Celestron"s EdgeHD 8 Optical Tube is a Aplanatic Schmidt Telescope design. * The EdgeHD 8 has Fastar Versatility. * The EdgeHD has superior edge performance with its StarBright XLT Coatings. * Celestron"s Edge HD 8 Optical Tube lets you see the Universe in HD and is the most versatile imaging * 8" EdgeHD Optical Tube Assembly