A 2” diagonal is required if you want to use 2” eyepieces when observing with your SCT or EdgeHD telescope. The larger 2” barrel allows you to see a bigger percentage of the telescope’s light cone, ideal for capturing faint deep sky objects with low surface brightness. A diagonal is also an integral part of the optical chain and a good diagonal can make a big difference in the quality of the image you see.
The Celestron 2” Mirror Diagonal was built for superior performance. It's housing is precision machined in order that the optics stay perfectly aligned. The diagonal’s mirror is tested with an interferometer, and is guaranteed to be 1/10 wave or better. The mirror’s surface is covered with the same high performance XLT coatings used on Celestron’s best telescopes. The result is a sharp, bright image that will satisfy the most discriminating amateur astronomer.
This 2” diagonal threads securely to the rear cell of standard Schmidt-Cassegrain/Edge HD telescopes. To take advantage of the XLT Diagonal’s extra light throughput, insert a 2” eyepiece into the barrel. If you want to use 1.25” eyepieces, slide the included 2” to 1.25” adapter into the eyepiece barrel and secure it with the thumbscrew. When you’re not observing, store your diagonal in the included aluminium case for protection.