Stellarvue 3-Inch 0.8X Reducer Field Flattener for SV115 Refractor:Â The Stellarvue SFFR115-3FT Reducer Flattener is optimized for use with the SV115 that sports a 3" Feather Touch Focuser. The SV Reducer Flattener threads into the 3" FT focuser. A 48 mm filter thread is machined into the reducer flattener, allowing you to add standard 2-inch filters when desired. The focal reduction of the SFFR115-3FT is 0.8X, which converts the focal ratio of your SV115T to f/5.6.
The backfocus of the Stellarvue 3-Inch Reducer Flattener 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 SVR115T's 3-Inch Feather Touch 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 camera's 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).