Anti-crepuscular Rays

By: Juan Carlos Casado


Region: Europe

Site: Tenerife - Spain

Date: December 2008

The panoramic view shows the twilight sky from Altavista's refuge (3270 m altitude) located on the way to the top of Teide volcano, Canary Islands. On the profile of the mountain in the center the domes of Teide Observatory are visible as brighter points, and to the right one can see the Grand Canary island. Anticrepuscular rays are similar to crepuscular rays, but seen opposite the sun in the sky. Sunlight travels in straight lines, but the projections of these lines on Earth's spherical atmosphere are great circles. Hence, straight-line crepuscular rays from a setting (or rising) sun can appear to re-converge at the antisolar point. Anticrepuscular rays are most frequently visible near sunrise or sunset. Crepuscular rays are usually much brighter than anticrepuscular rays. This is because for crepuscular rays, seen on the same side of the sky as the sun, the atmospheric light scattering and making them visible is taking place at small angles. Juan Carlos Casado,

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