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(meteorobs) Re: meteorobs-digest V3 #239
In a message dated 12/17/1999 6:57:44 AM Eastern Standard Time,
owner-meteorobs-digest@jovian.com writes:
<< Date: Fri, 17 Dec 1999 01:49:49 EST
From: Rowan1955@aol.com
Subject: Re: Coma Berenicids (was Re: (meteorobs) Okay Lew)
I want to know what a "Moondog" is just in case one arises over the maples
or
great pumpkin patch >>
High, thin cirrus clouds are made of ice crystals, even in the Summertime.
Sun or even Moon light reflects from these hexagonal crystals creating halos,
pillars and spots called Sundogs or Moondogs. Also known as Parhelia (for
the Sun) and Parselenes (for the Moon). In the daytime, when there is
cirrus, cover the Sun with your hand and look for a faint primary halo, 22
degrees around the Sun. The Sundogs look like bright spots or more often
multi-colored parts of a rainbow. To take a picture get your camera in the
shadow of a pole and take a meter reading of the sky brightness, then open
the stop two stops for a nice rendition of the color.
For the Moon, cover the Moon with your hand and you will often see a halo if
cirrus is present, sometimes the Moondogs. A great book on these things is
Minneart's, Light and Color in the Open Air. Get it through interlibrary
loan.
Clear skies,
Bob Young
State Museum of Pennsylvania Planetarium
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