About Canon 500D noise

DPreview.com is one of those sites that do an amazing job of dissecting cameras down to a level which can become useful for astrophoto.

For example their measure of noise levels for the 500D is something I think might be useful to estimate the optimal ISO / # pics required for deep sky imaging and stacking.

ISO Std Dev

100 3

200 4

400 5.8

800 8.3

1600 11.3

3200 15.8

6400 24

12800 35.7

However, if you have a clue on how to do it, drop me a line