This precision 90° star diagonal for telescopes features fully coated prisms, delivering superior image fidelity. Its 90-degree shape makes it perfect for nighttime stargazing, since it places the telescope eyepiece at a comfortable viewing angle. The Orion 1.25" Prism Star Diagonal's eyepiece holder is made of machined aluminum and its nosepiece is a chrome-plated metal barrel that's threaded for like-sized 1.25" eyepiece filters. The eyepiece holder has a setscrew for locking the telescope eyepiece securely in place. This diagonal produces an image that is right-side up and reversed left to right (therefore, not recommended for terrestrial observing). Diagonals are not recommended for use in reflector telescopes. Fits in 1.25" telescope focusers and accepts 1.25"-diameter eyepieces.