The AT130EDT is one of the more capable imaging refractors in our lineup — 130mm of FK-61 triplet glass at 910mm f/7, sharp enough to resolve detail that smaller scopes can't touch. But at f/7, the field curves. Stars in the center are pinpoints. Stars at the edges start to elongate and blur. The scope isn't doing anything wrong — every uncorrected refractor does this. A flat sensor and a curved focal plane simply don't agree, and the longer the focal length, the more obvious the disagreement becomes.
The AT130EDTFF is a dedicated 1× field flattener that corrects this without changing anything else about the optical system. You keep the full 910mm focal length. You keep f/7. You keep the image scale you chose this scope for. What changes is the field — it goes flat. Stars are round from center to edge across full-frame sensors. The optics the AT130EDT was designed to deliver now reach every corner of your chip.
Why 1× Instead of a Reducer?
We also make a 0.8× reducer/field flattener for the AT130EDT. That drops the focal length to 728mm at f/5.6 — faster exposures, wider field, but a different image scale. The 1× flattener is for imagers who specifically chose the AT130EDT for its 910mm focal length and don't want to give it up. If you're shooting smaller targets — planetary nebulae, galaxy details, tight emission structures — the full 910mm gives you the resolution and image scale to frame them properly. The flattener makes sure the field is flat while you use it.
Connection and Installation
The scope side of the AT130EDTFF has an M63 threaded connection that threads directly onto the AT130EDT focuser drawtube — or onto the Camera Angle Adjuster if you're using the rotation feature. No barrel insert. No adapter. Just threads — secure, repeatable, and square to the optical axis every time you set up.
The camera side terminates in 48mm T-threads. DSLR and mirrorless bodies connect via a T-ring for your specific camera mount (sold separately). Dedicated CMOS and CCD astronomy cameras typically have 48mm T-threads built in and connect directly without a T-ring.
Back focus is 55mm from the flattener's shoulder to the sensor. ZWO filter wheel + OAG + camera stacks are designed for 55mm and bolt together directly. A DSLR with a standard T-ring typically hits the spacing naturally. Dedicated cameras with different flange distances may need 48mm spacer rings to dial it in.
Inline Filter Thread
The top section of the flattener body unscrews, exposing a 2" filter thread on the lower section. Thread in a light pollution, UHC, or narrowband filter without adding a separate filter drawer or filter wheel. For one-shot color camera setups with a single broadband or dual-narrowband filter, this keeps the imaging train short and the back focus math simple.
Features
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1× dedicated field flattener — no focal reduction. Maintains the AT130EDT's native 910mm f/7. Flattens the field for round stars from center to edge without changing image scale or field of view.
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Full-frame sensor coverage. Corrects field curvature across full-frame (36×24mm) sensors and smaller. Round stars in the corners, not just the center.
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Optically matched to the AT130EDT. Designed for the AT130EDT's specific focal length and field curvature. Delivers better edge correction than generic flatteners because the optical correction is tuned to this scope.
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M63 threaded scope-side connection. Threads directly to the AT130EDT focuser drawtube or Camera Angle Adjuster. No barrel insert, no adapter — secure, tilt-free positioning every session.
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48mm T-thread camera connection. 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 back focus. From the flattener shoulder to the sensor. Standard DSLR T-ring spacing typically hits this naturally. ZWO filter wheel + OAG + camera stacks are designed for 55mm.
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2" inline filter thread. Unscrew the top section to expose a 2" filter thread for inline filter use without a filter drawer.
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Fully multi-coated optics. Maximizes light transmission and minimizes internal reflections.
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Lightweight at 9.5 oz. Minimal impact on balance or focuser load.
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Protective covers included. Slip-on rubber covers for both ends.
Observing Tip
At 910mm, the AT130EDT with the 1× flattener is a natural match for smaller deep-sky targets — planetary nebulae like M57, M27, and NGC 7662 fill the frame beautifully at this focal length. Galaxy groups like the Leo Triplet or Markarian's Chain get enough image scale to show detail without being too tight to frame. If you find yourself cropping every image you take with the 0.8× reducer because the target is too small in the frame, the 1× flattener gives you the image scale you actually want — and the flat field to use it properly.
Frequently Asked Questions
What's the difference between this and the 0.8× reducer/flattener?
The AT130EDTFF is a 1× flattener — it corrects field curvature without changing focal length. You keep 910mm at f/7. The 0.8× reducer/flattener reduces to 728mm at f/5.6 — faster exposures (56% more light per pixel), wider field, but different image scale. Choose the 1× for full-resolution imaging of smaller targets. Choose the 0.8× for wider fields and shorter exposures.
Does this cover a full-frame sensor?
Yes. The corrected image circle covers full-frame 36×24mm sensors with flat, round stars from center to edge.
Do I need a T-ring?
If you're using a DSLR or mirrorless camera, yes — you need a T-ring for your specific camera mount (sold separately). Dedicated CMOS and CCD astronomy cameras typically have 48mm T-threads built in and connect directly.
Can I use a filter wheel with this?
Yes. A ZWO filter wheel + OAG + camera stack is designed to hit 55mm back focus. Thread the flattener onto the scope, attach the filter wheel to the 48mm T-threads, and the system is at the correct spacing.
How critical is the 55mm back focus?
Very. If the spacing from the flattener's shoulder to your sensor is off by more than a couple of millimeters, you'll see elongated stars toward the edges. M48 spacer rings in 1mm, 2mm, and 5mm increments let you dial it in. Measure once, mark your configuration, and it stays consistent.
Final Thoughts
The AT130EDT at 910mm f/7 has the focal length and resolution to frame smaller targets with real detail. The AT130EDTFF makes sure that resolution reaches every corner of your sensor. It threads on, stays square, flattens the field across full frame, and doesn't change your image scale. If you're imaging with the AT130EDT and you want flat fields at the full 910mm, this is the flattener that was designed for the job.
