The Stellarvue SFFR102-2 Reducer Flattener is optimized for use with f/7 refractors with a standard 2" focuser. The SV Reducer Flattener slips into the 2" focuser and is snugged into place with the focusers set screws. A 48 mm filter thread is machined into the reducer flattener, allowing you to add standard 2" filters when desired. The focal reduction of the SFFR102-2 is 0.8X, which converts your f/7 refractor to f/5.6.
The backfocus of the Stellarvue 2" Reducer Flattener for f/7 Refractors is 55 mm. Since a DSLR with t-ring has a 55 mm backfocus, it is a simple matter to use the reducer/flattener for DSLR imaging. Just insert the reducer/flattener into the telescopes focuser and then thread the camera/t-ring combo onto the flattener. An example is shown in the additional images section to the left.
If you will be imaging with a CCD camera as opposed to a DSLR, extension tubes may be required to achieve focus. It is important that you know the distance between your cameras t-thread and the sensor, and it is equally important to remember that the distance from the back of the field flattener/reducer to the CCD sensor remains at 55 mm. If the CCD camera, for instance has a backfocus of only 35 mm, a 20 mm extension will be needed. If any extension tubes are required for your set-up, they will thread between the camera and the field flattener, as shown in the example provided in additional images. Please note that the camera side of the reducer/flattener requires extension rings with a standard t-thread (M42x.75).