you can have 1 star base per gravity well with the possible exception of (and feel free to prove me wrong) 4 star bases in a Stars gravity well.
the star base constructor ship counts against your fleet cap, but once its actually building a star base you can count it as being destroyed so you get that population back.
p.s to anyone claiming this thread is necro'd and whining about it. Buzz off was just answering the question.
