Astro-Tech Dielectric Quartz Mirror Diagonal

Quartz has a much lower coefficient of thermal expansion than standard glass. This means the mirror holds its precise shape better as temperatures drop during a long night of observing, which helps maintain your focus stability.

This is a 1.25-inch diagonal, designed specifically for refractors and catadioptric telescopes that accept 1.25-inch accessories. It will not fit 2-inch focusers without a separate adapter.

The brass compression ring provides a secure, even grip on your eyepiece barrel without using a metal set screw that can scratch or mar the surface. It is a much safer, more durable way to hold your expensive eyepieces in place.

Yes, especially when viewing faint deep-sky objects. Compared to standard aluminum coatings that typically reflect around 88-92%, the 99% reflectivity of these dielectric coatings delivers a noticeably brighter, higher-contrast image.

Yes, the nosepiece is threaded to accept standard 1.25-inch astronomy filters, allowing you to easily swap out color or nebula filters without removing the diagonal from the telescope.

Absolutely. The interior is finished with anti-reflective matte black anodizing, which is essential for absorbing stray light and ensuring you get the maximum possible contrast in your views.