There's a very low-tech solution if you're willing to score your lenses. Only tiny marks - all my lenses are scored for focus at the various widefield zooms I use. If you can auto-focus on a bright object like the Moon, this will also be good focus at widefield (say, 18mm up to 50mm)for the starry background. At a tighter zoom of say 200mm you can auto-focus on the brightest stars (the very brightest) or planets, using the centre focus box. I used a Stanley knife to do the score marks - a bright LED light shone sideways across the scores will enable precise alignment using manual focus.
Simple but effective, but I would bet that a lot of people would regard this as sacrilege!
Cheers -