The AT150EDL is an outstanding visual refractor and an excellent imaging telescope—but like every refractor, it was designed around a curved focal plane. A camera sensor is flat. The AT150EDLRF bridges that gap while reducing the focal length from 1200mm to 960mm and increasing the imaging speed to f/6.4. The result is wider fields, shorter exposures, and pinpoint stars from corner to corner.
Designed for One Scope
This is not a universal reducer. Its element spacing and correction are computed for the specific field curvature of the Astro-Tech AT150EDL 150mm f/8 FCD-100 doublet. A generic 0.8x reducer can shorten focal length, but it can't correct the curvature your scope actually produces — you end up trading corner coma for a different corner aberration. This one is matched to the AT150EDL. It may thread into another f/8 refractor that shares the M92 focuser connection, but flat, corrected stars are only guaranteed on the scope it was built for.
How It Connects
The scope side threads directly into the M92 drawtube of the AT150EDL's 3.2" rack-and-pinion focuser — M92×1 metric threads, a secure, repeatable connection with no compression ring and no wobble. There are no intermediate adapters and no back-focus arithmetic to second-guess: thread it in, set your spacing, and the 1200mm f/8 doublet becomes a 960mm f/6.4 wide-field astrograph.
The camera side gives you two direct threading options — M48×0.75 or M54×0.75 male — so you can match whichever your gear uses without a stack of step rings. Dedicated CMOS and CCD astronomy cameras connect directly via whichever thread matches their back plate; most have an M54 or M48 back plate built in, so no T-ring is needed. DSLR and mirrorless cameras connect via a T-ring for your specific mount (sold separately), threading to the M48 side.
Back focus is 55mm from the shoulder of the reducer to the image plane — standard spacing that most T-ring-and-camera and dedicated-camera back plates reach naturally. Getting this distance right is what holds the correction together in the corners, so confirm your camera's sensor-to-flange distance and add spacers if needed to land on 55mm.
What's Included
- Astro-Tech AT150EDLRF 0.8x reducer/field flattener
- Thread-on dust cap, scope side
- Thread-on dust cap, camera side
Features
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0.8x focal reduction — Converts the AT150EDL from 1200mm f/8 to 960mm f/6.4. That's a 56% increase in photographic speed: the same target reaches the same signal in roughly two-thirds the exposure time. Meaningful on any night when clouds or sleep are coming.
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Integrated field flattener — The AT150EDL is a doublet, with the gentle field curvature that comes with the design. The AT150EDLRF corrects that curvature so stars stay round and sharp into the corners of your chip — no separate flattener, no guesswork about which one pairs with the scope.
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M92 scope-side connection — Threads straight into the 3.2" focuser drawtube. No adapters, no shimming, no shift between sessions.
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Dual camera-side threads (M48 / M54) — Two direct threading options cover most imaging trains without extra hardware. Dedicated CMOS and CCD cameras attach directly; DSLR and mirrorless bodies connect via a T-ring (sold separately) to the M48 side.
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Fully multi-coated optics — Broadband anti-reflection coatings on every surface preserve contrast and control internal ghosting across the full wavelength range — the kind of stray-light control that matters when a bright star sits in the frame.
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55mm back focus — Standard spacing from reducer shoulder to sensor, compatible with most camera-and-adapter combinations without custom spacers.
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Includes thread-on dust caps — One for each end, to protect the coated surfaces between sessions.
What You'll Frame
At 960mm and f/6.4, the AT150EDL keeps the reach a 6-inch is prized for while opening the field enough to work comfortably. On a full-frame sensor you frame the brighter galaxies with room around them — M81 and M82 together, the M101 pinwheel, the edge-on stretch of NGC 4565. The Eastern Veil fits cleanly, the Dumbbell (M27) sits well-proportioned rather than cramped, and globulars like M13 and M5 resolve with sharp, round stars to the edge. It's a focal length that suits an imager who wants galaxies and medium-sized nebulae sharp, not a stamp-collection of the whole sky in one shot — and with the reduction in place, you collect that data faster than the native f/8 ever would.
Imaging Tip
When you first set up the AT150EDLRF, shoot a 30-second test frame of a moderately rich star field and inspect the corners at 100%. If the corner stars are stretched radially — pointing away from center, like little arrows toward the edge — your sensor is too far from the reducer; pull a spacer. If they're stretched tangentially — smeared sideways — you're too close; add a thin spacer. The 55mm spec is measured from the shoulder of the reducer, not the rear element, so make sure your stack is referenced from the right point before you chase the number with shims.
Frequently Asked Questions
Will this reducer work with my AT102EDL or AT125EDL?
No. Each EDL scope has its own dedicated reducer matched to its specific focal length and field curvature. The AT102EDL uses the AT102EDLRF, the AT125EDL uses the AT125EDLRF, and the AT150EDL uses the AT150EDLRF. They are not interchangeable — using the wrong one gives you incorrect correction and unpredictable corners.
Do I need a T-ring to connect my camera?
It depends on your camera. Dedicated CMOS and CCD astronomy cameras (ZWO, QHY, Player One, and similar) typically have an M54 or M48 back plate built in and thread directly onto the matching side of the AT150EDLRF — no T-ring needed. DSLR and mirrorless cameras (Canon, Nikon, Sony, Fuji) connect via a T-ring for your specific lens mount, threading to the M48 side. The T-ring is sold separately.
Should I use the M48 or the M54 thread?
Use whichever matches your camera's back plate or adapter. M54 carries a wider unobstructed aperture and is the common choice for full-frame dedicated cameras and 2" filter trains; M48 is the standard for T-ring connections and APS-C setups. Both reach the same 55mm back focus — pick the one that lets you build the cleanest, most secure stack.
What is the correct back focus distance?
55mm from the shoulder of the reducer to your camera's sensor. Most dedicated-camera back plates and T-ring combinations land close to this naturally, but confirm your specific camera's flange-to-sensor distance before ordering spacers. Getting it right is what keeps the corners corrected on a full-frame chip.
Can I use this reducer visually?
No. The AT150EDLRF is designed for prime-focus astrophotography. It will not reach focus with an eyepiece and is not intended for visual use — for visual observing, use the AT150EDL as-is.
Can I add a filter?
Yes — you can place a threaded 2" (48mm) filter in the camera-side train between the reducer and the sensor. Remember that a filter shifts the optical back focus by roughly one-third of its glass thickness, so account for it when you set your spacing to 55mm.
Final Thoughts
If you're imaging through the AT150EDL, this is the reducer it was designed around. It flattens the doublet's field, speeds the system from f/8 to f/6.4 so your subs do more in less time, and threads in through a solid M92 connection that doesn't shift between sessions. The dual M48/M54 camera side fits the way modern imaging trains are actually built. The AT150EDL already earns its reputation at the eyepiece. The AT150EDLRF lets it earn the same reputation behind the camera. Wider fields, flatter stars, shorter exposures—the telescope you already enjoy becomes an even more capable imaging instrument without changing its character.
