Tuesday, 7 February 2017
Another surface helic arc
This surface helic arc was seen on the last two days of January 2014 in Oulu. The photo below shows a "close-up" of the effect. One would think such a halo would be formed from simple external reflection, but that's not the case at least here. As exemplified by the one crystal that is in focus in the close-up photo below, the light went through the crystals. This was confirmed also visually. See more photos in first and second original posts in Taivaanvahti.
Jarmo Moilanen too observed this halo on the first day. In his observation the effect is distorted. That's probably because of a preferential orientational growth of the crystals on a windy sea shore.