I don't know what these people were studying exactly, but... there are many misunderstandings in our religion. There's big difference between believing in something as in existence and relying, trusting, worshiping and/or practicing. The example for this is magic. We all know that magic is over there. Allah told us that in Quran. But, we don't believe in it in sense of not relying, using, practicing it, etc.
As for astrology. It's part of unseen and forbidden. We are not exactly told much about it, but it's explained that we should stay away from it. Just like from the magic. Astral projection is real, too, but we're not considered to practice that.