I've spent the weekend using my hired 5D Mk3 as much as I could, which wasn't lots but was a reasonable variety of tasks.
Astrophotography... here's a 2 minute 3200 ISO CR2 and JPG:
http://www.astrophotography.com.au/u...3/0C7A8086.CR2
http://www.astrophotography.com.au/u...3/0C7A8086.JPG
The JPG is batched out of DPP without any adjustments other than to set to daylight WB. So there is noise reduction applied as per defaults of the camera.
I did use ICNR. I was looking to compare to what I normally do with the 7D and as such used settings like ICNR.
It was a cool night, approx 13 degrees C. So noise will have been not at its worst by a long shot.
The location was from my patio so reasonably light polluted.
Roger.