"The parasalene"
Illustration of a Moon dog (1890)
Public DomainIllustration of a Moon dog (1890) - Credit: Wikimedia Commons

A parasalene is the scientific term for a lunar phenomenon commonly known as a moon dog. This is a relatively rare bright circular spot on a lunar halo, which shows little colour to the unaided eye because its light is not bright enough to activate the cone cells of humans' eyes.


Moon dog
Creative Commons AttributionMoon dog - Credit: Karl Frankowski