I downloaded a new video Podcast to try today - Photoshop for Digital Photographers.
It's worth a look if you want to learn your way around Photoshop, and maybe pick up some new processing techniques. It is aimed at general photography, not astro, but I'm sure some of the techniques can be applied no matter what sort of photo.
Being a video podcast it can be viewed on you PC with software like iTunes, or you can view on your iPod Video or equivalent video capable MP4 player. The video component shows the computer screen as the host describes the steps - very easy to follow!
Al.