William Optics Flat7A Adjustable Flattener Reducer

William Optics Flat7A Adjustable Flattener Reducer: flat field and 0.8x focal reduction in one

The William Optics Flat7A combines two functions: it flattens the image field and shortens the focal length by a factor of 0.8x. Every refractor naturally produces a slightly curved image plane; a flat camera sensor cuts through that, causing stars in the corners to stretch into streaks. A flattener corrects this curvature so that stars remain small and round all the way to the corners. The reducer also makes your telescope one stop faster: shorter total exposure time for the same result.

The optics are a triplet made of Japanese Ohara glass with a full FMC coating: maximum sharpness and contrast, minimal reflections. Made for refractors from f/5 to f/7 and calculated for large DSLR sensors.

Adjustable, without loose extensions

You mount the Flat7A directly onto the M92 thread of your focuser and adjust the distance to the optics with the adjustable locking ring. No fussing with spacer rings: twist, lock, done.

The camera train

The camera side is T2, for the T2 ring for your camera brand. The 45 mm extension tube positions the sensor at the calculated distance, and the integrated M48 filter thread accommodates your filter in the assembly.

Featured accessories

Combine the Flat7A with the 45 mm Flat68II/Flat7A adapter and the T2 ring for your camera brand for a complete, tilt-free setup.

For whom yes and for whom no

• ✓ Astrophotographers with an f/5 to f/7 refractor with M92 focuser
• ✓ Who wants speed gain and field correction in one element
• ✗ Owners of focusers without an M92 connection: check your thread size first

Specifications

You can find more accessories for this brand at the William Optics brand page.