But consider this... If you take
too fast of a shot of the stars, you might get a 1 pixel spec, one dot. Whether you use in camera JPG conversion or RAW->JPG conversion, the conversion algorithm is likely to mistake that speck for noise and erase it.
Actually, not "likely to", it
will erase it! It you take an exposure of several seconds, you'll get at least a slight 'smear' of more than one pixels. that will enable you to turn-up the noise reduction to completely erase spurious noise, while keeping even the slightest hint of a star trail to remain.
It works. See post #9 above. Tho I wish that was a 10 second instead of 30 second exposure.