When it is cold, the clouds present at an altitude of about 6000 meters load up with small ice crystals. The light of the moon (or the Sun) then comes through its clouds and meets the crystals, which will refract the light rays. What creates the lunar halo.
Last night, did you see the moon adorn itself with a lunar halo? ? It is an optical phenomenon, called “paraselene” (from the Greek, next to the moon). This ring of light is caused by ice crystals in the clouds, which reflect the light of the moon?#Brittany pic.twitter.com/Rfa4tbPDFZ
– Morlaix Science Center (@EDS_Morlaix) January 24, 2021
Depending on the conditions, the phenomenon will therefore appear more or less intense. In any case, it gives the impression that the sky inside the light ring is darker than the rest. This is again an optical effect, caused by the angle of refraction (the light beams cannot be refracted at less than 22 °) and the place of observation.
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This lunar halo is very well known and is not that rare. In any case, it intrigued our readers, who sent us photos. Feel free to send us yours too!