Ultratelephoto 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.