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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