The William Optics FLAT6AIII for the Fluorostar 91 refractor brings imaging to the next level of adjustability and image quality. This 0.8X field flattener uses Ohara optical glass in an FMC Triplet APO design for amazing clarity and sharpness. The William Optics FLAT 6AIII adjustable Focal Reducer & Field Flattener has an image circle large enough to cover full frame, 43.26 mm diagonal sensors!

The FLT91 version of the FLAT6AIII has M92 threads on the focuser side and M48 threads to accept a larger M48 T-ring and camera. There are M48 threads inside that will accept filters as well.

The adjustable distance for DSLR's and mirrorless cameras is 5.4 mm.