I was looking at the web site of Andy's friend in London, and saw an interesting tip.

To remove the noise from long, digital exposures, or shots made at high ISO, try shooting the same scene multiple times (on a tripod, of course) and then stacking and averaging the shots. His point is that because noise is random, it won't be in the same place in each shot. And that if you stack enough shots (his example has 5 layers) the noise will be averaged out of the shot.

It's at the bottom of this web page.

Some obvious conditions apply: the shot must be static, and all images must be exact duplicates. So a tripod is mandatory. I assume that by "averaging" he means simply stacking the shots in Photoshop, which will itself average them out.

Worth a try, especially since this fancy dSLR I have makes unbelievable noise in long exposures.

I think I've posted this link before, but here's another benefit of stacking. Don't miss the gallery page for some cool star trails.

Z-Z, it appears that merely stacking the photos is different to 'averaging' them. Is Photoshop able to 'average' the pile of shots?