Thanks Ross & Eden. You may be right that the short backfocus distance is the reason that this is not produced for E-mount lenses. If I have to pay $250 for an adaptor, I'd be better going down the suggested path of getting a 'native' M42 lens, such as a Pentax, or maybe the Canon/Olympus route.
A thought that occurred to me - for something like a QHY CCD, how would one mount it when not attached to prime focus? I guess tube rings around the lens?
