Ultra Flat 91 (0.79x Reducer)

Description

The William Optics Ultra Flat 91 is a 0.79x focal reducer and field flattener designed for the Cat 91 and similar 91mm William Optics telescopes. It reduces the focal length by 21%, resulting in a faster focal ratio and wider field of view while maintaining a flat, corrected field across the image plane. This is essential for astrophotographers using full-frame or APS-C sensors who want sharp stars from corner to corner.