There really aren't any jobs in astronomy if you don't have a PhD in the field - you need one to teach college or do research, or both, and that's what most astronomers do. With a bachelors, you could teach high school (in most states) or maybe work as a research assistant somewhere - if you want to do astronomy - or maybe at a museum - but there aren't many of these jobs. With a masters, you could do all that and teach community college.
If you want to be an astronomer, you'll need to go to grad school, and if you're planning to go to grad school in astronomy you should be majoring in physics, not astronomy - astronomy as a major doesn't require as much physics as you need to get through grad school in astronomy.
