I have been doing astrophotography for several years but do not consider myself an expert. I would make a guess/stab at the fact that these are done by the standard timelapse techniques when involve tripod, adjustable camera like a DSLR, intervalometer set at 15-30 seconds and ISO of 1200 or more, and 2-3 hours of standing outside in the cold trying to keep warm. Then processing the series of shots in a timelapse software program like LR Timlapse 4 or 5 which renders allows "development" or color grading, and other adjustments and then it is rendered by the same software into a video. Once the video exists, it can be imported into your video editing program and adjusted for speed, exposure, color, etc.