1.    The proprietary FLI nosepiece is a short extension, 2.925" in diameter. It has a v-groove around the perimeter, .157" from the face, and an engagement of up to 0.300". All FLI nosepieces also have an internal SC thread, with the usable depth shown in the table above. Mating parts should be fabricated with a 2.930" x 0.280" pocket, and two set screws located .124" from the face of the pocket. Contact FLI for additional information. Use of the FLI nosepiece and receptacle insures the shortest possible path length.

2.     T-threads are standardized to M42-.75 and are generally compatible with other t-thread products.

3.    The SC (Schmidt-Cassegrain) thread is not standardized. Though referred to as a 2"-24 thread, many manufacturers of tubes and accessories cut this thread slightly oversize. The result is that many externally threaded SC parts will not screw into correctly sized 2"-24 internally threaded parts. FLI specifies all SC externally threaded parts as 2"-24, and most SC internally threaded parts as 2.012"-24. This is less than ideal since it results in a somewhat loose fit, but it insures compatibility with 3rd party products.

4.    C-mount is the video lens standard and is a 1"-32 thread. Flange to focal plane distance is 17.5mm. Consult FLI regarding C-mount cameras.

5.   CS-mount is a short version of the C-mount. The threads are the same, but the flange to focal plane distance is 12.5mm. FLI does not support the CS-mount.

6.    The back focus of a lens is defined as the distance from the vertex of the rear element to the focal plane when the lens is focused at infinity. This is not the same as the flange to focal plane distance. Be sure that lens elements and related parts do not interfere with the camera shutter.

7.    FLI 2" tubes are threaded to accept 48mm filters.