Returning to the question of the D70, I looked at some IR images in the archive base and saw they all were taken with unmodified camera .... Shutter speeds were long, but not excessive, typically around 1/8 to 2 sec. Some times even shorter, at ISO 400 or so. I shot many of them with a hand-held D70.
Here is an exampe, under very dull and rainy clouds. EXIF says f/7.1 with a¨Nikkor 105, 1 sec, ISO 200. Thus likely done from a tripod.