Um no. I was under the impression that it only affects files taken at ISO800 and above? I thought that ISO400 would be an easy way to avoid all of that.
Was I wrong?
I think the "above ISO 400" refers to High ISO noise reduction. Also on page 83 of the manual it talks about long exposure noise reduction and suggests you can turn it off. For the rest of this post please bear in mind that I have never used a D80 so I haven't been able to verify the suggestions.
Have a look at Christian Buil's (author of IRIS) page here
where he states "Digital SLR Nikon D70,D80, D200 reduces the noise by filtering the image with digital processing for an exposure length above 1 second. The issue is that the digital filter is also applied on the raw image, which prevent them to be used in rigorous astronomical application (faint stars are deleted as well as the noise !...)
All is not lost, however, as my post here
, which refers to another page on Chrisitan's site, suggests. "Mode 3" is easy to do and might be worth a try. Take another shot similar to the previous best effort in the normal way and then repeat the shot using Christian's "Mode 3".