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Moonbow
From Wikipedia, the free encyclopedia
A moonbow (also known as a lunar rainbow or white rainbow) is a rainbow that occurs at night. Moonbows are relatively faint, due to the smaller amount of light from the Moon. As with rainbows, they are always in the opposite part of the sky from the moon.
It is difficult to discern colours in a moonbow because the light is usually too faint to excite the cone colour receptors in our eyes. However, the colours appear in long exposure photographs.
A coloured circle around the moon is not a moonbow—it is usually a 22° halo produced by refraction through hexagonal ice crystals in cirrus cloud. Coloured rings close to the moon are a corona, a diffraction phenomenon produced by very small water droplets or ice crystals in clouds.
Moonbows are most easily viewed during full moon (when the moon is brightest), just after astronomical twilight in the evening or before astronomical twilight in the morning (when the moon is low, not overhead).
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Few places in the world frequently feature this phenomenon. Cumberland Falls[1], near Corbin, Kentucky, U.S.A.; Waimea, Hawaii; and Victoria Falls on the border between Zambia and Zimbabwe are widely known for moonbow occurrence.
Moonbows are commonly reported in Yosemite National Park in the United States as a result of the numerous waterfalls in the area.
- ^ Bailey, Bill (1995). "Cumberland Falls State Resort Park", Kentucky State Parks. Saginaw, Michigan: Glovebox Guidebooks of America. ISBN 1881139131.