With high-end telescope systems, many observers prefer to use a good-quality mirror star diagonal rather than a prism diagonal. The mirror in this 2" Orion Refractor Mirror Star Diagonal is carefully polished to provide users maximum performance. Housing is made of black-anodized aluminum and the barrel is internally blackened. This 2" diagonal accepts both 2" and 1.25" eyepieces (with included adapter). The 2" eyepiece holder has two locking setscrews for maximum eyepiece security. This telescope diagonal renders images that are right-side up and reversed left to right (therefore, not recommended for terrestrial observing). Diagonals are not suitable for use with Newtonian reflector telescopes due to insufficient focus travel.