"Ultra telephoto photography is easily achieved with your Geoma spotting scope by purchasing the Vixen SLR Camera Adapter G. Unlike most of these devices, the Camera Adapter G allows you to shoot through an eyepiece (instead of using the scope, without eyepiece, as a prime focus SLR lens). Since the fastest effective aperture is only f/10.7, it is only practical to use the Camera Adapter G in bright light and at a very high ISO setting. Thankfully, the ability of modern DSLRs to render noise-free high-ISO images still makes the adapter G quite useful-it isn't for a film SLR.The Camera Adapter G can only use the Vixen GL15, GL20 and GL25 eyepieces. There is a built-in extension ring which can lengthen the effective focal length of your scope/eyepiece combination.The effective focal length gets awfully long awfully quick using this adapter, so to get good results you'll need to take every precautions at your disposal to minimize vibration: lock up the SLR's mirror (if possible) just before firing, use a cable release or remote control to fire the shutter and use a sturdy tripod. Vibration suppression pads would also help quite a bit.To use this adapter, first remove the eyepiece. Next, attach the SLR camera adapter where the eyepiece would normally be attached to the spotting scope. Screw in a t-mount adapter to the opposite end of the SLR camera adapter; now you can attach your camera to the t-mount and you are ready to begin taking pictures.|Allows extremely high effective magnification telephoto photography|Captures images with SLR through a Vixen GL15, GL20, or GL25 eyepiece|Your camera's specific T-mount adapter is required"