There are several forums around that are devoted to astrophotography. It would seem a natural for a a stack exchange on this subject.
Astrophotography is on-topic at Photography.SE, where they have a tag with over a hundred questions in it: [astrophotography]. In fact, a number of astrophotography questions were migrated there after the first beta of Astronomy.SE failed.
It's possible that there may still be a need for a more specialized astrophotography site, but it looks like that community's needs (at least for now) are being met by the tag on Photography.SE.