Astro-Tech AT72ED 72mm f/6 ED doublet refractor
called this scope’s predecessor, the 66mm Astro-Tech AT66ED, “a product
everyone should own." The new Astro-Tech AT72ED upgrades that
best-selling predecessor by increasing the aperture to 72mm to give you
9% higher resolution and 19% more light gathering; upgrades the focuser
to 2", with a 1.25" adapter; and increases the focuser travel to 80mm to
allow imaging with a wider variety of camera types. 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 AT72ED.
The images from the 430mm f/6 ED air-spaced doublet optics of this
Astro-Tech AT72ED refractor are virtually free from spurious color
(chromatic aberration), even at high magnifications. At its low price,
the optical performance is little short of astonishing. The exceptional
AT72ED optics are even more impressive when you consider the package
they come in. The finely-machined scope has a dual speed 2"
Crayford-style focuser with a microfine 10:1 fine-focusing ratio. You
can rotate the focuser a full 360° to put your eyepiece or camera in the
most comfortable observing position. The supplied 2" and 1.25" eyepiece
adapters use non-marring brass compression rings that won’t scratch your
eyepiece and accessory barrels. The Astro-Tech AT72ED has a retractable
lens shade and comes in a locking aluminum-frame hard carrying case.
This 12" long refractor optical tube (14.5" 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. Its compact size, light weight,
and convenient removable L-shaped mounting foot that mounts on any
photographic tripod also make it an excellent terrestrial spotting scope
for vacations, birding, or nature studies. In addition, optional camera
adapters turn the AT72ED into a superb 430mm (8.6x) f/6 daytime
telephoto lens and nighttime wide-field astrograph. The tripod mounting
foot is also a dovetail adapter that fits directly into the dovetail
slot on the top of many altazimuth and German equatorial mounts, such as
those from Astro-Tech, Celestron, Meade, and Vixen.
Features of this Telescope . . .
ED doublet refractor optics: 72mm (2.83") aperture, 430mm focal length,
f/6 focal ratio air-spaced doublet lens using premium Ohara glass from
Japan, including an ED (Extra-low Dispersion glass) 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
Internal light baffles: There are three contrast-enhancing knife edge
baffles inside the optical tube, and anti-reflection threading 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
· 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; while a
2" Astro-Tech 40mm Titan Type II ED
will give you a 6.33° field). 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 AT72ED 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
Dual speed microfine 2" Crayford focuser with 1.25" adapter: 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 rubber and
ribbed gripping surfaces so they are easy to operate, even while wearing
gloves or mittens in cold weather. The 80mm (3.15") 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. A lock
knob on the top of the scope allows the focuser to be rotated a full
360°. This lets you rotate the focuser to line up a camera in either a
landscape or portrait orientation (or any orientation in between), as
well as put a star diagonal and eyepiece into the most comfortable
observing position, and then temporarily lock the focuser in that
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.
Combined equatorial dovetail/tripod adapter: The AT72ED has a removable
L-shaped dovetail mounting foot/tripod adapter. The 1.75" wide x 3.25"
long mounting foot is sized and shaped (with slanted sides) to fit the
Vixen-style dovetail slot on the head of many altazimuth and equatorial
mounts. It will fit, without modification, the Astro-Tech Voyager
altazimuth mount and the Celestron CG-5 and Advanced Series, Meade
LXD-75, and Vixen Great Polaris German equatorial mounts, among others.
In addition, the mounting shoe has two 1/4"-20 thread mounting holes
that allow it to be installed on any camera tripod that has a standard
1/4"-20 thread mounting bolt. You can choose the mounting hole that
provides the best balance when used with your particular combination of
star diagonal, eyepiece, and/or camera. Cork pads on the underside of
the mounting shoe help keep the scope from swiveling when mounted on a
Tube finish: The optical tube is finished in a durable liquid black
anodize with anodized black trim.
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 side of the scope body. One hole keeps the finder in a
fixed position relative to the scope’s mounting foot, regardless of how
the focuser is rotated. The other rotates with the focuser, keeping the
finder in the same position relative to the focus knobs, again no matter
how the focuser is rotated.
Shipping/storage case: The scope comes in a 15.5" x 10" x 7.5"
aluminum-frame locking hard case with carry handle. The foam-fitted case
has cutouts for the scope, a 1.25" or 2" star diagonal, and up to three
eyepieces (two 1.25" and one 2").
Astro-Tech is one of the very few manufacturers to provide a case at
no charge for protection during shipping and as a storage convenience
when the scope is not in use. Unfortunately, FedEx, UPS, and the Postal
Service are very good at treating packages roughly. Occasionally, your
scope can arrive in perfect condition, but with the walls of the
shipping case dented in transit from rough handling, or the aluminum
frame sprung, rendering the appearance of the case less than pristine.
Damage to the shipping/storage case in such instances is not covered by
Two year warranty: As an expression of the confidence Astronomy
Technologies has in the quality of their products, the Astro-Tech AT72ED
is protected by a two-year limited warranty against flaws in materials
and workmanship (shipping case excluded).