On January 25, 2017 I observed a reflection subsun in Auburn, California. This was my second observation of this phenomenon, the first of which was on February 1, 2008 and is already documented here.
Author: Steve Sumner
In the previous post of this display I discussed two photos taken towards the end of the hunt, just before twilight. Now it is time to look at the photos taken earlier, from midnight onwards at another location. Please mouse over or click the photos to remove the milky veil that the systems adds as default to them.
Of the several stacks that were photographed, I made simulations of two that are shown below. Unlike the morning photos, now only one stricly oriented Parry population was needed to the explain the display’s halos from c-axis horizontally oriented crystals. So here we have a pure case of uppervex Hastings and nothing reminescent of Wegener.
The mystery deepens. In two previous posts we wondered why some displays are great in their column orientation halos even though the crystals have well caved ends. Here we show a case that appeared on November 22, 2015 in Rovaniemi, where crystals seem not much different, yet rare halos requiring basal faces are completely absent. Even the 46° supralateral arc gives just a whiff. Poor crystal orientations can’t explain the absence of rare halos as the tanget arc is quite sharp. Had we known only about this display, we would be quite happy to explain with cavities, but knowing about the other displays, it is quite puzzling.
Marko Mikkilä, Jarmo Moilanen, Marko Riikonen
The diamond dust season is soon to arrive in Finland and it is time to wipe the dust off the equipment. In a meanwhile, here is the last winter’s starter for Rovaniemi, on October 30. The temperature during the display was -5° C, a quaranteed number for great stuff.