I don't know if I'm qualified to answer this, but I'll try to help out. I wouldn't really say Celestia can do 'photorealistic' pictures, but it can give a quite accurate view of the sky from any point in space, whether it be from another solar system or on Earth. What I mean is, depending on your computer, the images can look kind of grainy and artificial, so I dont know how photorealistic you can get. There are a few ways to display the stars in Celestia, maybe if you look at those you might find what you are looking for. There are addons that add stars to the database, such as the 2 million star addon, which I can't remember where to find heh. The stars are all real and in the right spots and come from astronomy databases, so if you're looking for a realistic sky, this is a good program.
I'm sure you could add a custom database of stars to the program, but it might be easier to use the stars already in the database, as there are very many of them. I think there are something like 100 thousand in the basic Celestia download. There should be people here who know how to make a custom star database, so hopefully they can help. Hope this helped
