Do yourself a favour and drop it back to ISO800 and go for longer exposures. You will find it much easier in the long run than trying to beat the noise from the ISO1600. It gets really hard to process out at that ISO unless you have lots and lots of images to stack.
To get you best images my suggestion would be ISO400 to 800, get plenty of exposure time (up until white out
) and take lots of them. Try 20 or 30/ 2min exposures at ISO 800 and see how you go
