Usually I do walk in evenings at 7 to 7:30 when I got free time. Ten days back I was walking on our terrace, my dad too is sitting on opposite side. His thought process is like to know about everything that is going on around us. While walking I stopped and start observing halo ring around moon. I came to know my father is observing me and started walking, I am avoiding his eye contact because for sure he will ask what is that and I was like very tied too tied because of my work and not at all interested in to know about it. He was like we should know what is happening around us and there will be reason for everything and we should know about it. But I was not in that mood actually. My dad called and asked to sit in front of him. He started saying that in our days of schooling to clear a doubt we use to suffer a lot, we use to refer a lot of books in order to clear our doubts. But its not like that in your situation actually, you can clear your doubts in couple of seconds if you want to know. He just told me, may be you are engaged with lot of works but don't be that lazy to explore little things around you. And after a long session with my dad I started googling about that halo ring around moon.
It is known as 22 degree halo ring. If that ring is around moon known as moon halo ring, if that ring is around the sun known to be sun halo ring. That halo ring is because of refraction/reflection of light due to sun or moon on the hexagonal ice crystals which are on clouds. This is what makes a halo ring around sun/moon with 22 degree diameter and this is the reason behind why it is known to be 22 degree halo ring. Mostly these halos are bright white rings but sometimes the dispersion of light as it passes through ice crystals found in upper level of thin and wispy clouds can cause a halo to have color.
It is formed when light from the sun or moon is refracted by ice crystals associated with thin clouds. Light undergoes two refractions as it goes through an ice crystal. And thus passed light ray undergoes to certain amount of bending which is depends upon the diameter of ice crystal.
When a light ray enters one side of columnar ice crystal and comes out through another side. Light is refracted when it enters the ice crystal and once again when it leaves the ice crystal. So these two reflections makes light to bend to 22 degree from its original direction and this is what produces a ring of light observed at 22 degrees from the sun or moon.
