... A Sun Halo Over Cambodia . ... Credit: Nagy Attila Explanation: Have you ever seen a halo around the Sun? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. ... Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees , which corresponds to the radius of the Sun halo . A similar Moon halo may be visible during the night. ...