Shadow of Acatenango and Anticrepuscular Ray

February 17, 2016


Photographer: Marvin Grijalva
Summary Authors: Marvin Grijalva; Jim Foster

Shown above is the shadow of the Acatenango volcano (13,044 ft or 3,976 m) in Guatemala as observed at sunset. From an elevated position, whenever the Sun is low in the sky it may be possible to see a mountain shadow projected on not only the distant landscape but the distant atmosphere as well. You'll have a better chance of noticing the shadow if the sky is laden with aerosols. In this case, the sky was dusty perhaps as a result of recent eruptions. Dust or ash particles outside of the shadow scatter sunlight, whereas scattered sunlight is absent on the inside of the shadow.

Of course, to the see the shadow you must be facing toward the antisolar point. On this late November afternoon, a conspicuous anticrepuscular ray, originating from a cloud in front of the Sun but on the opposite side of the sky, emerges from the antisolar point. Note that the Agua volcano can be seen at the far right. Photo taken on November 29, 2014.

Photo Details: Model: Canon EOS REBEL T3; Lens: EF-S18-55mm f/3.5-5.6 III; Exposure Time: 1/800; F Number: f/3.50; Exposure Program: Manual; ISO Speed Ratings: 100; Focal Length: 18mm.