As far as I know, constellations haven't really been talked about. There's an undeveloped Astronomy skill and that's about it.
The only place I know of where other planets are talked about is in terms of
Summoning, but summoners access other planets via magic, in such a way that leads me to think they don't really care where the planet is in the sky...
This sounds like the sort of thing you could look into developing in the World Development forum, if you are interested