TPO 2" Mirror Diagonal with SCT Thread - Deluxe Dielectric

  • The TPO Deluxe Mirror Diagonal is manufactured with 99% reflectivity and dielectric coatings.
  • The BK7 mirror os polished to minimum 10th wave.
  • The TPO Deluxe Mirror Diagonal attaches to rear cell thread of Schmidt-Cassegrain/Maksutov-Cassegrain telescopes.
  • Fully CNC machined housing and includes 1.25 inch adapter.
  • Brass compression rings on both the TPO Deluxe Mirror Diagonal and adapter assure gentle treatment of your eyepieces.
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  • Regular price $123.95

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TPO 2" Mirror Diagonal with SCT Thread - Deluxe Dielectric

The TPO 2 inch dielectric mirror diagonal features 99% reflectivity, dielectric coatings to maximize light output of your telescope system. Our custom made diagonal uses a BK7 mirror polished to 10th wave accuracy or better for best possible image quality.

The TPO 2 inch dielectric diagonal also features a CNC machined housing. This housing is designed to retain the optimal collimation of the mirror and assure the best optical performance. The CNC machined aluminum housing will provide outstanding results for years of use.

This diagonal also includes brass compression rings on both diagonal and the included 2 inch to 1.25 inch adapter, assuring gentle treatment of your eyepieces. Some other brands use set screw locking mechanisms that can mar the barrel surface of your favorite eyepieces. Avoid scratches and gouges by using the OPT dielectric series diagonals.

TPO dielectric diagonals provide outstanding performance with low prices to provide amateur astronomers with excellent value! TPO backs this diagonal with a full 2 year warranty against manufacturer defects, which may be expanded into a lifetime warranty by purchasing a warranty extension.

This diagonal attaches to the rear cell of SCT's. It is not meant for SC telescopes that have an electric focuser attached to the rear cell. In these instances, we recommend the TPO 2 inch Mirror Diagonal.



Angle90 degree
Diagonal Barrel SizeSC Thread (2"x24)
Free ShippingYes
Warranty2 Year Warranty
Customer Reviews
4.5 Based on 2 Reviews
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WOW! What a Differenec!

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!

Albuquerque T.
Good Quality Diagonal with a Few Caveats

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.