I bought this diagonal several weeks ago to replace the Celestron 2 diagonal that I had been using. Last night, I got the scope out to try my new CGEM-DX mount and had forgotten that I had the new diagonal that I'd never used. I was VERY pleasantly surprised when I looked through the eyepiece. The brightness and contrast of everything I looked at was much better than I'd ever seen. The stars of M13 were so bright and crisp! I suddenly remembered that I'd bought this diagonal and knew that it was $110 well spent. I'm very happy with this purchase. (The CGEM was awesome as well!

During my transition to 2” eyepieces with my Celestron C11 SCT (F/10 I wanted a good quality, 2” diagonal with high reflectivity that didn’t cost me an arm and a leg. This diagonal definitely has a high quality feel to it and my views were clearly improved over my existing 1.25” Celestron diagonal. The only negative I experienced was during the necessary step of rotating the diagonal to get in a comfortable eyepiece position while viewing objects at different points in the sky. I prefer using a standard diagonal (without threads held in by thumb-screws/compression rings. That setup is much easier and quicker to adjust in that you loosen the screw, rotate the diagonal, and tighten it down again. It got to be a pain to loosen the SCT threads and tighten them again every time I wanted to rotate the diagonal. Another caveat is that while this diagonal is a great option for an 8” or smaller SCT, it may not be the best choice for 10” and larger SCTs. This is because the standard 1.5” SCT threads are smaller than the light path of 10” and larger SCTs as well as the field stop opening of most long focal length 2” eyepieces. This cuts off part of the light cone causing you to lose precious light. No big deal if all you care about is planetary or lunar viewing, but very important for “faint fuzzy” viewing and avoiding vignetting. I returned this product and got the 2” version of this diagonal without SCT threads. I also replaced the 3.25”-to-SCT thread adapter on the back of my C11 with a 3.25”-to-2” adapter from Astro-Physics that would accept a standard 2” diagonal. Now my light path is un-obstructed and I’m very happy using 2” wide-field eyepieces. Clear Skies.