Iridescent Clouds above Western New Jersey

March 12, 2011

Photographer: Lisa Gonnelli
Summary Author: Lisa Gonnelli; Jim Foster

The photo above shows a milky sky grated with iridescence. Iridescence clouds, also called irisation or opalescence, are in essence a detached corona. The metallic or pastel colors are caused by tiny cloud droplets (on occasion ice crystals) which deflects sunlight in such a way to generate overlapping colors. Therefore, the coloration is different from refracted sunlight, in the case of a rainbow for instance, and the overlap is minimal. Note that colors are purer and so more noticeable if the cloud droplets are similar in size throughout the cloud. Look for iridescence is mid level altocumulus or altostratus clouds, but always protect your eyes when observing near the Sun. Here, a cookie jar lid, just visible at the top of the frame, was used to block the bright Sun.

Photo details: Camera Maker: OLYMPUS IMAGING CORP.; Camera Model: E-500; Focal Length: 32.0mm; Aperture: f/9.0; Exposure Time: 0.0031 s (1/320); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure: Creative Program (based towards depth of field); White Balance: Auto; Light Source: Unknown; Flash Fired: No (Auto); Orientation: Normal; Color Space: sRGB.