I was reminded of this by something I wrote in another thread.
There is nothing in the BAUT rules about the ownership of copyright or other IP in messages posted on this forum. I would assume copyright should be assigned to the forum so that posters cannot complain about having their posts edited/deleted (or even not deleted) by the moderators.
There is no clear case law for this (in any jursidictions I am aware of) and if there were a particularly argumentative/litigious member, they could exploit this to cause problems.
You might need some wording to ensure it is only the copy posted on the forum that becomes the property of BAUT; in particular to allow the posters in the astrophotography forum to maintain ownership of their work.
And then, I don't know if BAUT is a legal entity that is allowed to own copyright...
I should add: IANAL (but have been responsible for IPR in the past).