THE SOUTHWORTH PLANETARIUM
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Altitude: 10 feet below sea level
Founded January 1970
Julian Date: 245919.16
2019-2020: CXIII
"We love the Universe. It's Great!"
THE DAILY ASTRONOMER
Tuesday, March 10, 2020
The Fetching Moon Dogs
Moon dogs!
Mock moons!
Or, to the incurably pedantic, paraselene.
In case you weren't outside admiring the night sky, these phantom canines
materialized out of the firmament last night. They appeared similar to
the image below:
[image: Moon_dogs.jpg]
*Moon dogs photographed in the sky of Edmonton, Albert*a
Moon dogs are those ghostly moon images appearing at either side of the
actual moon. They only appear when the moon is particularly bright and
shining through a cirrus or cirrostratus clouds. The moon dogs occur by
the refraction of moonlight through hexagonal ice crystals suspended within
and around the clouds. They resemble spherical splotches within the 22
degree halo that often encircles the moon.
Sun dogs occur by the same process, but are much easier to find because the
Sun is substantially brighter than the moon. In fact, the moon has to be
larger than a quarter to produce moon dogs. Also, unlike Sun dogs, moon
dogs hardly ever exhibit any discernible colors due to their low light
levels. Our eyes are not capable of distinguishing colors at low light
levels.
Technically, moon and sun dogs are meteorological, not astronomical events.
However, moon dogs, like meteors and the aurora borealis, are produced by
the interaction between a cosmic entity and the atmosphere. the Were our
planet devoid of an atmosphere, we'd never see them. Well, of course, we
wouldn't even be here in the first place.
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