William Optics 0.8X Reducer & Field Flattener for FLT91 - FLAT6AIII-M92 31mm Eyepieces The doublet front group is

The doublet front group is made of FPL-53 glass

They also excel at lunar and planetary viewing - as well as terrestrial objects

you're not just looking at the stars – you're swimming in a sea of stars

Safety Warning - How to Protect Your Eyes (link to Safety Information)

and each Omni goes through a two-step anodizing process to prevent reflection from the top eyepiece barrel

William Optics 0.8X Reducer & Field Flattener for FLT91 - FLAT6AIII-M92 31mm Eyepieces The doublet front group isThe 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