The Lumicon, LD1010, 1.25" Enhanced Aluminum 90° Diagonal reflects 96 to 97% of the light from the telescope's primary optics directly into your eyepiece. In this way, you'll hardly lose anything from what your telescope sees. It may also be used on refractors and SCTs (Schmidt-Cassegrain telescopes).

Lumicon collimates each diagonal mirror via a double-pass collimator, ensuring that the light reflected from the diagonal is perfectly perpendicular to the telescope's optical axis.