Review on 🔭 SVBONY 1.25-inch 90° Zenith Diagonal Mirror for Refractor and Cassegrain Telescopes – Astronomical Telescope Accessory by Jasmine Jimenez

This is not a diagonal, it's a diagonal. Bought for my Celestron C90 Maxutov and it has worked well so far. *The image it provides while the corrected "upside down" is reversed from "left to right", so don't use that diagonal if your main need is a fully erected/corrected image. * Since it is a mirror, it adds a third reflective surface. to the optical path of the Maksutov telescope. If you want the optical perfection of a prismatic star diagonal, this isn't it.