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That breathtaking vision in the night sky is the result of ice crystals refracting the light of the moon. The halo rings the moon when high, thin cirrus clouds made up of millions of these crystals cover the sky. The moon's light enters into the hexagonal-shaped ice structures and is bent before passing out another side of the crystals, causing a ring of light to appear around the moon. But this phenomenon is not limited to the moon -- given the right conditions, you can spot a sun
halo as well. Halos typically appear as a ring of white light around the moon or the sun, but they can also appear in color patterns. The most common type of halo is the 22-degree halo, so-called because the ice crystals refract the light of the moon or sun at an angle of 22 degrees. A less-common type of halo is the 46-degree variety, which has a larger diameter than the 22-degree but is also fainter. According to folklore, a moon halo indicates that bad weather is on the way. There may be some truth to this since the halo is usually caused by high-altitude cirrus clouds that precede a warm
front and an associated storm. One dark, cloudy night, you might also be lucky enough to catch a glimpse of another spectacular moon show -- the lunar corona, when the moonlight is diffracted into hazy colored rings.
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