“The lunar halo display at right was taken from the roof of the Aurora Tower at Byrd Station.  This was a large box on legs about 30 feet above the snow surface where we made various measurements of the Aurora Australis.”

The halo cross is beloved of artists and illustrators but is in fact quite rare.   It was produced here by diamond dust plate crystals.   The horizontal band through the moon is a paraselenic circle, the lunar counterpart of the parhelic circle.    Moonlight reflected from near vertical plate/column crystal faces generated it.   The vertical halos are an upper and lower sun pillar produced from reflections off near horizontal plate crystal faces.

“The solar halo display at upper left was taken from the Byrd Auroral Substation about 40 miles from Byrd Station (the trail heading  to Byrd Station is visible in the photo).  The Substation was established to take simultaneous photos of auroral forms over a known baseline to determine their height.  The substation was closed just before the winter due to generator failure.  I spent the winter at Byrd Station.”

Ignore the inner ring - a lens artifact from the bright sun.     A faint and broad parhelic circle crosses the image and there is a faint 22 degree halo.  Two sundogs dominate the scene.    

Pillars descend downwards from the sundogs to the horizon.  The HaloSim ray tracing at right shows them linking the parhelia and below horizon subparhelia. They are mostly produced by rays entering a plate crystal side face, reflecting internally from the lower hexagonal face and then leaving through a side face inclined 60° to the first.