Orion Grabs the Ring

December 14, 2016

LunarHalo (3)

Photographer: Alan Beeler
Summary Authors: Alan Beeler; Jim Foster
For years my family has enjoyed an annual winter sojourn from cool, wet Willamette Valley in Oregon to the dark sky community of Borrego Springs, California, near Anza-Borrego Desert State Park. One evening, while heading out for an after-dinner walk we noticed the best ring around the Moon we had ever seen. I dashed back into our rental unit, rousted others from their after-dinner snooze and grabbed a camera. This broad ring is known as a 22 degree lunar halo. It forms when moonlight interacts with the hexagonal ice crystals that compose thin cirrus clouds. Note that for the complete halo to be viewed these crystals have to be somewhat randomly oriented and must fill the sky across the region where the Moon (or Sun) is positioned.

Orion can be seen on the edge of the ring at right center (Betelgeuse is just inside the ring), and the brightest star in the sky, Sirius, is just to the right of the right-most palm. Photo taken on February 18, 2016, at 7:43.

Photo Details: Camera Maker: OLYMPUS IMAGING CORP; Camera Model: E-M1; Lens: OLYMPUS M.7-14mm F2.8; Focal Length: 9mm (35mm equivalent: 18mm); Aperture: ƒ/2.8; Exposure Time: 10.000 s; ISO equiv: 200; Software: Adobe Photoshop Lightroom 6.7 (Windows).