If you look up at the moon yesterday you may

have seen a ring around the moon.

Image result for halo around the moon

Rings around the Moon are caused when moonlight passes through thin clouds of ice crystals high in Earth’s atmosphere. As moonlight passes through the ice crystals, it is bent in a way similar to light passing through a lens. The shape of the ice crystals causes the moonlight to be focused into a ring.

http://coolcosmos.ipac.caltech.edu/ask/172-What-causes-a-ring-around-the-Moon-