My only consolation is that I did figure out something with my DSLR lens. I really wanted to get it onto my ASI2600MC, but the Canon lens to M42 adapter I have (the only one I could find) is too long so I couldn't get the image in focus. It works with my ASI678MC, so I had to settle with that for the moment.
I really want a very short (sub-100mm focal length) lens for my astro cams with a locking focuser, but I don't know how to find one. DSLR lenses aren't ideal.