Celestron EdgeHD 1100 CGEM Schmidt-Cassegrain Telescope Celestron 11" aperture aplanatic Schmidt-Cassegrain telescope produces astrograph-quality flat focal plane EdgeHD coma-free Cassegrain optics and a built-in field flattener ensures sharp focus all the way to the edge of the field Flexible tension clutches hold the mirror in place and reduce image shift when rotating the tube around the mount Cooling vents located on the rear cell allow hot air to be released from behind the primary mirror All EdgeHD optical tubes are Fastar compatible for imaging down to f/2 with optional accessories