A moon dog, moondog, or mock moon,[1] (scientific name paraselene,[1] plural paraselenae, meaning "beside the moon") is a relatively rare bright circular spot on a lunar halo caused by the refraction of moonlight by hexagonal-plate-shaped ice crystals in cirrus or cirrostratus clouds.[2]
A pair of moon dogs over Didcot, England
Moon dogs appear as part of the 22° halo, roughly 10 Moon diameters outside the Moon.[3] They are exactly analogous to sun dogs, but are rarer because the Moon must be bright, about quarter moon or more, for the moon dogs to be observed. Moon dogs show little color to the unaided human eye because their light is not bright enough to activate the cone cells.
See also
Sun dogs
Halo (optical phenomenon)
22° halo
Moon ring
References
"Definition of paraselene". Collins English Dictionary.
Lisle, Jason. The Stargazer's Guide to the Night Sky. p. 83.
Lisle, Jason. The Stargazer's Guide to the Night Sky. p. 83.
Hellenica World - Scientific Library
Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License
