The moon is always there, or at least it is there often enough, to be a test subject for a long lens. Here's my 500mm f4 with a 2x extender, on a DSLR of course.

One day past full

I think the result is somewhat sharper than the digiscoping setup with the telescope. Of course where a telephoto lens really outshines a telescope is the edge-to-edge sharpness, something I really noticed when trying to use the scope to shoot eagles. That's not important with the moon photo because the edges are black. Where the telescope has an advantage is the ability to provide greater magnification, but I would need to get additional attachments to do serious astrophotography.

Camera lenses are great for taking photos, and telescopes are great for looking through, and trying to use one in place of the other does not provide the best results. It's only taken about 10 years for me to figure that out.