I wrote my own program that computes moon phase, sun & moon rise/set times, draws it all on the image and exports it as a new jpg... It's lacking a little functionality right now, and it's Mac only, but eventually when I have time to iron some things out, I'll release it as freeware.
If there are any
Mac users (10.4 or higher) here with homebrew cams that want to beta test it, send me a PM. No guarantees

