Is it permissible to take a picture of the sun setting?
According to some there is indeed a prohibition to take a picture of the sun. Even according to those that are lenient, it seems that printing such a picture would be prohibited.
There is room for leniency if it is not of the full sun such as when it has partially sunken or it is partially blocked by some clouds.
See also here:
ראה מנחת יצחק ח”י, עב. אבל ראה שו”ת שבט הלוי ח”ז, סי’ קלז ה-ו.
נקודת הכסף קמא, יג. ובשו”ת שבט הלוי אות ז שם.