Cees BassaHappy new year! Another year means another year-long keogram! Every 15 seconds throughout 2022, my trusty all-sky camera took a picture of the sky above the Netherlands. Combining these 2.1 million images into a year-long keogram reveals this picture, which shows the length of the night change throughout the year (the hourglass shape), when the Moon was visible at night (diagonal bands), and the Sun higher in the sky during summer, as well as lots and lots of clouds passing overhead.
Nichol Brummer@cgbassa beauty! Strange, why are sun rise/set blue and not red?
@Nichol It's related to the exposure and gain control of the camera, which changes drastically during twilight -- from a few milliseconds during daytime to 15 seconds during night time. The transition between blue and black colors is about an hour after sunset and an hour before sunrise. If you zoom in on the keogram, you'll see red/pinkish colors around those times.
@cgbassa and of course, our eyes do the same kind of thing around twilight, and this also affects our colour perception. But at least the red and blue are explained by Rayleigh scattering.. and the opposite horizon becomes more violet.