The Field Flattener for Short Refractors by Orion:

Optically fast refractor telescopes used for astrophotography 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. Orion's handy field flattener resolves the issue by providing excellent field correction while preserving the focal length attributes of your telescope. Designed for use with refractors with focal lengths of 400 mm to 650 mm 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 telescope. 

Fully multi-coated, 38 mm clear aperture optics and a glare-reducing threaded interior ensure maximum image contrast. Backfocus of 55 mm 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-ounces.

 

Orion Field Flattener for Short Refractors Features:

• Eliminate field curvature in short, optically fast refractor telescopes with this handy 38 mm clear-aperture, fully multi-coated field flattener
• Designed for use with 400 mm to 650 mm focal length refractors with f/5 to f/7.5 focal ratios
• Optimizes your fast refractor telescope for astrophotography
• Preserves focal length attributes of the attached refractor telescope while flattening the field of view
• Requires 55 mm of refractor telescope backfocus, weighs 7.5-ounces

OPT Product Number: OR-08893