Mount up! Celestron"s T-ring allows you to attach your 35mm, Canon EOS, SLR camera to the prime focus of your telescope or spotting scope. This arrangement is used for terrestrial photography and short-exposure lunar and planetary photography. It can also be used for long-exposure deep-sky photography when you"re using a separate guide scope. Both the T-ring and a T-adapter (sold separately) are required to attach your camera to a telescope. * Ideal for astrophotography * Attaches a camera to the main focus of a telescope * Used for terrestrial, lunar, and planetary photography * Can also be used with a guide scope for deep-sky photography