What makes an astronomer a professional, and what makes them an amateur?
It used to be simple; a professional has a degree, and is paid to do it, while an amateur doesn't, and isn't. But that's way too simplistic these days. Many people who are technically amateurs have equipment that is absolutely killer, know their stuff more than many pros, and do real science.
Fraser Cain from UniverseToday.com has written an online feature for Wired Magazine showing some of these amateurs and their equipment. I see a lot of familiar names and a few familiar faces there too; these guys take images that you would not only be proud to hang on your wall, but some folks would pay good money for the chance. Check out the images in the article; I bet more than one will wind up as someone's background.