MOON HALO ALERT

MOON HALO ALERT: It's cold outside. The Moon is waxing full. There's ice in the air. Add them all together and you have perfect conditions for a ring around the Moon:
Click on image to enlarge
Photo details: Canon EOS 5D, 8mm fisheye lens, ISO 200, 10s
"I happened to take a stroll outside last night," says photographer David Harvey of Tucson, Arizona. "The Moon was nearly overhead and surrounded by this eye-catching 22o halo."

Such haloes are formed when moonlight passes through pencil-shaped ice crystals floating in high freezing clouds. When you see a 22o moon halo, be alert for moondogs and moon pillars, too. They are formed by plate-shaped ice crystals that often accompany their pencil-shaped cousins.

The Moon is full on Dec. 31st. Mark your calendar for haloes.

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