I'm not at all familiar with afocal photography which what I believe you would need with your camera. Have a look at
http://www.televue.com/engine/page.asp?ID=237 and perhaps also others may chime in with some help.
I would say that the things that would affect image scale would be telescope focal length, eyepiece focal length & camera lens focal length. Tele Vue call it digiscoping and have a list of eyepices on the following table (last column)
http://www.televue.com/engine/page.asp?ID=144 They also sell eyepiece to camera lens adaptors. (Talk to BINTEL being Tele Vue distributor in Aus).
It looks like long eye relief eyepieces work best and there are suppliers (also try BINTEL) that sell eyepieces that are specifically designed for afocal photography (digiscoping) and are called projection lenses.