Encore - Sun Pillar and Sundog

February 28, 2015

EPOD_EncoreSun Pillar and Sundog

Take a look back at some of the EPODs our viewers found particularly eye-catching. Today, and every Saturday, EPOD invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers’ Choice polls. Join us as we look back at these intriguing and captivating images.

Photographer: Aase Berg
Summary Author:
Ole Johan Løkberg; Aase Berg

The photo above shows both a sharp Sun pillar (left) and a striking sundog or mock Sun (right) as observed from Rugldalen, Norway. The bitter air on this winter's day was filled with hexagonal ice crystal plates that wobbled slightly around their horizontal position as they fell toward the surface. Sun pillars form when sunlight is reflected from the bottom or, occasionally, the top surface of aligned plate-shaped ice crystals. Sunlight that also passes through the side faces of these plates is refracted in such a way to form a sundog. However, in crystals where the side faces are not all normal to the direction of sunlight (not perfectly oriented), the refracted rays can be reflected from the crystal's top or bottom faces. These inside reflections in effect elongate the normal sundog "spot" into a shaft of light. This sundog's red-yellow color results from the color of the low Sun. Note that the sundog is approximately 22 degrees from the pillar and the unseen solar disk. Could sightings of such sundog pillars possibly be responsible for the "Pillars of Fire" appearing in many historical texts?