Antares 0.7x Focal Reducer for F/10 or Higher Telescopes - FR2-0.7

The Antares FR2-0.7X is the same 4-element f/6.3 lens system used for f/10 Schmidt-Cassegrain telescopes but in a 2" barrel threaded for standard filters. It is recommended for increasing true field in telescope with f/ratios of f/10 or higher. Focal length reduction is around 0.7X, but the exact reduction factor depends on the lens positioning between the objective and image plane.  

For F/10 systems. spacing from the back of the focal reducer element of SCTFR/0.7X to image plane: 

f/6.3 = 86mm

f/7  = 71mm