Sometimes a diffuse white ring can be seen going all around the sky at
the same altitude as the sun. In the upper case the sun was high in the noon
sky giving a quite small parhelic circle with a radius of about 26 degrees
around the zenith. The sun is hidden by the medieval church tower of San
Negrentino in Switzerland.
The formation of this halo phenomenon takes place due to vertical
aligned ice crystal surfaces in high Cirrus clouds.
