A Visual Back is a metal adapter that screws onto the standard rear cell threads of Schmidt-Cassegrain and Maksutov-Cassegrain telescopes and accepts 1.25” accessories, including diagonals, eyepieces (for straight-through viewing), Barlows, webcams, and any other accessory with a 1.25” insert barrel. All Celestron 5”, 6”, 8”, 9.25” and 11” Schmidt-Cassegrains come standard with the 1.25” Visual Back. To use 2” diagonals on a Celestron 5” - 11” Schmidt-Cassegrain, remove the visual back and thread on a 2” diagonal made especially for Schmidt-Cassegrain telescopes, such as the Celestron 2” XLT Diagonal (#93527).