Where can I find details about the constellations and night sky characteristics of Toril? Is this information presented in any of the released books?
There's nothing published that I'm aware of. I have a reasonably good knowledge of the Forgotten Realms material presented in Living Forgotten Realms modules, and I don't know of any night sky material there, either.
Candlekeep has an unofficial article about the subject, which is based on official material. There is also a comprehensive discussion thread here, with links to a few visual resources and much discussion of Selune.