Lunar Halo and Jupiter

April 02, 2004

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Provided by: Philippe Moussette
Summary authors & editors: Jim Foster; Philippe Moussette

The above photo showing a lovely lunar halo was taken early last month (March 5) from Cap-Rouge, Québec, Canada. Jupiter is just inside the halo, to the left of the Moon. Though Jupiter is one of the brightest objects we can see in the night sky (magnitude of about -2), it pales in comparison to the full Moon (magnitude of -13). Halos result when sunlight, or in this case moonlight, enters hexagonal ice crystals in cirrus clouds. Refraction of the moonlight in randomly oriented ice crystals produces a ring or halo around the Moon. The halo pictured is a classic 22 degree halo (22 degrees angular distance between the Moon and the actual halo -- a little more than two fist widths when held at arm's length). In order for a halo to appear, the Moon (or Sun) must be at least 22 degrees above the horizon.

Photo details: Canon digital (Rebel) camera, fisheye lens, 1600 ASA, exposed 5 seconds

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