I am an undergraduate Physics major in my third year, and I'd like to concentrate in Astronomy or Astrophysics when I obtain my Masters and PhD. What kinds of physics classes should I take in preparation for this? I've already taken all explicitly-astronomy courses at my school. I was thinking Optics and Lasers, since they're crucial for communication and instrument design (e.g. for telescopes). But the scope has to be larger than that. What about quantum mechanics or photonics? Which disciplines of physics are most important? Thanks!