The Tele Vue RFL4087 0.8x Field Reducer and Flattener reduces your telescope focal length and speeds up the focal ratio by 20% while flattening the lens curvature to capture clear and sharp images during prime-focus astrophotography using formats up to 35mm. It can be used with Tele Vue TV102 and TV102iis OTAs and is optimized for the 55mm back focal length that is typical of DSLR camera bodies. It will also work on non-flat-field 800-1000mm focal length refractors outfitted with 2" focusers. A camera-specific T-mount is required to properly mount the camera body.
The RFL4087 has a 2.4" diameter female-threaded front to work with their own IS system focuser, and you simply screw the RFL4087 reducer into the back of the optional RAD1074 nosepiece adapter to use with the TV-102 or any other normal 2" focusers. For the TV102iis OTA the front female threads accept the optional TLA-0250, TLB-0375, TLC-0500, or TLD-1000 threaded extension tubes; as they are necessary to function properly with the OTA's focuser. Depending on the specifications of the camera or imaging system being used, additional optional spacers and tubes may be required to achieve the correct back-focus distance to the imaging sensor.