The Askar 65PHQ 0.75× full-frame reducer has a quadruplet design. The 0.75× reduction gives 65PHQ a shortened focal ratio of f/4.8 and a shortened focal length of 312mm. This reducer, connected with the astrograph, can effectively shorten the exposure time and dramatically increase your field of view, bringing more convenience and possibilities for your deep-sky astrophotography. The backfocus is the standard 55mm. It comes with two thread adapters of M54, M48 with a built-in M48×0.75 2” filter thread, so it is convenient for connection.