Quote Originally Posted by ahab1372 View Post
I'm by no means an expert, but IIRC you want to shoot at low ISO. Long exposure already adds noise, you dont want to add high ISO noise.
Actually, noise is not that dependent on ISO. Most of your noise will be photon noise and this is totally independent of ISO. And as IIRC, read noise actually tends to be lower at high ISO. Thermal noise- which will be a factor unless you use long exposure NR- is (I think) not dependent on ISO.

The only reason not to use a high ISO is not to blow highlights. Taking shorter exposures and stacking helps avoid this also (more exposures gives more read noise... usually not a problem)