Circumhorizon Arc Over Sampacho, Argentina
November 30, 2016
The photos above shows a remarkable circumhorizon arc as observed over Sampacho, Argentina, just before noon on November 19, 2016. This particular arc is even more eye-catching because of the wavy sky. Circumhorizon arcs, perhaps the most colorful of all ice crystal-derived atmospheric phenomena, occur when sunlight is refracted through the pencil-shaped ice crystals found in cirrus clouds -- sunlight enters the vertical side face of a crystal and exits through a lower basal face. These arcs are parallel to the horizon, always on the same side of the sky as the Sun, but can only be viewed when the Sun is very high in the sky, around midday. Thus, at this time of year (November - February) they're best seen by residents in the Southern Hemisphere.
Photo Details: Top - Camera Model: Canon EOS REBEL T5i; Lens: 17-50mm; Focal Length: 17.0mm; Aperture: ƒ/8.0; Exposure Time: 0.0013 s (1/800); ISO equiv: 100; Software: Adobe Photoshop CC (Windows). Bottom - same except: Focal Length: 47.0mm; Exposure Time: 0.0006 s (1/1600).