Satoshi T
Imaging sensor of camera make less noise under the environment of the lower temperature. It's not a problem now of Australia. :) as another point, when you use camera at high ISO and long exposure in the dark, discrepancy of the imaging element will be actualized. Inconspicuous in normal shooting, it looks to enlarge the difference between the elements. They are "noise". "Noise reduction" feature to suppress this in camera function. but cameras which commonly sold, because they are not optimized for long exposure, not the level of noise reduction satisfactory in astronomical photography.
Attitude of noise of each sensors is nearly constant. As a way to take this point, I have heard the following method.
1) Put a cap on the lens, the same ISO and the same time the shutter as was actually astronomical photography, "to shoot only the noise."
2) To negative the shot of noise in the post-process.
3) to synthesize "negative noise" with astronomical photography.
4) only noise components is canceled. Since I'm not a specialist of astronomical photography, the method are general theory. To hear the story of the actual experience may try to ask questions in "Talk" in Tookapic :)
Elena wow! Satoshi, thanks a lot for your comment!
Satoshi T Clear sky. I can see KIWI in the middle of under half :)