Circumhorizon Arc Over Port of Tinos Island, Greece

June 07, 2019


Photographer: Stavros Hios
Summary Authors: Stavros Hios; Jim Foster

Of all the atmospheric optical phenomena, circumhorizon arcs are perhaps the most colorful. The one shown above was captured over Port of Tinos island, Greece on May 19, 2019. It caught my eye as an I was sipping a cup of coffee while looking out over the Aegean Sea. Sometimes called fire rainbows, they’re seen below the Sun and can only be viewed, in the mid-latitudes, from mid-spring to late summer. In addition, they can only be observed at midday. They form when hexagonal ice crystals in cirrus clouds are oriented in such a way that that sunlight enters the side face of these plate-shaped crystals and then exits through the lower basal face.

Photo Details: Camera: NIKON D750; Software: Adobe Photoshop CS5 Windows; Exposure Time: 0.0008s (1/1250); Aperture: ƒ/16.0; ISO equivalent: 640; Focal Length (35mm): 24