Orion Field Flattener for Short Refractors

Eliminates field curvature in short, optically fast refractor telescopes, for sharper stars Designed for use with 400mm to 660mm focal length refractors with f/5 to f/7.5 focal ratios Now includes interchangeable male M42 and M48 "wide" thread-on camera adapters (T-ring for your camera sold separately) Preserves focal length attributes of the attached refractor telescope while flattening the field of view Compatible with 2" focusers and requires 55mm of backfocus Optically fast refractor telescopes used for astrophotography are often plagued by significant field curvature, which is especially noticeable when using CCD/CMOS imagers and DSLRs with APS-C sized and full-frame sensors. This manifests in stars that are out of focus on the periphery of the image frame. Orion's handy field flattener solves this problem by providing excellent field correction while preserving the focal length attributes of your telescope. With the field flattener, stars will appear in sharp focus across the e