Astro-Tech AT80EDT f/6 ED Triplet Refractor OTA

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This new Astro-Tech AT80EDT refractor has:

• 80mm f/6 fully multicoated triplet apochromatic optics using an ED center element 
• a dual-speed 2.5” rack-and-pinion focuser with 10:1 ratio fine focusing 
• a 2" dielectric-coated 99% reflectivity star diagonal with 2" and 1.25" compression ring eyepiece holders
• a camera angle adjuster 
• retractable lens shade/dew shield
• dual hinged split tube rings with a Vixen-style dovetail 

    For grab-and-go observing, Milky Way star field sweeping, and wide field astrophotography (as well an terrestrial observing and photography), many observers swear by a good fast focal ratio 80mm refractor. The 6.5 pound 80mm f/6 Astro-Tech AT80EDT ED triplet apo refractor is just that scope. It does it all.   

    The Astro-Tech AT80EDT’s slow-polished triplet optics, ED glass center element, and state-of-the-art optical multicoatings are even more impressive when you consider the package they come in. The finely-machined scope has a dual-speed 2.5” rack-and-pinion focuser with a microfine 10:1 fine-focusing ratio. A built-in camera angle adjuster lets you fine-tune the composition of your astrophotos and the orientation of the standard equipment 2" 99% reflectivity dielectric multicoated star diagonal. The supplied 2” and 1.25” eyepiece holders use non-marring compression rings that won’t scratch your eyepiece barrels. It even comes with a finder shoe, tube rings, and a dovetail plate.

    This feature-laden 80mm Astro-Tech AT80EDT  ED triplet apochromatic refractor offers exceptional optical and mechanical performance and features at a very reasonable price. It will do just about anything you want to do with a truly portable scope. Let it into your telescope family and you may never want to let it go.

Features of this Telescope . . .

    ED apochromatic triplet refractor optics: 80mm (3.15”) aperture, 480mm focal length, f/6 focal ratio. It uses an ED (Extra-low Dispersion glass) center element to reduce spurious color halos and fringing to vanishingly low levels. All three lens elements are slow-polished for smooth surfaces, with less scattered light.

    Fully multicoated optics: The triplet objective lens has the latest state-of-the-art antireflection multicoatings on all air-to-glass surfaces for high light transmission and excellent contrast. This can easily be seen by looking into the objective lens of the scope. Virtually no reflection of your face will be seen. It’s a sure sign that the high transmission coatings are doing their job, by letting virtually all the light enter the scope, rather than reflecting some light back to your eye.

    Internal light baffles: Contrast-enhancing knife-edge light baffles in the 90mm diameter optical tube provide truly dark sky backgrounds and high terrestrial contrast. The edges of the lenses are blackened to reduce internal reflections and further improve image contrast.

    Dew shield: A self-storing retractable dew shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. It also improves the contrast, similar to the effect of the lens shade on a camera lens, when observing during the day or when there is excessive ambient light at night, such as from a neighbor’s backyard security light. 

    Dual speed 2.5” rack-and-pinion focuser: The precision-made focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with a 10:1 reduction gear microfine focusing ratio. This provides exceptionally precise image control during high magnification visual observing and critical CCD imaging. 

    The focus knobs have ribbed gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather. The focuser drawtube has 75mm of travel and a millimeter scale on the drawtube to let you return to an approximate focus when switching between visual and photographic setups. A lock knob under the focuser lets you lock in your photographic focus.  
    
    Compression ring eyepiece holders: The focuser’s 2.5” drawtube terminates in a 2” eyepiece holder that uses a non-marring compression ring to hold the standard equipment 2” star diagonal and/or accessories in place. The compression ring won’t scratch the barrel of your star diagonal and accessories as an ordinary thumbscrew can. 

    A supplied 1.25” accessory adapter slips into the 2” eyepiece holder to let you use a 1.25” star diagonal, image erecting diagonal, or photographic accessories. Like the 2” eyepiece holder, the 1.25” adapter also uses a non-marring compression ring to hold 1.25” star diagonals and accessories in place.

    Built-in camera angle adjuster: The focuser drawtube’s 2" eyepiece/accessory holder includes a built-in camera angle adjuster that lets you quickly adjust the angle of your camera for the best composition or to put the star diagonal at the most comfortable observing angle.  A knob on the 2" eyepiece/accessory holder lets you unlock the camera angle adjuster, rotate it to the desired final angle, then lock it in place at whatever angle is most convenient for you. This camera angle adjuster is standard equipment, not an optional extra-cost accessory, as it is with some other scopes.  

    Star diagonal: An Astro-Tech 1/10th wave 2” star diagonal with durable 99% reflectivity dielectric multicoatings is standard equipment. 

    Optical tube: The very compact 15" long optical tube and focuser (17" long with lens shade extended) are finished in a durable white and black powder coated finish, with black anodized trim. There is a finderscope mounting shoe that accepts Vixen-style finderscope mounting brackets. The shoe can be mounted on either the top left or top right side of the focuser body. A slip-on metal dust cap is standard, as is a dust seal for the eyepiece holder.

    Tube rings and dovetail: Dual split hinged tube rings are supplied for the 90mm o. d. optical tube. The rings are lined with white felt that will not stain the white finish of the scope over time, unlike the black felt supplied with other scopes. A 5.4" long Vixen-style dovetail is bolted to the tube rings. Optional Losmandy-style D-plate dovetails are available if your mount uses a wider Losmandy-style saddle. 


Highest Useful Magnification:
This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.
160x
Visual Limiting Magnitude:
This is the magnitude (or brightness) of the faintest star that can be seen with a telescope. The larger the number, the fainter the star that can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This is the formula that we use with all of the telescopes we carry, so that our published specs will be consistent from aperture to aperture, from manufacturer to manufacturer. Some telescope makers may use other unspecified methods to determine the limiting magnitude, so their published figures may differ from ours.

Keep in mind that this formula does not take into account light loss within the scope, seeing conditions, the observer’s age (visual performance decreases as we get older), the telescope’s age (the reflectivity of telescope mirrors decreases as they get older), etc. The limiting magnitudes specified by manufacturers for their telescopes assume very dark skies, trained observers, and excellent atmospheric transparency – and are therefore rarely obtainable under average observing conditions. The photographic limiting magnitude is always greater than the visual (typically by two magnitudes).

12
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

480mm
Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

f/6
Resolution:
This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

1.45 arc seconds
Aperture:
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
80mm
Weight:
The weight of this product.
5.5 lbs.
Telescope Type:
The optical design of a telescope.  Telescope type is classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, or by the task they perform.
Refractor
 
Based on Astronomy magazine’s telescope "report cards", scopes of this size and type generally perform as follows . . .
Terrestrial Observation:
Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes. 
Yes
Lunar Observation:
Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.  
Very Good
Planetary Observation:
Very Good
Binary and Star Cluster Observation:
Good
Galaxy and Nebula Observation:
Fair
Photography:
Yes
Terrestrial Photography:
Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.
Yes
Lunar Photography:
Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus. 
Yes
Planetary Photography:
Yes
Star Cluster / Nebula / Galaxy Photography:
Yes
Warranty:
1 year
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Photographic Accessories
Dust Covers (1)
Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes
by Astrozap
Quantity:  
$30.00 
Tele-Compressors (Photo/Visual) (1)
0.8x reducer/field flattener for Astro-Tech AT80EDT triplet apo refractor
by Astro-Tech
Quantity:  
$149.95 
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Astro-Tech AT80EDT f/6 ED Triplet Refractor OTA

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For the backyard grab-and-go observer, for the Milky Way star field scanner, for the wide field imager, for the birder and terrestrial photographer . . . the Astro-Tech AT80EDT 80mm f/6 ED triplet apo is the Swiss Army knife of refractors.





. . . our 37th year