Skywatcher telescope coma corrector, optimized for the super-fast f/4 Quattro Photo Newton, they deliver an impressive image of needle-point fine stars up to the edge of the flat field of view. The magnification is retained. The system consists of 4 lenses with an element of FPL51 ED glass. The back focus is 55 mm, the image circle diameter is 28 mm for APS-C format. The coma corrector has a plug-in diameter of 2″. To attach your camera you need an adapter from M48x0.75 to your camera connection. Sky-Watcher offers adapters for Canon and Nikon. (Prod. Code 20237 & 20238) Scope of delivery: Koma Corrector dust caps !Power supply and batteries are not included!