How do I use the visual back and StarDiagonal with my NexStar SE Schmidt-Cassegrain telescope?
October 27, 2008
The major accessory for visual use with a SCT is called the visual back. It screws right on to these threads on the back of the tube and allows you to use standard 1.25 inch eyepieces. Two setscrews hold accessories in the visual back.
While you can put an eyepiece directly in the visual back, most of the time you want to use a StarDiagonal or diagonal for short, which is a prism or mirror in a double-ended tube that allows more comfortable views looking down or sideways instead of straight through the back of the SCT. One end goes into the visual back; the other end holds your eyepiece in place with a setscrew or setscrews.
Note: Be careful not to unscrew the telescope end of the diagonal by turning it when the setscrews of the visual back are tightened. This also applies for the eyepiece tube, as it may also become loose when turned in the diagonal if the diagonal’s setscrews are tightened.