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Your Astro-Tech AT80ED refractor is usable for day and night
viewing, simply by adding a star diagonal and eyepiece. Any brand of
eyepiece can be used, from a 40mm for the lowest practical
magnification (14x), to a 3mm (187x) for high power use. The 2"
accessory holder on the focuser drawtube and the supplied 1.25"
eyepiece adapter let you use either a 1.25" or 2" star diagonal and
eyepieces with no other adapter needed.
Your AT80ED's focal length is ideal for low to medium power wide-
angle views of nebulas, open star clusters, large galaxies, and comets.
Crisp views of the Moon, planets, binary stars, and globular clusters
are routine at powers of 112x to 187x 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 5mm eyepiece in your AT80ED
will give you a magnification of 112x (560mm/5mm = 112).
Astronomical Observing: The theoretical maximum usable power
available from your AT80ED is 187x, although this requires a 3mm
eyepiece that provides a narrow and very dim 0.43mm exit pupil. A
more practical maximum magnification for astronomical viewing with
your AT80ED would be 140x, 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 187x.
Under less than ideal conditions, lower powers in the 80x to 112x
range provide more consistently usable and pleasing images.
The widest possible field of view with a 1.25" eyepiece is about 3°,
which can be achieved with a 14x (40mm) Plössl eyepiece.
While your AT80ED 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 your diagonal in the most comfortable observing
position. To rotate the focuser, loosen the knurled lock ring on the
telescope barrel by turning it counterclockwise. Adjust the focuser to
the desired angle, then turn the lock ring back in the opposite direction
to lock the focuser at the new angle.
Terrestrial Observing: Your AT80ED works well for birding, nature
studies, sweeping the landscape from the home with a view, etc. It is
also a very good 560mm (11x) f/7 telephoto lens for terrestrial
photography. Generally speaking, the maximum usable daytime power
with any terrestrial scope is about 1x per mm of aperture (80x with a
7mm eyepiece on your AT80ED). 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 28x (20mm) to 62x (9mm) eyepiece is usually more
satisfying for everyday terrestrial use than an 80x eyepiece.
Mounting Your AT80ED: A stable tripod, altazimuth mount, or
German equatorial astronomical mount is essential for best viewing.
The scope's split tube rings will mount directly onto many German
equatorial mounts. The removable 8" long dovetail attached to the
rings has a 1/4"-20 thread hole for mounting on a sturdy photo tripod.
This Vixen-style dovetail also fits directly into the dovetail slot on
Astro-Tech Voyager altazimuth mounts; on Celestron Advanced Series
or Meade LXD-75 go-to mounts; or on Vixen Porta altazimuth, Sphinx
go-to, or Great Polaris German equatorial mounts.
Installing an Optional Finder: There are two threaded holes for
mounting an optional finder, such as the Astro-Tech #ATF illuminated
multiple reticle finder. They are at the 10 o'clock and 2 o'clock positions
on the top of the focuser, 3/4" behind the focuser rotation locking
collar. The holes have screwdriver-slotted inserts to keep dust out of
the scope. Please carefully note the position of the finder mounting
holes in the illustration on the front page. There are also two hex-
head inserts immediately behind the finder mounting holes. Do not
loosen these hex-head inserts, as they are for factory adjustments of
the focuser mechanism only. Undoing them will void your warranty.
Other Optional Astro-Tech Accessories: Astro-Tech makes 1.25"
and 2" star diagonals with state-of-the-art 99% reflectivity dielectric
astro-tech
from Astronomy Technologies, 680 24th Avenue SW, Norman, OK 73069
© 2008 by Astronomy Technologies
coatings to complement the performance of your AT80ED. These
diagonals are available from your Astro-Tech dealer to provide the
maximum possible brightness and planetary detail. A 45° viewing
image-erecting 1.25" diagonal is also available for terrestrial observing.
Caring for Your Scope Optics: Never store your scope 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 camera stores) in with the
telescope to absorb excess moisture, but do not put them in direct
contact with the lens. If not properly stored in a humid environment,
the telescope may develop mildew which can damage the optics.
If dew has formed on your scope after a night of observing, allow
the scope optics to air dry at room temperature before putting the
lens cover on your scope and storing it away.
If your 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 your 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: The AT80ED uses an automotive-
grade paint and anodized components. These very durable surfaces
can become smudged with fingerprints during use, but these will not
harm the finish. 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 remove the fingerprints. 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 your telescope in the rain or in conditions where it may
get wet. Your telescope is not waterproof. If your scope accidentally
gets caught in the rain, immediately wipe off all water using a clean
and dry soft cloth. If your 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 AT80ED 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.
www.astronomytechnologies.com
Specifications, features, and descriptions are effective 6/1/2008, but are subject to correction and/or modification without notice and/or obligation.
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