There was an interesting exchange in comments to a recent BABlog entry dealing with the differences and relationship between amateur and professional astronomers. I suspect this discussion has longer legs than the blog comments are going to be read for, so I'm introducing the discussion here.

I'm a professional astronomer, employed at research and academic institutions for the last 25 years. I'm an IAU member (put those weapons away - I wasn't at Prague...) Plenty of research papers, a couple of books, some translations, public outreach publications... Used likewise lots of telescopes, spanning the energy range from the VLA to Chandra. So much for credentials.

I'm an amateur astronomer, going back to about age 10. I mowed yards for a summer while in junior high school to buy a secondhand 6-inch Criterion reflector, and still own 5- and 10-inch telescopes which get taken onto the back deck when I feel the need of a fix of firsthand photons (the deck we had extended for a better selection of sight lines between the trees). I started in astronomy drawn by the esthetic attraction of the Universe, and was somewhat puzzled to get to grad school and learn how many classmates were interested in astrophysics as a way to test physics on a grand scale. I kept thinking, "how can they possibly be very passionate about that?" My point is that I feel qualified to peek on both sides of the curtain.

Some of the blog comments seemed to respond to a much more pejorative connotation of "amateur" than I grew up hearing from professional astronomers. Of course, as a precise description of status, there is no particular reason it should be, except that certain things are much more likely to be done by one and the other - plus that special need to establish one's seriousness if writing a research report out of the blue... I will admit that, 20 years ago, I did use the term "armchair amateur" in a pejorative sense, to mean the folks who liked to flip idly through the latest issue of "Astronomy" and speculate wildly about cosmic matters. However, I have publicly withdrawn that connotation, in a world in which Eric Flesch in New Zealand beat a couple of professional teams to (at least public release of) a list of quasar candidates from careful cross-matching of optical, X-ray and radio catalogs; in which amateurs around the world have found hundreds of comets from quick examination of public SOHO images; and in which we see STScI and ESA proudly releasing HST images processed by members of the public.

I do see some real differences in the respective cultures:

A degree does suggest a certain completeness of preparation in the field at that time. This means one is less likely to be unaware of relevant issues (or at least need not constantly prove such an awareness). This fact reflects the extent to which the field is maturing - when a field is new, there are no such things as canned experts! This shows which areas of astronomy have been ripe for contributions by, for example, physicists following new instrumental opportunities. This was most effective when nobody else knew much background either (unlike, say, stellar spectroscopy, in which there is an enormous body of lore to master)..

Amateurs are not bound to productivity goals.They are free to follow what they find interesting or rewarding (and in fact I see no reason an amateur should do otherwise). If this is something with a low probability of payoff, or requiring a long-term time investment, no problem. For most professionals, if they want to put much of their time into something with a low likelihood of success, or in an area completely unsupported by funding institutions, that's a real problem. (Interested folks may see quite trenchant comments on astronomical funding in Rob Knop's blog Galactic Interactions).

Professionals may spend a great deal of time on nonastronomical tasks.Grant writing, academic advising, departmental committees collecting syllabus snippets for accreditation, financial reports, EPA audit paperwork on darkroom chemicals, writing documentation, all with deadlines caring not for one's research productivity. You don't do this kind of stuff without being paid for it.

Processing images for display is not something many professionals outside of EPO have any experience with (and it feels sort of odd after all those years of trying never to introduce artifacts in processing). One of these days I'll do the Palomar challenge, putting some 200-inch CCD mosaic data on an ftp site and inviting interested parties to make their best color image of them. All I first have to do is fight the mosaic stitching IRAF routines to make geometrically matching single frames from each filter... Just look at a typical week's APOD links to see the level many amateurs have reached. Professionals generally balk at buying Photoshop, although I'm told the GIMP is effective on their usual Linux platforms.

Amateurs have a huge range of expertise. Some are awesomely competent at running the telescope and imaging, but have very sketchy notions of the celestial layout behind them. Others can converse with professionals on their own terms, having become familiar with arcana of celestial mechanics and asteroid orbital perturbations.

Amateurs have taught the rest of us a great deal about automating everything from observations to remote operation to reduction. If it's not your "job", you don't have nearly as much patience with tedious grunt work (I seem to have too much).

Amateurs tend to be much pickier about their collimation and optical quality, probably because they use the same equipment more often than most professionals manage to use anything. Plus if it's their gizmo, nobody's hand get slapped for making an adjustment.

Amateur astronomy is foremost about a love of the sky. Research need not enter into it. However, many amateurs are interested in getting involved in research. Off the top of my head, I came up with a seriously long PowerPoint list of things that are within reach of a lot of amateurs.

Let the conversation ensue! But for me at the moment - it's a clear night, even if it's still 90 F outside. The stars are calling.