Orion 8893 Field Flattener for Short Refractors

Optically fast refractors used for astro-imaging are often plagued by significant field curvature, which is especially noticeable when using CCD imagers with APS-C sized and larger sensors, or DSLR cameras. Our handy field flattener resolves the issue by providing excellent field correction while preserving the focal length attributes of your scope. Designed for use with refractors with focal lengths of 400mm to 660mm and focal ratios of f/5 to f/7.5, the Orion Field Flattener for Short Refractors lets you enjoy the full imaging potential of your fast refractor. Fully multi-coated, 38mm clear aperture optics and a glare-reducing threaded interior ensure maximum image contrast. Compatible with 2" focuser drawtubes. Conveniently threaded for use with 2" filters. Backfocus of 55mm is required, we recommend using the Orion T-thread Spacer Ring Kit (sold separately) to achieve proper distance for use with CCD imagers. Use with a DSLR requires a T-ring for the camera (T-ring sold separately). Weighs 7.5 oz.