The AT80EDLRF is the dedicated 0.8× reducer and field flattener for the Astro-Tech AT80EDL f/7 doublet APO refractor. It does two things at once: it reduces the AT80EDL's 560mm f/7 focal length to 448mm f/5.6 — almost a full stop faster — and it flattens the field, delivering sharp, round stars from the center of the sensor to the corners. Without a flattener, every refractor produces a curved focal plane. Stars in the center are sharp, but stars toward the edges of the frame elongate as the curved image surface diverges from the flat sensor. The AT80EDLRF corrects that curvature and gives you a flat field across DSLR and dedicated astronomy camera sensors.
At f/5.6, exposures are shorter, the field of view is wider, and the system is better matched to the fast download cycles of modern CMOS cameras. If the AT80EDL is your imaging platform, this is the reducer designed for it.
Designed for the AT80EDL
The AT80EDLRF is optically matched to the AT80EDL's doublet FCD-100 objective. It threads directly into the camera angle adjuster (CAA) on the AT80EDL's focuser drawtube via M63×1 threads on the scope side. The camera side has standard 48mm T-threads (M48×0.75) — DSLR and mirrorless cameras connect via a T-ring for your specific mount (sold separately), while dedicated CMOS and CCD astronomy cameras typically have 48mm T-threads built in and connect directly without a T-ring.
While the AT80EDLRF may physically thread into other f/7 refractors that use a 2.5" focuser with M63 threads, its optical correction is designed around the AT80EDL's specific optical system. Performance with other scopes is not guaranteed.
Backfocus and Spacing
Backfocus is 55mm from the shoulder of the reducer to the image plane — the standard spacing for DSLR camera bodies with a T-ring. If you're using a dedicated astronomy camera, you may need spacers to achieve the correct 55mm distance, depending on your camera's backfocus requirement. The optical diagram provided on this page shows exact dimensions for calculating your imaging train spacing.
Built-In Filter Access
The top section of the AT80EDLRF unscrews from the body, exposing 48mm filter threads on the underside of the removed cap. This lets you thread a standard 2" (48mm) filter — narrowband, light pollution, UV/IR cut — directly into the optical path without adding a separate filter drawer or changing your backfocus distance. The filter sits between the reducer optics and the telescope, in the correct position for the converging light cone.
What's Included
- AT80EDLRF 0.8× reducer/field flattener
- Slip-on rubber dust cover (camera-side T-threads)
- Slip-on dust cover (scope-side barrel)
Features
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0.8× focal reduction — 560mm f/7 becomes 448mm f/5.6. Almost a full stop faster. Shorter exposures, wider field, and better matched to fast-readout CMOS cameras.
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Field flattener corrects the AT80EDL's native field curvature. Round, sharp stars from center to corners across DSLR and dedicated astronomy camera sensors. No edge elongation.
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Designed specifically for the AT80EDL doublet APO. Optically matched to the AT80EDL's FCD-100 objective. Threads directly into the CAA via M63×1 threads.
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Fully multicoated optics. All air-to-glass surfaces carry broadband multicoatings for high light transmission and minimal scatter.
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48mm T-threads on the camera side. DSLR and mirrorless bodies connect via a T-ring (sold separately); dedicated CMOS/CCD astronomy cameras attach directly — 48mm T-threads are standard on most.
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55mm backfocus — standard DSLR spacing. A T-ring and DSLR body typically land right at the correct distance. Astronomy cameras may need spacers.
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Built-in 48mm filter access. Unscrew the top cap to thread a 2" filter directly into the optical path. No separate filter drawer needed.
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Compact and lightweight. 67mm diameter, 71.51mm long, 8 oz. Adds minimal weight and length to the imaging train.
Frequently Asked Questions
Do I need this reducer, or can I use a generic field flattener?
The AT80EDLRF is designed to match the AT80EDL's specific optical curve. A generic flattener may not correct the field as well, and a generic reducer will almost certainly introduce coma or other aberrations that the matched reducer avoids. For best results with the AT80EDL, this is the one to use.
Can I use this as a 1× flattener without the reduction?
No. The AT80EDLRF is a combined reducer/flattener — it always reduces to 0.8×. If you want flat-field correction at the native 560mm f/7 focal length, you would need a dedicated 1× field flattener (not currently offered for the AT80EDL in the Astro-Tech line).
Will this work on my AT102EDL or AT125EDL?
Each EDL scope has its own dedicated reducer/flattener. The product manual PDF is shared across the AT80EDL, AT102EDL, and AT125EDL models, but the reducers themselves are separate SKUs matched to each scope's optics. Use the reducer designated for your specific scope.
How do I connect my camera?
DSLR and mirrorless cameras connect via a T-ring for your specific mount (sold separately). Dedicated CMOS and CCD astronomy cameras typically have 48mm T-threads built in and connect directly without a T-ring. The 55mm backfocus is measured from the reducer's shoulder to the sensor plane.
Can I use filters with this reducer?
Yes. Unscrew the top cap of the reducer to access the built-in 48mm filter threads. Standard 2" (48mm) threaded filters — narrowband, LP, UV/IR cut — thread in directly. This keeps the filter in the correct optical path position without adding a separate filter drawer.
Accessories
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T-ring for your camera mount (sold separately): Required for connecting DSLR and mirrorless cameras. Available for Canon EOS, Nikon F, Sony E, and other mounts. Dedicated CMOS/CCD astronomy cameras connect directly via 48mm T-threads.
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48mm (2") filters: Narrowband, light pollution, UV/IR cut filters thread directly into the reducer's built-in filter holder.
Final Thoughts
The AT80EDLRF does what a matched reducer/flattener should do: it makes the AT80EDL a faster, wider-field imaging system with a flat, corrected field — and it does it in a compact, 8-ounce package that threads directly into the focuser's camera angle adjuster. If you're imaging with the AT80EDL, this is the reducer designed for your scope. The 48mm T-threads connect to your camera, the built-in filter access keeps your optical train simple, and the 55mm backfocus is standard DSLR spacing. One piece, one connection, no guesswork on optical matching.
