Cees BassaJan 4, 2025
For the 4th year in a row, my all-sky camera has been taking an image of the sky above the Netherlands every 15 seconds. Combining these images reveal the length of the night changing throughout the year, the passage of clouds and the motion of the Moon and the Sun through the sky. #astrophotography
Show threadCees BassaJan 4, 2025
To clarify what is exactly happening, this figure compares the keogram with predictions for rise and set times of the Sun and the Moon.
Show threadpandora
@cgbassa why do the red areas/curves have such a kink in them?
Jan 5, 2025 at 11:06amWeb
Show threadCees BassaJan 5, 2025
@pandora This is due to the location of the Moon in its orbit along the ecliptic. In winter, the full Moon will be up for longest because the full Moon is happening at the highest point in the sky. That means that the days before or the days after the Moon will be lower in the sky at culmination, leading to it being above the horizon for less. During summer this is reversed. At full Moon the Moon is lowest in the sky and hence up for shortest. In the days before or after it stays above the horizon for longer, which leads to these kinks. I hope that makes sense.