"The Digi-T system is quick, secure, and easy to use.Less Vignetting - When coupling a digital camera to a telescope it is imperative that the eyepiece lens and the camera lens are as close together as possible, a separation of even 1/2"" will result in an image like looking through a soda straw. When installed onto the eyepiece Digi-T is flush with the top. Thanks to Digi-T's exclusive ""thread-through-thread"" design the step ring then threads completely over it, adding zero length. No other adapter gets as close!Fits More Eyepieces - There are 2 types of conventional eyepiece projection adapters, fixed length and variable. The fixed length adapters are too short to hold the most popular eyepieces (such as the 26mm Super Plossl) and too narrow to hold many others. The variable length adapters are designed for film cameras and are simply too long to allow the close coupling necessary for digital cameras, in addition they are still too narrow to hold any of the wider field eyepieces. Digi-T fits a 4mm Plossl or a 40mm Plossl!No Back Focus Problems - All conventional eyepiece projection adapters have one thing in common, they lift the eyepiece up in the holder by about 1"". For many refractors and reflectors this is a serious problem as they can no longer reach focus! This is especially true with the popular ETX60/70 telescopes. Since Digi-T attaches to the top of the eyepiece it doesn't change the eyepiece position at all and focus remains the same."