What field of astronomy has the least math involved?

Sounds like you're most interested in planetary astronomy. Keep in mind that any field of astronomy will require a PhD to do research in that field, and most astronomy PhD programs require that you take the Physics subject GRE to apply, which in turn pretty much requires a physics major to p. And that's going to be a lot of math no matter what you want to study in the end. All the stuff you listed is in fact math-intensive to study, some parts more than others.