In reply to The Lemming:
The tools I use for astrophotography are all free and are...
Astrophotographytool (APT) - for collecting subs, controlling the camera, making sure focus is spot on etc
Deepskystacker (DSS) - for checking each sub, registering and stacking
GIMP - free version of photoshop - probably not as functional but it's good enough for me.
If you're simply shooting a load of photos manually then shoot in RAW and you can dispense with APT (or equivalent). Do try to collect a load of dark frames at the same temp, ISO and exposure time as your light frames. they'll make all the difference.