Optimised for Sky-Watcher superfast f/4 Quattro imaging Newtonians, delivering stunning wide-field views with pinpoint stars to the edge of the flat field. Magnification remains unaltered. Features a 4 x element design with one element made from FPL51 ED glass. Requires 55mm back focus. Image height 28mm. Outside diameter 50.8mm. A suitable M48x0.75 adapter is required to match your camera. Sky-Watcher manufactured Canon and Nikon M48x0.75 adaptors are available.