Crepuscular Rays and Iridescent Clouds

May 17, 2019


Photographer: Piero Armando 
Summary Authors: Piero Armando; Jim Foster

This alluring mixture of crepuscular rays and iridescent clouds appeared just after sunset near Turin, Italy, on March 15, 2019. Crepuscular rays take shape usually when the atmosphere is dusty or filled with aerosols and sunlight streams through gaps in distant mountains or through gaps in clouds, often the turrets of cumulo-form clouds. In this case, the rays spread over the mountain range that blocks the clouds that form them. The rays seem to converge toward the Sun because of the viewer's perspective.

Iridescent clouds, a diffraction phenomenon, are caused by the interaction of sunlight with the minute droplets composing mid-altitude clouds. The resulting pastel greens, pinks and purples are indicative of overlapping color orders resulting from wave interference. Note that the silhouetted mountains in the background form the Orsiera-Rocciavrè range. The highest peak here reaches 9,480 ft (2,890 m). 

Photo Details: Canon EOS 600D camera; 1/1250 second exposure; f/8; ISO 200; focal length 70 mm.