Brocken Spectre on Mount Etna

December 19, 2018

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Photographer: Cesare Scalia 
Summary Authors: Cesare Scalia; Jim Foster

Shown above is a classic Brocken spectre observed on Mount Etna, Italy, on September 24, 2017. The colorful rings are the glory and the extended shadow, which happens to be mine, is the Brocken spectre. Look for this phenomenon whenever you're in the mountains (or on the deck of a tall building) and enshrouded by a layer of fog. Diffraction of sunlight by the tiny fog droplets is responsible for both the spectre and the glory. To observe them, though, the Sun must be at your back and shining down upon the fog layer. My shadow is projected through the mist, and like all shadows converges toward the antisolar point. Perspective makes the shadow appear triangular.