Education-related question for any astronomers

So this feels like a dumb question but surprisingly I haven't been able to find much information. I'm a junior in college working on a biology degree. I'm too far along to switch majors now, but for the past year and a half I've been more and more interested in astronomy. I'm wondering what the usual requirements are for entering an astronomy master's program, and if it's even realistic to go from biology to that. I live in Oregon and would want to stay on the west coast. Any relevant info? Thanks.

go to Berkley and take some courses from Perlmutter and Filipenko