Lunar Halo

I saw one of these fabulous sightings last night above our house. Though the one I saw was very dim compared to the pictures I borrowed from google images. So no, the picture below is not my house. I have never heard of a lunar halo before and I find them most fascinating. So I shall tell you all about them.

Anatomy of a moon halo

The ring that appears around the moon arises from light passing through six-sided ice crystals high in the atmosphere. These ice crystals refract, or bend, light in the same manner that a camera lens bends light. The ring has a diameter of 22 degrees, and sometimes, if you are lucky, it is also possible to detect a second ring, 44 degrees in diameter. Thin high cirrus clouds lofting at 20,000 feet or more contain tiny ice crystals that originate from the freezing of super cooled water droplets. These crystals behave like jewels refracting and reflecting in different directions.

The shape of the ice crystals results in a focusing of the light into a ring. Since the ice crystals typically have the same shape, namely a hexagonal shape, the moon ring is almost always the same size. Also, they are sometimes called solar halos. Or if you want to be creative (like my brother and our friend Pete) you can call it a moonbow, a rainbow around the moon. They are pretty common and can be seen whenever cirro-stratus clouds are present at the convenient position and the skies are clear.