While stargazing, have you ever noticed a large circular band of light surrounding the moon? If so, you have seen a lunar halo.
A lunar halo is caused by the refraction, reflection, and dispersion of light through ice particles suspended within thin, wispy, high altitude cirrus or cirrostratus clouds. As light passes through these hexagon-shaped ice crystals, it is bent at a 22 degree angle, creating a halo 22 degrees in radius (or 44 degrees in diameter). A double halo, sometimes with spokes, may be seen on rare occasions when light reflects off water or ice.
source
we have a lunar halo tonight. it's amazing. the sky is beautiful and clear, and you can clearly see stars in this picture. as well as the tree in my front yard.