I just got my new A810 working with CHDK and I thought I would try it out on the night sky. I was mighty impressed that I could get the results I got from a £50 unit.
Here is a portion of my first star shot showing Orion. It was created by stacking 10x 5s raw exposures recorded with the built-in Canon intervalometer. You can see a moving object as a line of 10 dots just above the 3 stars of Orion's belt. I am still investigating what it was.
My plan is to write a script that I can use to automatically record several hours worth of start shots. Hopefully, I should get some meteors, satellites and who knows what else.