A Sun 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° angle, creating a circular halo around the Sun.
The prism effect of light passing through these six-sided ice crystals also separates the light into its various color frequencies, making the halo look like a very pale rainbow, with red on the inside and blue on the outside.
Canon 6D Mark II
16-35mm f 2.8 canon L
3 shot HDR f16 iso 400 16mm