This precision 90° star telescope diagonal from Orion features fully-coated prisms, delivering superior astro-images. Housings are plastic with thumbscrew to secure the eyepiece in place. This 90° diagonal yields correctly oriented images (right-side up and non-reversed). It's perfect for terrestrial use or for beginner astronomers who want a view that matches the orientation of a star chart. Requires no extra focus travel. This diagonal is not to be used with reflector telescopes.