Iridescent Clouds Over Elikonas Mountain, Greece

April 05, 2018

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Photographer: Tsouras Panagiotis 
Summary Authors: Tsouras Panagiotis; Jim Foster

These stunning iridescent clouds were captured near Livadeia, Greece, late in the day (05:35) on February 14, 2018. The silhouetted mountain in the foreground is part of Elikonas mountain of south-central Greece. An iridescent cloud can be thought of as a separated portion of a solar corona. Like the corona, the process responsible for the metallic hues is diffraction (cloud droplets) and not refraction (raindrops and ice crystals). Sunlight is diffracted around the outer edges of the droplets that compose mid-level clouds. It's the interference by the minute droplets that result in the overlapping of color orders that give the pastel purples, pinks and greens. Note that only the outer fringes of the clouds shown above exhibit color, which is either an indication of the very uniform droplet sizes here or perhaps well-defined graduation in the sizes of the droplets with depth into the center of the cloud. Since iridescent clouds are found in the vicinity of the Sun, make sure to protect your eyes when looking at them.

Photo Details: Camera: NIKON D750; Software: Adobe Photoshop CC (Windows); Exposure Time: 0.0004s (1/2500); Aperture: ƒ/9.0; ISO equivalent: 100; Focal Length (35mm): 300; Lens: 28.0-300.0 mm f/3.5-5.6.