"It is sometimes hard to believe that tiny ice crystals floating in the air or clouds can make such precise and beautiful sky geometry," comments Cowley. "Two reasons:- One, the small crystals unlike their larger and more familiar snowflake cousins are near optically perfect. Two, they are set firmly in near perfect alignments by aerodynamic drag forces as they drift slowly down relative to local air currents. Only the circular 22o halo comes from tumbling crystals and they generate geometric perfection, too!"
More optical perfection may be found in the space weather photo gallery. www.spaceweather.com