This 2” dielectric mirror-type star diagonal is an outstanding value. At this low price, if there ever was a bargain in astronomy, this is it.
This 2” Astro-Tech first-surface mirror star diagonal has state-of-the-art 46-layer dielectric mirror coatings for a full 99% reflectivity, higher than the 88% of a conventional aluminum diagonal or the 96-97% of an easily-tarnished silver diagonal.
The durable ion-deposited dielectric coatings on the mirror’s finely-polished 10mm thick 1/10th wave BK7 optical glass substrate also provide higher contrast and resolution during critical planetary, lunar, and binary star observations.
The supplied 1.25” eyepiece adapter uses a compression ring to hold eyepieces in place. The scope-side barrel of the 1.25” adapter has a subtle slanted groove to keep it from accidentally slipping out of the 2” diagonal. Dust covers are provided for the 1.25” adapter and the diagonal’s 2” barrel.
The interior of the diagonal body and the inside of the focuser-side barrel are treated with light absorbing materials. The focuser-side barrel is also internally anti-reflection threaded for even higher contrast. The barrel is threaded to accept standard 2” filters.
A subtle slanted groove cut into the outside of the focuser-side 2” barrel engages with your telescope’s focuser thumbscrew to act as a safety stop. This keeps the diagonal from falling should the scope’s thumbscrew loosen slightly from cold or use.
This diagonal is a visible improvement over the conventional 2" diagonal provided with many refractors capable of using 2” optics. It can also be used with a Schmidt-Cassegrain or Maksutov-Cassegrain telescope with a suitable adapter, such as the #7785C. It is an absolutely premium 2” 99% reflectivity dielectric self-centering star diagonal at a fraction the price of competitive models with equivalent performance and build quality. The same performance, for as little as half the price. If there ever was a bargain in astronomy, this is it.
