The Askar FRA400C 0.7x full-frame reducer features a triplet lens design specifically for the FRA400C. Reduces the focal length to 280mm and focal ratio to f/3.9 while providing flat-field correction. Standard 55mm back focus with M48×0.75 rear adapter and built-in 2" filter thread. Enables wider field of view and faster exposure times for deep-sky imaging.