This is a composite of 900 pictures into one, which lasted exactly 15 minutes with a one-second exposure (times 900):
Short trails
ISO 1600, no noise reduction.
Update, from short after midnight:
Here’s another one, with only 90 pictures composed into one. But now each picture had an exposure time of 20 seconds at ISO 200, which actually took double the time – half an hour:
Star trails II
Thanks for viewing.