomial approximations for the correction delta T E.T.-U.T. in the period 18001975” (Schmadel and Zech, 1979) 6. “ELP 2000-85 and the dynamic time-universal time relation” (Borkowski, 1988) 7. “Empirical Transformations from U.T. to E.T. for the Period 1800-1988” (Schmadel and Zech, 1988) 8. “Historical values of the Earth’s clock error ∆T and the calculation of eclipses” (Morrison and F. R. Stephenson, 2004) with Addendum (Morrison and F. R. Stephenson, 2005) 9. “Polynomial approximations to Delta T, 1620-2000 AD” (Meeus and Simons, 2000) 10. Canon of Solar Eclipses -2003 to +2526 (Mucke and Meeus, 1983) 11. “The accelerations of the earth and moon from early astronomical observations” (Muller and F. R. Stephenson, 1975) 12. “Pre-Telescopic Astronomical Observations” (F. R. Stephenson, 1978) 13. “Long-term changes in the rotation of the earth - 700 B.C. to A.D. 1980” (F. R. Stephenson and Morrison, 1984) 14. “Long-Term Fluctuations in the Earth’s Rotation: 700 BC to AD 1990” (F. R. Stephenson and Morrison, 1995) 15. Historical Eclipses and Earth’s Rotation (F. Richard Stephenson, 1997) 16. Astronomical Algorithms (Meeus, 1998) 17. Astronomy on the Personal Computer (Montenbruck and Pfleger, 2000) 18. Calendrical Calculations (The Millennium Edition) (Reingold and Dershowitz, 2001) 19. ∆T webpage by V. Reijs: H.4 Included Source Code 319 Precession: “New precession expressions, valid for long time intervals” (Vondrák, Capitaine, and Wallace, 2011) with correction (Vondrák, Capitaine, and Wallace, 2012) Nutation: “An abridged model of the precession-nutation of the celestial pole” (McCarthy and Luzum, 2003) This model provides accuracy better than 1 milli-arcsecond in the time 1995-2050. It is applied for years 1500..2500 only. H.4 Included Source Code • Some computation of the sidereal time (sidereal_time.h/c) and Pluto orbit contains code from the libnova library (LGPL) by Liam Girdwood. • The orbit.cpp/h and solve.h files were directly borrowed from Celestia (Chris Laurel; GPL license). They have now evolved a bit. • Several implementations of IMCCE theories for planet and satellite movement by Johannes Gajdosik (MIT-style license, see the corresponding files for the license text) • The tesselation algorithms were originally extracted from the glues library version 1.4 by Mike Gorchak (SGI FREE SOFTWARE LICENSE B). • OBJ loader in the Scenery3D plugin based on glObjViewer (c) 2007 dhpoware • Parts of the code to work with DE430 and DE431 data files have been taken from Project Pluto (GPL license). • The SpoutLibrary.dll and header from the SpoutSDK version 2.005 available at http: // (BSD license). H.5 Data 1. The Hipparcos star catalog From ESA (European Space Agency) and the Hipparcos mission. ref. ESA, 1997, The Hipparcos and Tycho Catalogues, ESA SP-1200 http://cdsweb. 2. The solar system data mainly comes from IMCCE and partly from Celestia. 3. Polynesian constellations are based on diagrams from the Polynesian Voyaging Society 4. Chinese constellations are based on diagrams from the Hong Kong Space Museum 5. Egyptian constellations are based on the work of Juan Antonio Belmonte, Instituto de Astrofisica de Canarias 6. The Tycho-2 Catalogue of the 2.5 Million Brightest Stars Hog E., Fabricius C., Makarov V.V., Urban S., Corbin T., Wycoff G., Bastian U., Schwekendiek P., Wicenec A. Astron. Astrophys. 355, L27 (2000) 7. Naval Observatory Merged Astrometric Dataset (NOMAD) version 1 (http://www.nofs. Norbert Zacharias writes: “There are no fees, both UCAC and NOMAD are freely available with the only requirement that the source of the data (U.S. Naval Observatory) and original product name need to be provided with any distribution, as well as a description about any changes made to the data, if at all.” The changes made to the data are: • try to compute visual magnitude and color from the b,v,r values • compute nr_of_measurements = thenumbero f validb, v, rvalues • throw away or keep stars (depending on magnitude, nr_of_measurements, combination of flags, tycho2 number) • add all stars from Hipparcos (incl. component solutions), and tycho2+1st supplement • reorganize the stars in several brigthness levels and triangular zones according to position and magnitude 320 8. 9. 10. 11. Appendix H. Acknowledgements The programs that are used to generate the star files are called "MakeCombinedCatalogue", "ParseHip", "ParseNomad", and can be found in the util subdirectory in source code. The position, magnitudes, and proper motions of the stars coming from NOMAD are unchanged, except for a possible loss of precision, especially in magnitude. When there is no vmagnitude, it is estimated from r or b magnitude. When there is no b- or v- magnitude, the color B-V is estimated from the other magnitudes. Also proper motions of faint stars are neglected at all. Stellarium’s Catalog of Variable Stars based on General Catalog of Variable Stars (GCVS) version 2013Apr. Samus N.N., Durlevich O.V., Kazarovets E V., Kireeva N.N., Pastukhova E.N., Zharova A.V., et al., General Catalogue of Variable Stars (Samus+ 2007-2012) cat=B%2Fgcvs& Consolidated DSO catalog was created from various data: (a) NGC/IC data taken from SIMBAD Astronomical Database http://simbad.u-strasbg. fr (b) Distance to NGC/IC data taken from NED (NASA/IPAC EXTRAGALACTIC DATABASE) (c) Catalogue of HII Regions (Sharpless, 1959) taken from VizieR http://vizier. (d) H-α emission regions in the Southern Milky Way (Rodgers+, 1960) taken from VizieR (e) Catalogue of Reflection Nebulae (Van den Bergh, 1966) taken from VizieR http: // (f) Lynds’ Catalogue of Dark Nebulae (LDN) (Lynds, 1962) taken from VizieR http: // (g) Lynds’ Catalogue of Bright Nebulae (Lynds, 1965) taken from VizieR http:// (h) Catalog of bright diffuse Galactic nebulae (Cederblad, 1946) taken from VizieR (i) Barnard’s Catalogue of 349 Dark Objects in the Sky (Barnard, 1927) taken from VizieR (j) A Catalogue of Star Clusters shown on Franklin-Adams Chart Plates (Melotte, 1915) taken from NASA ADS (k) On Structural Properties of Open Galactic Clusters and their Spatial Distribution. Catalog of Open Galactic Clusters (Collinder, 1931). Taken from NASA ADS http: // (l) The Collinder Catalog of Open Star Clusters. An Observer’s Checklist. Edited by Thomas Watson. Taken from CloudyNights page/articles/cat/articles/the-collinder-catalog-updated-r2467 Cross-identification of objects in consolidated DSO catalog was maked with: (a) SIMBAD Astronomical Database (b) Merged catalogue of reflection nebulae (Magakian, 2003) http://vizier.u-strasbg. fr/viz-bin/VizieR-3?-source=J/A+A/399/141 (c) Messier Catalogue was taken from Wikipedia (includes morphological classification and distances) (d) Caldwell Catalogue was taken from Wikipedia (includes morphological classification and distances) Morphological classification and magnitudes (partially) for Melotte catalogue was taken from DeepSkyPedia H.6 Image Credits H.6 321 Image Credits All graphics are copyrighted by the Stellarium’s Team (GPL) except the ones mentioned below: • The “earthmap” texture was created by NASA (Reto Stockli, NASA Earth Observatory) using data from the MODIS instrument aboard the Terra satellite (Public Domain). See section H.6.1 for details. • Moon texture map was combined from maps by USGS Astrogeology Research Program, (; Public Domain, DFSG-free) and by Lunar surface textures from Celestia, based on Clementine data (Public Domain). • Saturn map and ring textures created by Björn Jónsson: “All the planetary maps available on these pages are publicly available. You do not need a special permission to use them but if you do then please mention their origin in your work [..]” • Jupiter map created by James Hastings-Trew from Cassini data. “The maps are free to download and use as source material or resource in artwork or rendering (CGI or real time).” • The Venus, Amalthea, Proteus, Iapetus and Phoebe maps and rings of Uranus and Neptune are from Celestia ( under the GNU General Purpose License, version 2 or any later version: – Venus is from Björn Jónsson and modified by RVS. – Amalthea is a shaded relief map by Phil Stooke, colored by Wm. Robert Johnston (, and further modified by Jens Meyer and Grant Hutchison. – The Proteus map is from Phil Stooke. – Triton is probably from David Seal’s site (see below), modified by Chris Laurel and Grant Hutchison. – Iapetus and Phoebe maps are from dr. Fridger Schrempp (t00fri). • Mercury map is produced by NASA from Messenger data (https://astrogeology.usgs. gov/search/map/Mercury/Messenger/Global/Mercury_MESSENGER_MDIS_Basemap_ BDR_Mosaic_Global_166m) and modified and colored by RVS. License: public domain. • Europa, Io and Callisto maps are created by John van Vliet from PDS data and modified by RVS. License: cc-by-sa. • Ganymede map is from USGS and modified by RVS. Public domain. • Tethys, Dione, Rhea, Enceladus and Mimas maps are created by NASA (CICLOPS team) from Cassini data, colored by RVS. Public domain. • Hyperion map created by John van Vliet from PDS data, modified by RVS. License: cc-by-sa. • Triton: Image selection, radiometric calibration, geographic registration and photometric correction, and final mosaic assembly were performed by Dr. Paul Schenk at the Lunar and Planetary Institute, Houston, Texas. Image data from Voyager 2 (NASA, JPL). Original texture has “white spots”, which was filled by Dizel777 ( forum/19-563-25069-16-1409101585). • Pluto map is produced by NASA from New Horizons data and colored by RVS. (Courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute, • Charon map is produced by NASA from New Horizons data and colored by RVS. (Courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute ( • All other planet maps from David Seal’s site:; see license in section H.6.2. • The fullsky milky way panorama has been created by Axel Mellinger, University of Potsdam, Germany. Further information and more pictures available from http://home. License: permission given to “Modify and re- 322 • • • • • • • Appendix H. Acknowledgements distribute this image if proper credit to the original image is given.” All messiers nebula pictures except those mentioned below from the Grasslands Observatory: “Images courtesy of Tim Hunter and James McGaha, Grasslands Observatory at http: //” License: permission given to “use the image freely” (including right to modify and redistribute) “as long as it is credited.” M31, and the Pleiades pictures come from Herm Perez: default.htm License: “Feel free to use these images, if you use them in a commercial setting please attribute the source.” Images of M8, M33, NGC253, NGC1499, NGC2244 from Jean-Pierre Bousquet Images of M1, M15, M16, M27, M42, M57, M97, NGC6946 from Stephane Dumont Images of M17, M44, NGC856, NGC884 from Maxime Spano Constellation art, GUI buttons, logo created by Johan Meuris (Jomejome) (jomejome(at) License: released under the Free Art License ( Icon created by Johan Meuris, License: Creative Commons Attribution-ShareAlike 3.0 Unported. The “earth-clouds” texture includes imagery owned by NASA. See NASA’s Visible Earth project at License: 1. The imagery is free of licensing fees 2. NASA requires that they be provided a credit as the owners of the imagery. The cloud texturing was taken from Celestia (GPL; • The folder icon derived from the Tango Desktop Project, used under the terms of the Creative Commons Attribution Share-Alike license. • Images of NGC281, NGC5139, NGC6543, NGC6960, NGC7023, NGC7317, NGC7319, NGC7320 from Andrey Kuznetsov, Kepler Observatory (http://kepler-observatorium. ru). License: Creative Commons Attribution 3.0 Unported. • Images of NGC891, NGC1333, NGC2903, NGC3185, NGC3187, NGC3189, NGC3190, NGC3193, NGC3718, NGC3729, NGC4490, NGC5981, NGC5982, NGC5985, NGC7129 from Oleg Bryzgalov ( License: Creative Commons Attribution 3.0 Unported. • Image of solar corona from eclipse 2008-08-01 and image of η Carinae by Georg Zotti License: Creative Commons Attribution 3.0 Unported. • Images of IC1805, IC1848, NGC6888 from Steve Tuttle ( • Images of IC4628, M20, M21, M47, NGC2467, IC2948, NGC3324, NGC3293, NGC7590, RCW158 from Trevor Gerdes ( • Images of IC2118, NGC1532 from users of Ice In Space ( au/). • Image of IC5146 from James A Weier. • Images of SMC, LMC (Magellanic Clouds) and ρ Oph from Albert Van Donkelaar. • Images of NGC55, NGC300, NGC1365, NGC3628, NGC4945, NGC5128, NGC6726, NGC6744, NGC6752, NGC6822, NGC7293, NGC2070 from Philip Montgomery (http: // • The Vesta and Ceres map was taken from USGS website https://astrogeology.usgs. gov/ and colored by RVS. License: public domain. • Images of NGC7318, NGC7331, M3, M13, M51, M63, M64, M74, M78, M81, M82, M96, M101, M105, Barnard 22, Barnard 142, Barnard 173, IC405, IC443, NGC1514, NGC1961, NGC2371, NGC2403, NGC246, NGC2841, NGC3310, NGC3938, NGC4559, NGC7008, NGC7380, NGC7479, NGC7635, Sh2-101 from Peter Vasey, Plover Hill Observatory H.6 Image Credits • • • • • • • • • • • • • • • • H.6.1 323 ( Image of IC434 from Marc Aragnou. Images of IC59, IC63, IC410, NGC2359, Sadr region from Carole Pope (https://sites. Images of NGC3690, NGC5257, NGC6050, IC883, UGC8335 and UGC9618 from NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. License: public domain; ( Images of NGC40, NGC4631, NGC4627, NGC4656, NGC4657 from Steven Bellavia. Images of Barnard Loop, IC342 from Sun Shuwei. License: public domain. Images of M77, Sh2-264, Sh2-308 from Wang Lingyi. License: public domain. Images of IC10 from Lowell Observatory ( License: public domain. Images of IC2177, NGC6334, NGC6357, Fornax Cluster from ESO/Digitized Sky Survey 2 ( License: Creative Commons Attribution 4.0 International. Images of NGC3603 from ESO/La Silla Observatory ( License: Creative Commons Attribution 4.0 International. Images of NGC4244 from Ole Nielsen. License: Creative Commons Attribution-Share Alike 2.5 Generic. Images of NGC7000 from NASA. License: public domain. Images of IC1396 from Giuseppe Donatiello. License: Creative Commons CC0 1.0 Universal Public Domain Dedication. Images of Sh2-155 from Hewholooks ( License: Creative Commons Attribution-Share Alike 3.0 Unported. Images of NGC4565 from Ken Crawford ( License: “This work is free and may be used by anyone for any purpose. If you wish to use this content, you do not need to request permission as long as you follow any licensing requirements mentioned on this page.” Images of Coma Cluster from Caelum Observatory (http://www.caelumobservatory. com/). License: Creative Commons Attribution-Share Alike 3.0 Unported. Images of NGC1316 from ESO ( License: Creative Commons Attribution 4.0 International. Full credits for “earthmap” texture Author: Reto Stockli, NASA Earth Observatory, rstockli(at) Address of correspondence: Reto Stockli ETH/IAC (NFS Klima) & NASA/GSFC Code 913 (SSAI) University Irchel Building 25 Room J53 Winterthurerstrasse 190 8057 Zurich, Switzerland Phone: +41 (0)1 635 5209 Fax: +41 (0)1 362 5197 Email: rstockli(at) URL:, Supervisors: Fritz Hasler and David Herring, NASA/Goddard Space Flight Center Funding: This project was realized under the SSAI subcontract 2101-01-027 (NAS5-01070) License: “Any and all materials published on the Earth Observatory are freely available for re-publication or re-use, except where copyright is indicated.” Appendix H. Acknowledgements 324 H.6.2 License for the JPL planets images From Unless otherwise noted, images and video on JPL public web sites (public sites ending with a address) may be used for any purpose without prior permission, subject to the special cases noted below. Publishers who wish to have authorization may print this page and retain it for their records; JPL does not issue image permissions on an image by image basis. By electing to download the material from this web site the user agrees: 1. that Caltech makes no representations or warranties with respect to ownership of copyrights in the images, and does not represent others who may claim to be authors or owners of copyright of any of the images, and makes no warranties as to the quality of the images. Caltech shall not be responsible for any loss or expenses resulting from the use of the images, and you release and hold Caltech harmless from all liability arising from such use. 2. to use a credit line in connection with images. Unless otherwise noted in the caption information for an image, the credit line should be “Courtesy NASA/JPL-Caltech.” 3. that the endorsement of any product or service by Caltech, JPL or NASA must not be claimed or implied. Special Cases: • Prior written approval must be obtained to use the NASA insignia logo (the blue “meatball” insignia), the NASA logotype (the red “worm” logo) and the NASA seal. These images may not be used by persons who are not NASA employees or on products (including Web pages) that are not NASA sponsored. In addition, no image may be used to explicitly or implicitly suggest endorsement by NASA, JPL or Caltech of commercial goods or services. Requests to use NASA logos may be directed to Bert Ulrich, Public Services Division, NASA Headquarters, Code POS, Washington, DC 20546, telephone (202) 358-1713, fax (202) 3584331, email bert.ulrich(at) • Prior written approval must be obtained to use the JPL logo (stylized JPL letters in red or other colors). Requests to use the JPL logo may be directed to the Television/Imaging Team Leader, Media Relations Office, Mail Stop 186-120, Jet Propulsion Laboratory, Pasadena CA 91109, telephone (818) 354-5011, fax (818) 354-4537. • If an image includes an identifiable person, using the image for commercial purposes may infringe that person’s right of privacy or publicity, and permission should be obtained from the person. NASA and JPL generally do not permit likenesses of current employees to appear on commercial products. For more information, consult the NASA and JPL points of contact listed above. • JPL/Caltech contractors and vendors who wish to use JPL images in advertising or public relation materials should direct requests to the Television/Imaging Team Leader, Media Relations Office, Mail Stop 186-120, Jet Propulsion Laboratory, Pasadena CA 91109, telephone (818) 354-5011, fax (818) 354-4537. • Some image and video materials on JPL public web sites are owned by organizations other than JPL or NASA. These owners have agreed to make their images and video available for journalistic, educational and personal uses, but restrictions are placed on commercial uses. To obtain permission for commercial use, contact the copyright owner listed in each image caption. Ownership H.6 Image Credits of images and video by parties other than JPL and NASA is noted in the caption material with each image. H.6.3 DSS From The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. The National Geographic Society - Palomar Observatory Sky Atlas (POSS-I) was made by the California Institute of Technology with grants from the National Geographic Society. The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation. The Oschin Schmidt Telescope is operated by the California Institute of Technology and Palomar Observatory. 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Index A C absolute magnitude . . . . . . . . . . . . . . . . . . . . 202 Adams, Douglas . . . . . . . . . . . . . . . . . . . . . . . 196 air mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 al-Majriti, Abu al-Qasim al-Qurtubi. . . . . .126 al-Saffar, Abu al-Qasim Ahmed Ibn-Abd Allah Ibn-Omar al Ghafiqi Ibn- . . . . . . . 125 al-Samh al-Mahri, Abu al-Qasim ’Asbagh ibn Muhammad ibn . . . . . . . . . . . . . . . 126 Almagest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 Andromeda Galaxy . . . . . . . . . . . . . . . . . . . . 233 apparent magnitude . . . . . . . . . . . . . . . . . . . . 202 apparent radiant . . . . . . . . . . . . . . . . . . . . . . . 133 ASCOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Atmospheric Extinction . . . . . . . . . . . . . . . . 219 Atmospheric Refraction . . . . . . . . . . . . . . . . 219 Augustus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 azimuth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 Caesar, Julius . . . . . . . . . . . . . . . . . . . . . 307, 308 cardinal points . . . . . . . . . . . . . . . . . . . . . . . . . 193 Celestial Equator . . . . . . . . . . . . . . . . . . . . . . 192 Celestial Poles . . . . . . . . . . . . . . . . . . . . . . . . . 192 Celestial Sphere. . . . . . . . . . . . . . . . . . . . . . . .191 Cervantes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Colure Equinoctial . . . . . . . . . . . . . . . . . . . . . . . . 195 Solstitial . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Coordinate System Ecliptical . . . . . . . . . . . . . . . . . . . . . . . . . 195 Equatorial . . . . . . . . . . . . . . . . . . . . . . . . . 193 Galactic . . . . . . . . . . . . . . . . . . . . . . . . . . 196 Horizontal . . . . . . . . . . . . . . . . . . . . . . . . 192 Copernicus, Nicolaus . . . . . . . . . . . . . . . . . . . 124 crossbow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 B Barnard’s Star . . . . . . . . . . . . . . . . . . . . . 206, 236 Bayer, Johann . . . . . . . . . . . . . . . . . . . . . . . . . 209 binoculars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Blazhko effect . . . . . . . . . . . . . . . . . . . . . . . . . 261 Bortle, John E. . . . . . . . . . . . . . . . . . . . . . . . . 247 Brahe, Tycho . . . . . . . . . . . . . . . . . . . . . 124, 195 brown dwarfs . . . . . . . . . . . . . . . . . . . . . . . . . . 211 D DE430 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 DE431 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 declination . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Deep-sky objects . . . . . . . . . . . . . . . . . . . . . . . . 27 double stars . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 dwarf stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 336 INDEX E K ecliptic . . . . . . . . . . . . . . . . . . . . . . . . . . . 194, 195 ecliptical latitude . . . . . . . . . . . . . . . . . . . . . . 195 ecliptical longitude . . . . . . . . . . . . . . . . . . . . . 195 equator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 equinox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Kopernik, Mikolaj . . . . . . . . . . . . . . . . . . . . . 124 L Lipperhey, Hans . . . . . . . . . . . . . . . . . . . . . . . 124 luminosity class . . . . . . . . . . . . . . . . . . . . . . . . 211 F FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 318 First Point of Aries . . . . . . . . . . . . . . . . . . . . . 194 First Point of Cancer . . . . . . . . . . . . . . . . . . . 195 First Point of Capricorn. . . . . . . . . . . . . . . . .195 Flamsteed, John . . . . . . . . . . . . . . . . . . . . . . . 209 G galactic latitude . . . . . . . . . . . . . . . . . . . . . . . . 196 galactic longitude . . . . . . . . . . . . . . . . . . . . . . 196 Galilei, Galileo . . . . . . . . . . . . . . . . . . . . . . . . 124 giants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 GPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 H Halley, Edmund . . . . . . . . . . . . . . . . . . . . . . . 215 Hammer, Ernst von . . . . . . . . . . . . . . . . . . . . . . 28 Handy Angles . . . . . . . . . . . . . . . . . . . . . 201, 233 Harriot, Thomas . . . . . . . . . . . . . . . . . . . . . . . 124 Herschel, John . . . . . . . . . . . . . . . . . . . . . . . . . 197 Hertzsprung, Ejnar . . . . . . . . . . . . . . . . . . . . . 211 Hierarchical Progressive Surveys . . . . . . . . . 95 Hipparchus . . . . . . . . . . . . . . . . . . . 195, 202, 210 Hypatia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 I IAU . . 105, 124, 199, 209, 214, 278, 299–302, 307 INDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 International Virtual Observatory Alliance . 95 J Janssen, Jacharias . . . . . . . . . . . . . . . . . . . . . . 124 Julian Day . . . . . . . . . . . . . . . . . . . . . . . . . 20, 197 Modified . . . . . . . . . . . . . . . . . . . . . . 20, 198 M M31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218, 233 Magellanic Cloud Large . . . . . . . . . . . . . . . . . . . . . . . . 217, 228 Small . . . . . . . . . . . . . . . . . . . . . . . . 217, 229 main sequence . . . . . . . . . . . . . . . . . . . . . . . . . 211 mathematical horizon . . . . . . . . . . . . . . . . . . 192 Mercator, Gerardus . . . . . . . . . . . . . . . . . . . . . . 28 meridian convergence . . . . . . . . . . . . . . . . . . 152 Messier, Charles . . . . . . . . . . . . . . . . . . . . . . . 217 meteor shower . . . . . . . . . . . . . . . . . . . . . . . . . 133 meteoroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Milky Way . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 Miller, Osborn Maitland . . . . . . . . . . . . . . . . . 28 N nadir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 NMEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Northern Ecliptical Pole . . . . . . . . . . . . . . . . 195 O obliquity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 obliquity of the ecliptic . . . . . . . . . . . . . . . . . 203 Opposition/Conjunction Line . . . . . . . . . . . 195 P parallax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 planetary nebulae . . . . . . . . . . . . . . . . . . . . . . 196 Pogson, Norman . . . . . . . . . . . . . . . . . . . . . . . 202 population index . . . . . . . . . . . . . . . . . . . . . . . 134 precession . . . . . . . . . . . . . . . . . . . 194, 195, 203 precession circles . . . . . . . . . . . . . . . . . . . . . . 195 Proper motion . . . . . . . . . . . . . . . . . . . . . . . . . 206 Ptolemy . . . . . . . . . . . . . . . . . . . . . . . . . . 195, 209 pulsars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 337 INDEX R radiant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Right ascension . . . . . . . . . . . . . . . . . . . . . . . . 194 Right Ascension/Declination . . . . . . . . . . . . 193 RTS2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 Russell, Henry Norris . . . . . . . . . . . . . . . . . . 211 S scintillation . . . . . . . . . . . . . . . . . . . . . . . . 27, 220 sidereal time . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 sky survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 spectral types . . . . . . . . . . . . . . . . . . . . . . . . . . 211 spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 super-giants . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 T time dragging . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 V VSOP87 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 W white dwarfs . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Z zenith . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 Zenithal Hourly Rate . . . . . . . . . . . . . . . . . . . 134

Source Exif Data:
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PDF Version                     : 1.5
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Page Count                      : 353
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Author                          : Georg Zotti and Alexander Wolf (editors)
Title                           : Stellarium User Guide
Subject                         : Stellarium is a multi-platform open-source desktop planetarium. This document describes version 0.15+ (2016)
Creator                         : LaTeX with hyperref package
Producer                        : pdfTeX-1.40.18
Keywords                        : Stellarium, Manual
Create Date                     : 2018:03:25 15:24:05+07:00
Modify Date                     : 2018:03:25 15:24:05+07:00
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