The Astro-Tech AT72EDII takes the performance, and mechanics, of the "product everyone should own" (thank you Astronomy Magazine) and gives it an upgrade.
This Astro-Tech ED refractor has:
• 72mm f/6 fully multicoated FPL-53 and Lanthanum doublet refractor optics
• dual-speed Rack and Pinion 2” focuser with 10:1 ratio fine focusing and built in Camera Angle Adjuster (Same mechanism as our EDT series)
• 2” and 1.25” non-marring compression ring accessory holders
• Vixen dovetail plate with two tube rings
• retractable self-storing lens shade
• amazing wide field astrophotographic capabilities
• long-lasting white finish with powder-coated black focuser and red anodized trim
Astronomy magazine called this scope’s predecessor, the 66mm Astro-Tech AT66ED, “a product everyone should own.” The original AT72ED has proven to be a worthy upgrade over the AT66ED. Now we come to the next upgrade over the original AT72ED. The new Astro-Tech AT72EDII.
The major upgrades over the AT66ED and AT72ED come in the type of ED element and the type of focuser. The new AT72EDII has upgraded the ED element to FPL-53 with a Lathanum mating element. Our first star test on the prototype was simply textbook. A perfectly defined set of white diffraction rings with jet black spacing. The next upgrade comes with the 2" Rack and Pinion focuser with 10:1 fine focus knob. It is the same mechanism as our EDT line and is buttery smooth. The focuser also comes with a built in Camera Angle Adjuster to help you get just the right position for your camera or diagonal. The final upgrade is something that people have asked us about for years. The AT72EDII now comes with split tube rings and a Vixen style dovetail, with a 1/4-20 thread adapter on the bottom, as standard equipment. Astronomy said the AT66ED was “a great grab-and-go scope, a fine little astrograph, a super-finder scope, and a daytime spotting scope.” The same is equally true for the new AT72EDII.
This 12” long refractor optical tube (15” long with the lens shade extended) has the right balance of aperture and focal length to use as a low-power rich field telescope, as a medium-power planetary telescope, or as any kind of telescope in between. In addition, optional camera adapters turn the AT72EDII into a superb 430mm (8.6x) f/6 daytime telephoto lens and nighttime wide-field astrograph. The supplied Vixen style dovetail fits directly into the dovetail slot, or will attache to any mount or tripod with a 1/4-20 thread screw, on the top of many altazimuth and German equatorial mounts, such as those from Astro-Tech, Celestron, Meade, and Vixen. The OTA weighs in at 4.15 pounds and 4.8 pounds with rings and dovetail.
Features of this Telescope . . .
AT72EDII doublet refractor optics: 72mm (2.83”) aperture, 430mm focal length, f/6 focal ratio air-spaced doublet lens using premium ED glass, including an FPL-53 ED (Extra-low Dispersion glass) with a Lanthanum mating element to reduce spurious color halos and fringing to vanishingly low levels. While we do not claim fully apochromatic performance in the class of a multiple thousand dollar Takahashi, Astro-Physics, or TMB refractor, the AT72ED is so free from spurious color as to be virtually indistinguishable from an apochromatic system. And, as Mr. Spock probably said in one episode of Star Trek or another, “Any difference that makes no difference, is no difference.”
Multicoated optics: The objective lens has the latest state-of-the-art broadband antireflection multicoatings on all four 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: There are two contrast-enhancing knife edge baffles inside the optical tube, and 15 Micro Baffles running the full length of the focuser drawtube, for truly dark sky backgrounds and high terrestrial contrast. In addition, the edges of the objective lens are blackened to eliminate contrast-reducing stray internal reflections.
Full power range capability: The “highest useful magnification” listed above right is 143x. This is the power obtained with a 3mm eyepiece, which provides an exit pupil of 0.5mm (about 1/50th of an inch) and 51x per inch of aperture. This is generally the smallest exit pupil recommended with any telescope before the images start to become too dim to be consistently useful.
Higher powers are possible for lunar and planetary observing, however, given excellent seeing conditions, although the increasing dimness of the image will start to limit the performance on all but the brightest objects.
The lowest useful power is 11x, achieved with a 40mm eyepiece (a 40mm 1.25” TeleVue Plössl will give you a 4.2° field at that power). At 3.8x per inch of aperture, this is very close to the 4x per inch of aperture generally regarded as the lowest practical power with any telescope. A 40mm eyepiece on the AT72EDII will give you a 6.67mm exit pupil, larger than most eyes can dilate. Any lower power would simply waste some of the scope’s light gathering capacity, as its collected light would fall on your iris, rather than entering your eye.
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 a neighbor’s backyard security light.
Dual speed microfine 2” Rack and Pinion focuser with 1.25” adapter and a built in Camera Angle Adjuster: The precision-made 2” focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with 10:1 ratio reduction gear microfine focusing. This provides exceptionally precise image control during high power visual observing or critical DSLR or CCD imaging. The focus knobs have knurled gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather. The 86mm (3.38”) travel focuser drawtube has a scale marked in 1mm increments so you can note individual focuser positions for easy return to the correct focus when switching between visual use and photography. A lock knob under the focuser lets you lock in your photographic focus.
The focuser drawtube terminates in a 2” compression ring accessory holder to accept a 2” star diagonal and 2” photo accessories.
The supplied 1.25” accessory adapter slips onto the 2” accessory holder and uses a soft brass compression ring to hold 1.25” star diagonals and photo/visual accessories in place. The 1.25” and 2” compression rings won’t scratch the barrels of your star diagonal or accessories as an ordinary thumbscrew can.
Tube finish: The optical tube is finished in a white powder coat with red trim and a black powder-coated focuser.
The AT72EDII includes a nylon soft carry bag to help protect your scope on its travels to and from your observing field.
Other supplied accessories: A slip-on metal dust cap is standard. Two threaded holes for installing a finderscope mounting bracket are located on the upper left and upper right side of the scope body.
