Has anyone here used the PF-CA25? It's an adapter to mount a Pentax SLR to a spotting scope or other optic that usually uses an eyepiece. It's like a f12 fixed, and it's very spendy... but all this lunar photography reminded me of my 15-45x spotting scope, and it sure gets you closer than the 200mm lens I have. I just don't think I can justify dropping $400, when the scope only cost me $60! (it's an old used bushnell)
I did some playing around though, and I think you could actually jimmy rig something to use the existing eyepiece. I was able to get it to focus by just taking the lens off and holding it very close to the eyepiece. Similar idea to the P&S adapters for scopes.
Pentax | PF-CA35 K-Mount SLR Camera Adapter | 70510 | B&H Photo