Time-lapse photography of clouds and other phenomena in the sky

See also a static photo from the beginning of the timelapse and MTG-I1 (Meteosat Third Generation), Meteosat-12 satellite loops RGB VIS-IR, and RGB Cloud Type (CHMI version) image products. The area was somewhat covered by dust, as can be seen in the ALC profile from nearby Ústí nad Orlicí. The two black vertical lines indicate time span of the timelapse.

Satellite tracks through the night sky.  While some thirty years ago, when I was active in astrophotography, satellite passes through the night sky were rather a rarity that all of us got excited about, today satellites pose a serious problem for wide-angle astrophotography, especially when timelapsing the night sky. Satellites can be removed from a static photo by various methods, but for timelapses this would already be a challenging problem. Fortunately, the Earth itself helps here (to a certain degree) - when satellites enter its shadow, they are no longer visible.

This can be clearly seen in the timelapse above: the satellites flying from the right side of the frame (west) do not reach the left side, southeast part of the image. The same is true for satellites flying in polar orbits (from south to north or vice versa), they only appear or disappear at some distance from the left edge of the frame. Moreover, it is possible to notice how this whole “satellite darkness area” slowly drifts westwards (to the right, towards the center of the frame). This is nothing else than the Earth's shadow - when the satellite enters it, it ceases to be visible (and vice versa). The only trails that make it all the way to the left edge are planes - they usually also have dotted tracks (a result of blinking of their position lights). All of this is nicely visible on both the classic (“normal”) timelapse and the “startrails” version (from about a third of the timelapse onward). See also this static image of startrails, in which the satellite (and aircraft) tracks are shown at their full length. The short gaps in the satellite trails are gaps between the timelapse frames. Another thing to notice is that the satellites do not disappear at any precise location - this is due to the fact that they fly at different altitudes, and the position of the Earth's shadow depends on its height above the surface. Satellites on the lowest orbits disappear most quickly after the sunset, while the higher ones disappear later (if at all).

The last thing that makes this timelapse interesting is the blue color of some of the satellites. In the entire timelapse (just under one hour) I found about seven of them in the images. These might be the newer generation Starlinks, coated with a special coating to reduce their reflectivity (see e.g. info here). Though, I don't know for sure.