Halo Over Murrieta, California
March 20, 2017
Photographer: Mark Ritter
Summary Authors: Mark Ritter; Jim Foster
Featured above is an attention-getting 22 degree solar halo, an upper tangent arc (tangent to the top of the halo) and sundogs (on the sides of the halo and at the same elevation as the Sun). It was observed over Murrieta, California, on February 2, 2017. Sunlight passing through hexagonal plate ice crystals in cirrus clouds form the 22 degree halo and the arcs seen here. Because the crystals are oriented horizontally (think of a leaf as it falls to the ground) when they're positioned at the same elevation as the Sun and approximately 22 degrees from the solar disk their particular alignment allows this segment of the halo to be considerably brighter than the remainder of the halo. In addition, since the oriented crystals that form the sundog tend to be larger than the randomly oriented crystals that generate the 22 degree halo, they're generally much more colorful. Sundogs can be seen best when the Sun is low in the sky -- they cannot be viewed when the Sun attains an elevation of 61 degrees. Note also the contrail and its distinct shadow.
Photo Details: Camera Model: Canon EOS 5D Mark III; Lens: EF24-105mm f/4L IS USM; Focal Length: 24mm; Aperture: ƒ/16.0; Exposure Time: 0.0020 s (1/500); ISO equiv: 100; Software: Adobe Photoshop Lightroom 6.8 (Macintosh).