Several friends and I have a great yet unexplored interest in Astrophysics, and interesting Math not taught in the typical high school course. We have decided on forming a discussion based "club" (we will read/do research in between discussions) to help us learn more deeply and efficiently. I am a senior in High School, and would love to accomplish something by the summer because it may be difficult to continue discussing the concepts with the same people afterwards. We would like to try and tackle some relativity, but our math background in limited (I'll be starting multi-variable calculus next semester, and there are a few that haven't taken calculus yet). I was wondering if anyone has any suggestions or directions for study that may be satisfying, yet plausible. We could find help for some difficult concepts, but we can't have a Physics professor with us all the time.