The Celestron SCT 2″ XLT Mirror Diagonal is an excellent star diagonal made specifically to thread to the rear cell of Celestron 5″, 6″, 8″ and 9.25″ Schmidt Cassegrain Telescopes. It is a solid diagonal, and has an excellent anodized, matte black finish. The excellent construction is what stood out to me most when I first purchased the diagonal.
This diagonal utilizes Celestron’s Starbright XLT coatings to give a mirror that reflects about 96% of incoming light. These excellent coatings allow more light to reach your eye, which helps increase the surface brightness of faint deep sky objects. Since using this diagonal, I have been able to better resolve the stars in Globular Star Clusters, and have had an easier time resolving faint Planetary Nebula, such as the Ring Nebula.
In addition to the build quality and excellent coatings, the diagonal allows 2″ eyepieces to be used. 2″ eyepieces will allow the user to delve into more of their Schmidt Cassegrain’s light cone than 1.25″ eyepieces will. This also increases the amount of light that reaches your eye, making it easier to resolve dim objects.
Having the ability to use 1.25″ eyepieces and 2″ eyepieces really makes the Schmidt Cassegrain Telescope a versatile instrument. Couple that with the build quality and coatings on this diagonal, and you have an excellent product from Celestron.