Also known as a Winter Halo, it is seen as a large ring of light all the way around around the moon at a substantial distance away from the center of the moon. Moon Rings usually appear in conjunction with a full moon. Caused by the refraction of the reflected sunlight, also called Moonlight, from ice crystals in the upper atmosphere. Because ice crystals have the same hexagonal shape the refraction almost always forms a large ring of the same size.
Photo : NSN - Taken in the front yard 12.25.12