Is there anything in canon that states that star systems don't move? I mean, really, trying to put real world reasoning into a show that allows sublight flights between "nearby" stars to be done in a few hours or days is really silly. So maybe the star systems just move as the plot (and the Force) requires. This means astrogation is part science and part prognostication (and astrogators are probably good gamblers)...which is why there's a Force-based spec about it already. Oh...and the Chiss do it that way too. And then in Star Wars the fools turned from living navigators to droids and computers because they are the anti-Dune, and...
I really shouldn't post after a night of insomnia...