James Wiseman mentioned that this is the place to discuss quirks of digital cameras and I’ve noticed one. I haven’t had much luck with long exposure photography using my S2. By long exposure I’m talking about 30 to 180 minutes or so (star trails, etc) at f5.8 to 8 with ISO set to 100. Has anyone tried with a higher ISO? Would it matter or is this a limitation of using a CCD chip instead of film? So far my results show only the very obvious stars and have a lot of noise (pixels of RGB colors where it should be dark).

They have a great article about capturing star trails with a digital SLR in the March issue of Sky and Telescope Magazine.

"Astro Imaging – Capturing Star Trails with a Digital Camera
By Peter Michaud | March 2004, p. 126-131"

It is a very good article and their technique should work well for other subjects as well.

There is an article on their website explaining the noise in long digital exposures:
http://skyandtelescope.com/howto/imaging/a...ticle_953_2.asp

Good luck.
/Stefan

Hi James,

You can't take pictures that long with a CCD camera, the thermal signal will fill the well capacity of every pixel. I even doubt that you can take one that long with an astro camera cooled with a thermo electric cooler.

What you can do is take a shorter picture followed by a picture of the same time with the lens covered (that's called a dark frame) and substract it from the first one. You can repeat this many times and add the results.

I let you know if I can find a program that can do that.