Certain Phenomena only work outside, some only work inside, and some don't care.
"Inside/Outside" isn't really the dichotomy. The main dichotomy is the 3 "Superior Conjunctions" which are "Day," "Night," and "Sheltered" (which is essentially "inside.")
There are Phenomena that turn day into night or sheltered into day or night and similar so you're not utterly cut off from a given phenomenon based on where and when you are.
It does have a lot of different named features but they all fit together in a very elegant and user friendly way if you're ok handling lots of words (and some of us, like me, count "lots of words" as a positive.)
As to how an Astronomer can do stuff inside, I think SirP could explain that better than I could. He's the Astrophysicist, after all.