The celestron t adapter for nexstar 4se telescopes is a sturdy aluminum t adapter for when you'd like to attach an slr or dslr camera to the smaller rear cell threads of a celestron nexstar 4se telescope or c90 spotting scope for prime focus photography. To get started you will need the appropriate t ring for your camera body 93402 for nikon 93419 for canon eos. First you remove the lens from your camera and attach the t ring in its place. As the t ring is camera brand specific, it will snap right on just like a lens. Next, remove the diagonal and visual back from the rear cell of your telescope and screw the celestron t adapter onto the rear cell threads until secure. Now, thread the t ring camera onto the t adapter. The camera is now using your telescope as a telephoto lens. Prime focus photography is popular for short exposure images of terrestrial objects as well as celestial objects like the moon.