Star diagonal mirror for astronomical telescopes provides a comfortable 90-degree viewing angle, essential for observing objects near the zenith. Features a standard 1.25-inch barrel size compatible with most refractor and Schmidt-Cassegrain telescopes. The durable black composite body includes a chrome-finished insertion tube and a secure thumbscrew to hold eyepieces firmly in place. This essential optical accessory utilizes a high-quality internal mirror to redirect light, ensuring bright and clear upright images for celestial viewing.