This useful adaptor screws on to the visual-back (the 2" thread on the rear cell of an SCT) and allows prime-focus astrophotography. To attach your camera you will need a T-ring adaptor for your particular brand of camera, this is not included but is readily available from camera shops. It will also hold 1.25" eyepieces and accessories (star diagonal etc) and has the usual thumb screw for this purpose.