Astro-Tech 1.0x Field Flattener for AT115EDT Refractor (V3) – AT115EDTFFv3
Precision-engineered to pair with the Astro-Tech AT115EDT f/7 triplet apo, the AT115EDTFFv3 1.0x field flattener turns your 115mm refractor into a full-frame-ready imaging system—without changing your native focal length. Built to thread directly into the 3.2" focuser, this third-generation flattener delivers pinpoint stars edge-to-edge and a generously illuminated image circle up to 60mm.
Native Focal Length. Flattened Field. Big Results.
The AT115EDTFFv3 doesn’t alter the optical speed or scale of your scope—your 805mm f/7 system remains intact. What it does do is flatten the field curvature inherent in fast refractors, giving you tight, round stars all the way to the corners of DSLR and CMOS sensor arrays, even on full-frame chips.
If you’ve ever had to crop the corners out of an otherwise perfect image, this is your solution.
Huge Corrected Image Circle—Up to 60mm
This isn’t a repurposed small-chip flattener. It’s optimized for serious imaging, with correction and illumination across an expansive 60mm image circle. While M48 and M54 threaded adapters will clip the outermost edge of that circle, the large clear aperture and M78x1 thread option give advanced users room to build out larger-format systems.
It threads directly onto the M92 drawtube of your AT115EDT’s 3.2" focuser—no extra adapters required.
Three Threaded Camera Connections + Hidden Filter Thread
On the camera-facing side, the flattener includes three threaded connection options:
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M78x1 female
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M54x0.75 male
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M48x0.75 male
Even better: the upper cell unscrews to reveal an internal 2" filter thread, allowing you to use any standard 2" filter inline—perfect for light pollution suppression, L-eXtreme-style narrowband, or LRGB setups. It’s a clean, compact alternative to bulky filter drawers or wheels.
Designed for 55mm Back Focus
From the shoulder of the flattener to your imaging sensor, the required spacing is the industry-standard 55mm, ensuring compatibility with most T-rings, spacers, and camera adapters. The assembly is fully multi-coated for high contrast and minimal ghosting, and it includes thread-on caps for both ends to protect your optics in storage.
Observing Tip
If you're shooting broadband under dark skies or narrowband under light pollution, take advantage of the internal 2" filter thread to streamline your setup. A 2" dual narrowband filter can be permanently installed and protected inside the flattener—keeping your imaging train short, simple, and free from flexure.
Final Thoughts
The AT115EDTFFv3 is a simple, elegant solution for serious astrophotographers using the Astro-Tech AT115EDT. It preserves your focal length while correcting the field, supports full-frame sensors with ease, and integrates filter functionality without extra hardware. If you’re ready to unlock the real potential of your imaging refractor, this is the piece you’ve been missing.
