Like darkcoder said, maybe instead of using light sources for the stars, use shaders to create light-emmissive objects in their place.
I think there's a limit on how many emmissive objects you can have, and, again, I'm not sure how many this is, or even if it's the same amount as GDK lights, but experimenting might not be a bad idea.
As to adapting the lights to some hide or turn off when they're not in the viewable screen area, I feel might be a bit long-winded to code...
--------------
So Endeth What Was Begotten From That Moste Darkest and Forgotten Of Times...