Hi Hans
That's a fairly common back focus distance. Just get a 21mm and 16.5mm adapter. I'm guessing the camera has an M42 thread? (I looked but couldn't see info on it)
edit:
e.g.
21mm (screws into the camera and the below)
https://www.bintel.com.au/product/zw...v=322b26af01d5
16.5mm (M48 side screws into the scope and M42 screws into the above)
https://www.bintel.com.au/product/zw...v=322b26af01d5