Moondogs Above Ursel, Belgium

November 26, 2006


Provided by: Lode Verhelst
Summary author: Lode Verhelst

The photo above shows a pair of faint moondogs escorting the nearly full Moon through the night sky over Ursel, Belgium. During the daylight hours, cirrus clouds streaked the sky, and sundogs were visible much of the afternoon. When the Moon arose, I noticed these moondogs or mock moons. The atmospheric optics for this are of course the same as that which causes sundogs, however, because the Moon is so much dimmer than the Sun, moondogs aren't nearly as bright or colorful as their daytime counterparts. Both sundogs and moondogs reveal that the clouds are hosting horizontal plate ice crystals. These plates drift slowly downwards with their large faces almost horizontal. When moonlight passes through the crystal side faces, patches of pale light, on either or both sides of the Moon (approximately 22 degrees away from the Moon itself), may be observed. Photo taken on September 9, 2006.

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