Get Almanac's Daily Updates Extended Forecasts Where to Buy Contact Us

Moon Dogs

Photo Credit
Matin Turner

The False Moon Phenomenon

Written By: Bob Berman Astronomer

When the Moon is low in the sky, a bright “false Moon” (a well-defined saucer of brilliant moonlight) may hover off to its side. This is known as a Moon dog!

What is a Moon Dog?

Sometimes, these “saucers” are distinct bright spots attached to a halo around the Moon at a point 22° to its right or left—or both sides at once. Often, however, they may seem to appear without the halo.

By day, with the Sun, one of these phenomena is called a parhelion, or sun dog. By night, it is called a paraselene, or Moon dog.

Read Next

Look for a Moon dog when you see high, thin cirrus clouds near the Moon.

moon dog over the horizon
Photo of Moon Dog
Photo of Sun Dog by Donna Winsted
Moon
About The Author
Bob Berman

Bob Berman

Astronomer

Bob Berman is an astronomer, author, and science communicator with decades of experience making the wonders of the universe accessible and engaging. Known for his wit and insight, Bob has captivated a...
Read More from Bob Berman

More Like This

Comments

<span>Ddiamond</span> Tue, 03/02/2010 - 19:07
Altho I am old and I have lived in northern Illinois most of my life, I have only heard of SUN dogs. Also, I was told as a youngster that there is weather folklore around sun dogs, i.e., a change in the weather. Do YOU have a comment? Thank you... Dean
<a title="View user profile." href="/author/editors">The Editors</a> Wed, 09/29/2010 - 11:58

Hi, Dean, Yes...Sun dogs, also called mock Suns or parhelia, look like second Suns in the sky, appearing at the same height of the Sun and to its right and/or left by 22 degrees or more. They are caused by light that is refracted through ice crystals in the atmosphere (as through a prism) and exhibit the colors of the rainbow.