AT66ED Manual.pmd Astro Tech AT66 Manual

User Manual: Astro-Tech AT66ED

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Thank you for choosing this Astro-Tech AT66ED high-

quality compact apochromatic refractor.

While some observers might doubt that apochromatic

performance can be had in a 66mm scope that costs as little

as the AT66ED, we can say only that seeing is believing.

The images from its 400mm f/6 ED (Extra-low Dispersion

glass element) air-spaced doublet optics are virtually color-

free, even at high magnifications. At its low price, we believe

Aperture ................................................... 66mm (2.6”)

Focal Length .................................................... 400mm

Focal Ratio ...............................................................f/6

Objective Type .... air-spaced doublet with ED element

Optical Coatings................................ fully multicoated

Resolving Power (Dawes’ Limit) ...... 1.75 arc seconds

Visual Limiting Magnitude .................. 11.6 maximum

Light Grasp (versus the eye) ................................. 89x

Field Stops .... 10 glare-reducing baffles in optical tube

Focuser ............................... dual-speed Crayford-type

with 11:1 reduction ratio fine focus;

360° rotating camera angle/observing angle adjuster;

and thread-on 1.25” compression ring eyepiece holder

Focuser Travel ......................................... 2.4” (60mm)

with millimeter scale on drawtube for repeatable focus

Lens Shade ................................................. retractable

you’ll find that the optical performance of your AT66ED is

little short of astonishing.

This instruction manual will provide you with information

on how to get the most out of your new telescope, and how

to properly maintain your telescope so it can give you a

lifetime of observing enjoyment.

Please familiarize yourself with your telescope’s parts and

functions before operating it for the first time.

Astro-Tech AT66ED Apochromatic Refractor Specifications

Objective Lens Cover............................. slip-on metal

Tripod Mount ... removable combination L-bracket and

dovetail with 1/4”-20 thread mounting holes for photo

tripod use as well as direct mounting on Celestron,

Meade, and Vixen German equatorial mounts

Tube Diameter............................................ 75mm o. d.

Tube Length (lens shade retracted) ..... 11.5” (292mm)

Tube Length (lens shade extended) ..... 14.4” (366mm)

Optical Tube Weight ............................ 3.9 lbs. (1.8 kg)

Case .................................. aluminum-frame foam-fitted

lockable hard case, with carrying handle

Case Dimensions ............................. 15” x 9.5” x 6.25”

Lowest Usable Power ........ 10x (with 40mm eyepiece)

Highest Terrestrial Power ... 67x (with 6mm eyepiece)

Highest Practical Power.... 100x (with 4mm eyepiece)

Theoretical Maximum ........ 133x (with 3mm eyepiece)

Retractable dew shield

Lock knob

for focuser drawtube

underneath body

Locking collar for 360°

rotatable focuser

1/4”-20 thread

tripod mounting holes

in base of bracket

Combined equatorial mount

dovetail and L-bracket

tripod mounting shoe

PARTS OF THE AT66ED

Left coarse

focus knob

Fine

focus

knob

Focusing

scale on

focuser

drawtube

Thread-on 1.25”

eyepiece

adapter

1.25” eyepiece

lock knob

Dust cover

1.25” eyepiece

lock knob

Brass compression ring

Right

coarse

focus

knob

Thread-on

1.25”

eyepiece

adapter

Mounting point for

optional finder

Dust

cap

astro-tech AT66ED

from Astronomy Technologies

astro -tech

www.astronomytechnologies.com

from Astronomy Technologies, PO Box 720013, Norman, OK 73070

© 2006 by Astronomy Technologies Specifications, features, and descriptions are effective 4/1/2006, but are subject to correction and/or modification without notice and/or obligation.

Your Astro-Tech AT66ED refractor is usable for day and night

viewing, simply by adding a 1.25” star diagonal and eyepiece. Any

brand of 1.25” eyepiece can be used, from a 40mm for the lowest

possible magnification (10x), down to a 3mm (133x) for high power

use. Removing the Astro-Tech’s 1.25” eyepiece holder reveals a

Schmidt-Cassegrain rear cell thread on the focuser drawtube, allowing

you to add a thread-on SCT-type 2” diagonal for 2” eyepiece use.

The focal length of the AT66ED is ideal for low to medium power

wide-angle views of nebulas, open star clusters, large galaxies, and

comets. Crisp views of the Moon and planets are also routine at

magnifications of 100x to 133x when seeing conditions permit.

To calculate the magnification of your telescope and eyepiece

combination, divide the telescope focal length in mm by the eyepiece

focal length in mm. For example, a 4mm eyepiece in the AT66ED will

give you a magnification of 100x (400mm/4mm = 100).

Astronomical Observing: The theoretical maximum usable power

available from this telescope is 133x, although this requires a 3mm

eyepiece that provides a narrow and dim 0.5mm exit pupil. A more

practical maximum magnification for astronomical viewing with the

AT66ED would be 100x, using a 4mm eyepiece. Keep in mind that

seeing conditions play an important role in how high a magnification

you can use on any given night. Only very good seeing conditions

(clear skies and calm air) will support viewing at 133x. Under less

than ideal conditions, lower powers in the 65x to 100x range provide

more consistently usable and pleasing images.

The widest possible field of view with a 1.25” eyepiece is about

4.2°, which can be achieved with a 10x (40mm) Plössl eyepiece.

While the AT66ED has not been specifically designed for astro-

photography, it does an outstanding job as a wide-field astrograph

for casual 35mm and CCD imaging. A chrome thumbscrew under the

focuser lets you lock in a sharp focus for photography.

The focuser can be rotated a full 360° for the best photographic

composition, or to put the star diagonal in the most comfortable

observing position. Loosening the knurled lock ring on the scope

barrel by turning it counterclockwise lets you rotate the focuser. Turning

the ring back clockwise locks the focuser at the chosen angle.

Terrestrial Observing: The AT66ED works well for daytime birding,

nature studies, sweeping the landscape from the home with a view,

etc. It is also a very good 400mm (8x) f/6 telephoto lens for terrestrial

photography. Generally speaking, the maximum usable daytime power

with any terrestrial scope is about 1x per mm of aperture (67x with

the AT66ED). Attempts to push the daytime power beyond this point

often magnify the heat waves, dust, and “mirage” in our atmosphere

to the point where the images become blurry and unusable. A 40x

(10mm) to 50x (8mm) eyepiece is usually more satisfying for everyday

high power terrestrial use than an 80x eyepiece.

Mounting the AT66ED: A stable tripod or astronomical mount is

essential for best viewing. The AT66ED is light enough to be used on

any good quality camera tripod with a 7 to 8 pound payload capacity.

The scope’s L-shaped mounting foot has two 1/4”-20 thread holes

for direct connection to a standard photo tripod head. The front

mounting hole provides a better balance when the scope is used

with a 1.25” star diagonal and eyepiece. The rear mounting hole

provides a better balance when the scope is used with a heavier 2”

diagonal and eyepiece, or a camera.

The L-bracket is shaped like the dovetail used to connect optical

tubes to the Celestron CG-5 Advanced Series, Meade LXD-75, and

Vixen Sphinx and Great Polaris German equatorial mounts. This

allows you to install the AT66ED directly on any of these mounts with

no other adapter required.

Optional Astro-Tech Accessories: Astro-Tech makes a 1.25” star

diagonal with state-of-the-art 99% reflectivity dielectric coatings that

nicelt complements the performance of the AT66ED. This diagonal is

available from your Astro-Tech dealer to provide the maximum

reflectivity and planetary detail contrast possible. An Astro-Tech 45°

viewing angle image-erecting 1.25” diagonal is available for terrestrial

observing. An inexpensive Astro-Tech non-magnifying multi-reticle

illuminated finder is also available for your AT66ED.

Caring for Your Scope Optics: Never store the telescope in a

damp or humid environment. Avoid leaving it in a hot environment

(exposed to direct sunlight on a window sill, in a car trunk, etc.) If you

must store it in high humidity conditions, put a few packets of desiccant

(silica gel or the equivalent, available from most camera stores) in

with the telescope to absorb excess moisture. If not properly stored

in a humid environment, the telescope may develop mildew which

can damage the optics.

If dew has formed on the scope after a night of observing, allow

the scope optics to air dry at room temperature before putting the

lens cover on the scope and storing it away.

If the front lens surface becomes dusty, smeared, or shows

fingerprints or any other surface build-up, clean the lens as follows.

First, gently blow away any surface dust or particles with a clean air

blower (a child’s ear syringe or a photographer’s camel’s hair brush

with attached blower bulb, for example). Using canned or compressed

air is not recommended, as the propellant in the can may spit out and

leave difficult-to-remove deposits on the lens. Also, the expanding

compressed air drops in temperature as it leaves the can. The cold

air coming out of the tiny tube that most compressed air cans use to

direct the air flow has been known to chill a lens to the point of cracking

the glass if pointed at the same spot on the glass for too long.

Second, moisten a cloth with a few drops of a photographic-quality

optical cleaning solution designed for multicoated camera and

binocular lenses. A well-worn cotton handkerchief works well and

Zeiss and Kodak both make suitable fluids. Do not drip the cleaning

fluid directly on the lens. Use the barely damp (not wet) cloth to gently

wipe the lens surface clean, turning the cloth frequently to always

keep a clean portion of the cloth in contact with the lens. Blot the lens

dry with a dry portion of the cleaning cloth or a separate cloth. Start

with a clean cloth each time cleaning is needed.

Avoid overcleaning your scope. The multicoatings on the lens are

quite hard and durable. However, frequent overzealous cleaning can

scratch the coatings if all the dust particles (which are often tiny

flecks of windborne rock) are not removed before you start pushing a

damp cloth around the lens surface. A few specks of debris on the

lens will not be visible in your images, as they are not in the focal

plane and don’t block enough light to measure, let alone be seen.

Clean your optics only when absolutely necessary. If you take proper

care of your scope, cleaning should rarely be needed.

Caring for Your Scope Finish: Depending on the tube color, the

AT66ED is either fully anodized or finished in a combination of durable

paint and a liquid-anodize high gloss finish. The painted surfaces will

rarely show dirt or fingerprints. If they do, a clean soft cloth slightly

dampened with plain water should be enough to clean them.

The very durable anodized surfaces can be easily smudged with

fingerprints, but these will not harm the anodized finish. As with the

painted areas, a clean soft cloth slightly dampened with plain water

(or a little moisture from your breath and a quick wipe with a clean

handkerchief) is generally enough to clean the surface. Avoid harsh

chemical cleaners or organic solvents like benzene, alcohol, etc., as

these may ruin the finish. They can certainly affect the optical coatings

if they accidentally drip or splash on the objective lens.

Never use the telescope in the rain or in conditions where it may

get wet. The telescope is not waterproof. If the telescope accidentally

gets caught in the rain, immediately wipe off all water using a clean

and dry soft cloth. If the telescope gets totally soaked in water, or

submerged, immediately contact your dealer for service instructions.

Do not disassemble or attempt to repair your telescope yourself, as

this violates the warranty terms under the limited product warranty,

and negates any guarantee.

Caution! Never directly view the Sun with your telescope! Never

aim your AT66ED at the Sun without having a professionally-

manufactured solar filter mounted over the objective lens. Viewing

the Sun through the scope without the proper protection for even a

moment may result in permanent severe damage to your eyes, and

can even cause blindness. Contact your Astro-Tech dealer if you are

interested in purchasing a compatible professional solar filter.