Astro-Tech AT66EDQ f/7 ED Quadruplet Apochromatic Refractor OTA
If the AT86EDQ is the workhorse of the Astro-Tech quad family, the new AT66EDQ is the thoroughbred pony—compact, elegant, and fast on its feet. Designed as a true flat-field imaging scope with a full-frame 43.2mm image circle, the AT66EDQ offers the same precision optics and premium build quality in a more travel-friendly size and weight. At just 7.9 pounds (3.6 kg) with rings and handle, this is a refractor you’ll actually want to take into the field.
Despite its modest 66mm aperture, the AT66EDQ is no lightweight when it comes to performance. A four-element, two-group air-spaced optical design—featuring two ED glass elements (one is FK-61 and the other is a trade secret...)—delivers razor-sharp, color-free images across the entire field, without the need for an external field flattener. Whether you're imaging galaxies under dark skies or grabbing wide-field shots of the Milky Way from your backyard, the AT66EDQ gives you professional-level results in a remarkably portable package.
A True Flat-Field Astrograph—No Add-Ons Required
Like its larger siblings in the EDQ series, the AT66EDQ is designed to give you astrophotography-grade performance right out of the box. It uses an apochromatic triplet objective lens with an FK-61 ED center element to suppress chromatic aberration, and a permanently integrated rear field flattener, also made with ED glass, to eliminate field curvature. This built-in flattener corrects the image across a 43.2mm image circle—ideal for full-frame cameras and cooled astro imaging setups alike.
With this optical design, you get pinpoint stars from center to edge, perfect for wide-field mosaics, large emission nebulae, and dense Milky Way star fields. There’s no need for a separate flattener or guesswork about backfocus spacing—the field is flat, sharp, and ready to go.
Optional 0.8× Reducer – Expand Your Field, Speed Up Your Exposure
While the AT66EDQ performs beautifully at its native 462mm focal length (f/7), wide-field imagers will appreciate the optional 0.8× reducer (sold separately). This dedicated accessory threads directly into the focuser’s rear and reduces the focal length to approximately 370mm at f/5.6, giving you:
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A wider field of view for large nebulae and star complexes
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Faster exposure times for broadband and narrowband imaging
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Cleaner image scale for larger pixels or smaller sensors
The reducer maintains full-frame correction and preserves the EDQ’s hallmark edge-to-edge sharpness. It’s the perfect way to double your framing flexibility without switching scopes.
Astrograph Performance in a Travel-Ready Format
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Aperture: 66mm
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Focal Length: 462mm
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Focal Ratio: f/7
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Image Circle: 43.2mm (Full Frame)
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Design: Quadruplet Apochromatic Refractor, Air-Spaced, Two ED Elements
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OTA Length: 13.5" (343mm) with dew shield retracted; 16.5" (420mm) extended
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Weight: 7.9 lbs (3.6 kg) including rings and handle
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Backfocus Compatibility: Optimized for DSLR and dedicated astro cameras
This is an ideal telescope for photographers on the move, those with smaller equatorial mounts, or anyone looking for a wide-field complement to a longer focal length imaging setup. It’s also an excellent choice for grab-and-go visual astronomy with crisp, high-contrast performance across the board.
High-Precision 2.8" Dual-Speed Rack-and-Pinion Focuser
A premium optical system deserves a premium focuser, and the AT66EDQ delivers. The large 2.8" rack-and-pinion focuser provides both strength and precision. A dual-speed 10:1 fine-focus knob gives you the delicate control needed for perfect star shapes at high resolution. The drawtube is marked in 1mm increments and terminates in a built-in 360° camera angle adjuster, so you can easily frame your shot without adding extra accessories.
Threading options include:
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2" compression ring adapter (non-marring brass ring)
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M63, M54, and M48 male threads built in
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Fully compatible with ZWO EAF and similar electronic focusers
The robust mechanical construction ensures zero image shift or flex, even with heavier cameras and filter wheels.
Thoughtful Features for Imaging and Visual Use
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Retractable Dew Shield: Helps block stray light and slow dew formation. Retracts for transport or compact storage.
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Split Mounting Rings with Handle: Machined, felt-lined rings include a Vixen-style dovetail plate underneath and a top handle with a mini Vixen-style saddle for piggybacking guide scopes or other accessories.
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Finder/Guide Scope Shoe: A standard Synta-style mounting shoe is pre-installed for quick addition of a guide scope or finder.
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Threaded Extension Options: M48, M54, and M63 threads for connecting to your imaging train or diagonal without adapters.
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Matte Anodized Finish: Durable matte black finish with red highlights. Looks as sharp as it performs.
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Dust Cap: Machined metal, slip-on style, to protect the front lens when not in use.
Who Is the AT66EDQ Made For?
The AT66EDQ may be compact, but its usefulness spans a wide range of astronomers and imaging setups. Here’s who it’s made for:
• The Astrophotographer Looking for Flat-Field Simplicity
No more fiddling with backfocus or buying add-on flatteners. The AT66EDQ’s built-in field flattener is ready to go for full-frame or APS-C imaging right out of the box.
• The Wide-Field Imager
Its native f/7 focal length is perfect for large targets. Add the optional 0.8× reducer and you get a ~370mm f/5.6 system—excellent for sweeping nebulae, star fields, and multi-target frames.
• The Lightweight Mount Owner
If you're using a harmonic mount like the AM5 or HEM27, or a portable EQ like the Sky-Watcher Star Adventurer GTi, this scope stays well within your payload limits while still delivering serious optical performance.
• The Visual Observer Who Cares About Color Correction
The optics may be built for imaging, but the views through a good diagonal and a wide-field eyepiece are stunning—sharp, contrasty, and color-free. This isn’t a scope that makes excuses for its aperture.
• The Experienced Astronomer Looking for a Travel Scope or Second Rig
If your main scope is a heavy triplet or reflector, the AT66EDQ is an ideal wide-field companion. You can image with it while observing through something larger—or take it solo when conditions favor portability over power.
Observing Tip:
Pair the AT66EDQ with a full-frame sensor and a multi-narrowband filter to create ultra-widefield mosaics with pinpoint stars and rich nebulosity. Or use the optional 0.8× reducer and a one-shot color camera to frame entire nebula complexes in a single exposure window.
Final Thoughts:
The Astro-Tech AT66EDQ is proof that great things come in compact optical tubes. It’s a serious imaging tool with professional-grade optics, a rock-solid focuser, and a travel-friendly build. Whether it’s your first astrophotography telescope or the lightweight sidekick to a larger scope, the AT66EDQ delivers all the performance without the weight—and with the optional reducer, even more flexibility to chase the wide sky.
