In article , username wrote:
[...]
I have a phd in math, but I am not a science professional (left university
after I got my phd, now I work for a large bank). I enjoy my current work
very much, but I never lost my interest in science (in fact, I published an
article on chromosome structures, together with my twin brother, in
"Science" last year).

Ooh -- congratulations! Could you reveal your name (or your brother's)
so we can look them up?

I enjoy astronomy as a hobby as it is abstract and so close to real science.

That's funny -- someone in another thread was calling astronomy abstract too.
It seems awfully concrete to me. But I like it very much, as an observer
an an amateur physicist.

My question: are amateur astronomers actually contributing to science
(besides shooting nice images!), and if so, how? Perhaps a FAQ, but I am
interested, as I know from experience, that my hobbies tend to get pretty
serious over time :-)

One thing I enjoy is observing asteroid (and occasionally lunar)
occultations. It's not necessarily demanding in terms of equipment --
a modest telescope, a WWV shortwave receiver for time signals, and
a tape recorder, is enough for visual work. More ambitious observers
get a sensitive video camera and a portable video deck (often a camcorder).

With reasonable numbers of observers sprinkled along a shadow path,
they can measure accurate sizes and shapes of asteroids, and can hope to
detect asteroidal satellites. If you're mobile you can observe lots of these,
and even non-mobile observers like me can usefully try for one every
few months. I've tried for seven or eight and actually seen two
asteroidal occultations, plus a couple of spectacular lunar grazes.

Stuart Levy