Dave's already started a good job here by the look of it
so this seems as good a time to mention dark frames and the Nikon Noise Trick. The Nikon D70, which has serious noise problems (for astronomers anyway) above 200ISO, actually does some noise reduction even if you don't want it to, and with astro work, a small star could easily be misconstrued as noise.
If you set the D70 for, say, a 5 minute bulb exposure, with the noise reduction system OFF, BUT, then physically turn the whole camera OFF at 5 minutes, you will have a completely unmodified frame, no mistakenly removed stars....
The only other thing you have to do is take a "dark frame" for the same amount of time and subtract this from the original shot. Make a dark frame by taking the same time exposure, with the switch off method, but this time with the lens cap on. This, then, will only take a shot of the thermal noise. Take the thermal noise away from the original and bingo, a perfect no noise exposure.
Did that make sense ??