Moonlight can create interesting optical phenomena. The moon can be seen from the trees, a ring of light surrounds it: what are lunar arcs and halos?
The moon manages to create particular and curious optical phenomena. Moonbows form just like rainbows but are rarer. You must have water droplets in the air opposite the Moon. For example, the water droplets created by waterfalls are the perfect setup for creating a moonbow.
On the other hand, a lunar halo requires ice crystals, they must be short clouds, called cirrus clouds. Present at a height of 6 thousand meters. When they appear during the day they are extremely white. Ice crystals have a hexagonal shape. This feature is important: a faint ring of light 22 degrees away from the Moon. Under the right conditions, a second ring will appear at 44 degrees, but more often than not, it will just be the arcs of this second ring. A lunar halo has the function of announcing incoming bad weather.
Halos can also occur around the Sun or Moon, just like rainbows. In the case of solar halos , they offer more peculiar phenomena together with the 22 degree halo. A particular phenomenon are sundogs. These are two bright features to the left and right of the Sun on the halo. Visible anywhere in the world at any time, but can no longer be seen when the sun is low on the horizon.
- What Is A Moon Halo And How Is It Different To A Moonbow? (iflscience.com)