Astro-Tech AT126EDQ f/7 Quad Refractor

Most refractors need a separate field flattener to image properly. You buy the scope, then you buy the flattener, then you figure out the spacing, then you hope the correction matches the optical system well enough to deliver round stars in the corners. It works — we sell a lot of flatteners — but it's an extra piece of glass, an extra connection, and one more thing to get right.

The AT126EDQ takes a different approach. The field correction is built in. The four-element, two-group optical system uses an ED element in the apochromatic triplet objective and a second ED element in a separate internal field-flattening group. The result is a flat, corrected field straight from the focuser — no external flattener required. Stars are round from center to edge across sensors up to full frame, with a 44mm corrected image circle. You bolt the camera to the focuser and shoot.

At 126mm of aperture and 882mm f/7, this is the largest scope in the EDQ line. More aperture means more light, more resolution, and more reach into faint structure. The AT86EDQ and AT106EDQ are excellent instruments for their size, but 126mm puts you into a different class of target — fainter galaxies, tighter nebula detail, smaller planetary nebulae that need the extra resolution to show their structure. And you get all of that with the flat field that defines the EDQ design.

The Quad Optical Design

The AT126EDQ is a four-lens, two-group system. The front group is an apochromatic triplet with one ED element — this handles the heavy lifting of color correction and primary image formation. Behind it, a separate group containing a second ED element flattens the field. The two groups work together as a system: the triplet delivers a sharp, color-free image, and the flattener ensures that image lands flat across a sensor up to 36×24mm.

All lens surfaces are fully multicoated with antireflection coatings matched to their specific glass types. The result is high light transmission, excellent contrast, and clean images free of the faint color halos that plague lesser optical designs. At f/7, the AT126EDQ controls chromatic aberration exceptionally well — bright stars show no color fringing, and high-contrast targets like the lunar limb and planetary discs are clean.

Built-In Flat Field — No Flattener Required

This is the defining advantage of the EDQ design. With a conventional triplet or doublet refractor, the focal plane curves. Stars in the center are sharp, but stars at the edges elongate as the curved focal surface diverges from the flat sensor. An external field flattener corrects this — but you have to buy it separately, get the back focus spacing right, and hope the correction is well-matched to the scope.

The AT126EDQ eliminates all of that. The internal ED field-flattening group is optically matched to the objective lens because it was designed as part of the same system. The 44mm corrected image circle covers full-frame sensors with flat, round stars from center to corners. No external flattener to buy, no spacing to calculate, no wondering whether a generic flattener will work with your specific scope. It's done.

If you want to go faster, we sell a dedicated 0.8× reducer that drops the AT126EDQ from 882mm f/7 to 706mm f/5.6 — a 56% increase in light per pixel, shorter exposures, and a wider field. Because the field is already flat, the reducer's only job is focal reduction. It preserves the flat field the scope was designed to deliver.

Under the Night Sky

126mm of aperture in a refractor is serious glass. The resolution limit is 1.1 arc seconds — enough to split tight doubles and resolve fine planetary detail that smaller scopes can't touch.

Moon: At 126mm, the Moon is deeply detailed. The Alpine Valley rille is visible under good seeing. Craterlets on the floor of Plato resolve as individual pits rather than a general roughness. The terraced walls of Copernicus show their full complexity, and the Straight Wall casts a razor-sharp shadow at the right phase. At 200× to 248×, you're seeing structure that disappears in an 80mm or 90mm scope.

Planets: Jupiter shows the major equatorial belts with internal festoon structure, the Great Red Spot with visible texture, and shadow transits as sharp black dots. Saturn's Cassini Division is a clean, dark line at moderate power, and the crepe ring is visible against the planet's disc with careful observation. Mars at opposition shows dark surface markings — Syrtis Major, the polar cap, and limb clouds — with the color fidelity that only a well-corrected refractor delivers.

Double stars: With a 1.1 arc second Dawes limit, the AT126EDQ splits doubles that challenge smaller scopes. Epsilon Lyrae (the Double Double) is cleanly resolved at 150×. Zeta Herculis at 1.4" splits with dark space between the components. Porrima (Gamma Virginis) and Castor are textbook pairs. The clean, high-contrast Airy discs that a good refractor produces make doubles one of its strongest visual subjects.

Deep sky: 126mm gathers enough light to show real structure in the brighter Messier objects. M13 begins to resolve individual stars across its face at 150×. M42 shows the Trapezium as four clean stars with nebulosity streaming away from them. M57 (the Ring Nebula) shows its annular shape clearly with a hint of the central star under excellent conditions. The Veil Nebula complex responds well to an O-III filter. Galaxy hunters will see the dust lane in M82, the spiral hints in M51 with averted vision, and the bright cores of dozens of galaxies in Virgo and Coma — and the flat field means stars at the edge of your eyepiece field are as sharp as those in the center.

For the Imager

The AT126EDQ was designed with imaging in mind. At 882mm f/7 with a flat field to full frame, it frames mid-size deep-sky targets with excellent image scale and sharp stars from center to corners without any additional corrective optics. The Rosette Nebula, the Crab Nebula, galaxy groups like the Leo Triplet, the Veil complex — these targets fill an APS-C frame beautifully at 882mm, and full-frame shooters get even more field to work with.

Add the optional ATEDQR 0.8× reducer and the system drops to 706mm f/5.6. The wider field opens up larger targets — the North America Nebula, M31 with companions, the Heart and Soul pair — and the faster focal ratio cuts exposure times. The 56% increase in light per pixel means you can either shoot shorter subs or reach fainter structure in the same integration time.

The camera angle adjuster is standard equipment — rotate the camera to frame your target in landscape, portrait, or any angle in between without disassembling the imaging train. The focuser drawtube has a millimeter scale for noting focus positions, and the focus lock prevents shift during long exposures. The focuser is also compatible with electronic focusers like the ZWO EAF for remote focusing during imaging sessions.

The Focuser

The AT126EDQ's 3.2" rack-and-pinion focuser is built for imaging loads. The right focus knob has a concentric 10:1 fine-focus knob for precise control — critical when you're dialing in focus on a camera sensor. The focuser drawtube terminates in a built-in camera angle adjuster that rotates a full 360° and locks at any position. This is standard equipment, not an extra-cost accessory.

The focuser provides multiple thread options: M63, M54, and M48. This gives you flexibility to connect reducers, filter wheels, and cameras without stacking adapters. The 2" accessory holder uses non-marring brass compression rings — no thumbscrew gouges on your eyepiece barrels. A 1.25" adapter is included for smaller eyepieces and accessories.

The drawtube has a scale marked in 1mm increments so you can record focus positions for different accessories. A lock knob under the focuser secures focus during imaging runs. The combination of smooth coarse motion, precise fine focusing, and a solid lock makes this focuser practical for both visual and photographic use without compromise.

Build and Mechanical

The AT126EDQ is finished in matte black anodize with black-anodized focuser and red accent appointments. The retractable dew shield slides forward from 28.6" retracted to 34.7" extended — functional for dew prevention and stray light control, and self-storing so there's nothing to lose or leave at home.

The scope ships with felt-lined hinged split mounting rings with M6×1 thread mounting holes in the top and bottom of each ring. A Vixen-style dovetail and a handle with a mini Vixen saddle plate are included. For heavier equatorial mounts, the rings accept a Losmandy-style D-plate dovetail (sold separately). A dovetail shoe on the upper focuser accepts optional finders or guide scopes.

At 17.67 pounds with rings, dovetail, and handle, the AT126EDQ needs a solid mount — an HEQ5-class equatorial or a ZWO AM5 will handle it for imaging. The heaviest single component is 15.6 pounds. The scope ships in a cordura nylon carry case with cutouts for accessories.

What's Included

• AT126EDQ optical tube assembly
• Felt-lined hinged split mounting rings (pair) with M6×1 mounting holes
• Carrying handle with mini Vixen saddle plate
• Vixen-style dovetail plate
• 2" accessory holder with brass compression ring
• 1.25" accessory adapter with brass compression ring
• Retractable dew shield
• Finderscope mounting shoe
• Slip-on metal dust cap
• Cordura nylon carry case

Features

• Quadruplet optical system with two ED elements. Four-lens, two-group design: an apochromatic ED triplet objective plus a separate internal ED field-flattening group. Clean color correction and a flat field are built into the optical system — not added as an afterthought.
• Built-in flat field to full frame — no external flattener required. The internal ED field-flattening group delivers a 44mm corrected image circle. Stars are round from center to edge across full-frame (36×24mm) sensors. Skip the separate flattener and the spacing guesswork.
• 126mm aperture at 882mm f/7. The largest scope in the EDQ line. Enough aperture and focal length for detailed imaging of mid-size deep-sky targets and serious visual observing — planetary detail, double stars, and deep-sky structure.
• Fully multicoated optics. All air-to-glass surfaces carry antireflection multicoatings matched to their glass types. High light transmission, excellent contrast, and clean images free of color fringing.
• Compatible with the ATEDQR 0.8× reducer. Add the dedicated reducer (sold separately) to drop from 882mm f/7 to 706mm f/5.6 — 56% more light per pixel, shorter exposures, and a wider field — while preserving the flat field.
• 3.2" dual-speed rack-and-pinion focuser with 10:1 fine focus. Beefy, precise, and imaging-capable. Coarse and fine focusing with ribbed knobs operable in gloves. Focus lock and mm-scale drawtube markings. EAF compatible.
• Built-in camera angle adjuster. 360° rotation standard — not an extra-cost accessory. Frame targets in any orientation without disassembling the imaging train.
• M63, M54, and M48 focuser threads. Multiple thread options for connecting reducers, filter wheels, and cameras without stacking adapters.
• Non-marring brass compression rings. Both 2" and 1.25" accessory holders use soft brass compression rings that grip without scratching your eyepiece or accessory barrels.
• Retractable dew shield. Self-storing — slides forward for use, retracts for transport. Controls dew and stray light without a separate accessory to track.

Observing Tip

If you're imaging with the AT126EDQ at its native f/7 and you find yourself wanting a wider field or shorter exposures for larger targets, the ATEDQR 0.8× reducer drops you to 706mm f/5.6. But don't overlook what f/7 gives you visually while your camera is cooling down or while you're waiting for your target to clear the trees. At 882mm, a 10mm eyepiece delivers 88× in a wide field — plug in an O-III or UHC filter and sweep through Cygnus. The flat field means the stars at the edge of your eyepiece are as sharp as those in the center, which makes visual sweeping noticeably more pleasant than with a conventional refractor.

Frequently Asked Questions

Do I need a separate field flattener with this scope?
No. The AT126EDQ has a built-in ED field-flattening group that delivers a flat, corrected field across full-frame sensors. You don't need an external flattener — it's one of the primary advantages of the quad design. The only accessory optic you might add is the optional 0.8× reducer if you want a faster focal ratio and wider field.

What mount do I need?
At 17.67 lbs with rings and dovetail, the AT126EDQ needs a mount rated for at least 30 lbs for imaging — an HEQ5 or EQ6-class equatorial, or a ZWO AM5. For visual use, the mount requirements are less demanding. A solid alt-az mount or a lighter equatorial will work, but this is not a grab-and-go scope.

What's the difference between the AT86EDQ, AT106EDQ, and AT126EDQ?
Same optical design philosophy in three aperture sizes. The AT86EDQ (86mm, 602mm f/7) is the grab-and-go option — light, compact, airline-friendly. The AT106EDQ (106mm, 742mm f/7) is the mid-size sweet spot. The AT126EDQ (126mm, 882mm f/7) is the largest — most aperture, most focal length, most resolving power, but also the heaviest and most demanding on a mount. All three share the quad design with built-in flat field and are compatible with the same ATEDQR 0.8× reducer.

Can I use this visually, or is it imaging-only?
The AT126EDQ works beautifully for visual observing. The quad design was built around imaging, but 126mm of clean, well-corrected aperture delivers excellent planetary, double star, and deep-sky views. The flat field is an advantage visually too — stars are sharp to the edge of the eyepiece field, which makes sweeping star fields and open clusters particularly satisfying.

Does this come with a finder?
No — a finderscope mounting shoe is included on the focuser housing, but you'll need to add your own finder or guide scope. This lets you choose the finder that matches your setup — a red-dot finder for visual, or a guide scope for imaging.

Accessories

• ATEDQR 0.8× Reducer: Drops the AT126EDQ from 882mm f/7 to 706mm f/5.6. Faster exposures, wider field, full-frame coverage. Designed specifically for the EDQ series.
• T-ring for your camera mount: Required for connecting DSLR and mirrorless cameras to the focuser's 48mm T-threads. Dedicated CMOS/CCD astronomy cameras typically have 48mm T-threads built in and connect directly.
• Finder or guide scope: The AT126EDQ ships with a finderscope shoe but no finder. Add a red-dot finder for visual use or a guide scope for autoguided imaging.
• ZWO EAF electronic focuser: Compatible with the AT126EDQ's focuser. Provides motorized, software-controlled focusing for remote imaging sessions.

Final Thoughts

The AT126EDQ is the largest flat-field quad refractor in the Astro-Tech line — 126mm of aperture at 882mm f/7 with a built-in ED field flattener that delivers round stars across full-frame sensors without an external corrector. For imagers, that means one less piece of glass in the train, one less spacing calculation, and one less thing to go wrong. For visual observers, it means 126mm of clean, well-corrected aperture with pinpoint stars to the edge of the field. Add the 0.8× reducer and you have two imaging systems in one scope — f/7 for image scale on smaller targets, f/5.6 for speed and field on larger ones. If you want a refractor that images flat out of the box and gives up nothing visually, and you have the mount to carry it, the AT126EDQ is the scope that does both without compromise.