As Eric says Henry, If at Prime (Or Newtonian to be exact) focus, your
DSLR doesn't focus due to lack of inward travel and all other options
won't work either..ie low profile focuser....and the drastic measure of
doing the tube chop is off the cards, then another option is introducing
some magnification before the camera. IE barlow or Televue Powermate
or even eyepiece projection.
This presents a few bigger problems for you as well. Nothing comes easy
in this hobby eh?
Focus is now a problem due to usually not having enough OUTWARD
travel because the Barlow or Teleview lengthens your effective
focal length.
With only minimal power it should still be able to focus , if not
then an extension tube of 25mm or 50mm will get you back within a
focusable range....BUT...
Your drive needs to track better if you intend to do
any long exposure and your mount needs to be polar aligned.
However some people have obtained fantastic results with hand
guided planetary/ moon stuff with some barlow power added between their
scope and camera/webcam etc.
The moon is a great first target for this as you have lots of brightness
and the webcam will auto adjust to a fast frame rate to minimise your
hand shake with hand guiding....or just letting it drift due to us spinning.
I think some of Mike S' first Jupiter stuff was hand guided, I might be
wrong here. He also did some fantastic stuff hand guiding on the International
Space Station with his DK21 camera (basically a souped up webcam).
Hope this helps.
Steve