These events, which I describe in more detail in my book Marking Time (Wiley, October 1999), seem to have been set in train by a combined Sun pillar and parhelic circle seen by Constantine and his men almost 1,700 years ago.
Your item in the May issue on computing Sun pillars (bright columns of light in the sky produced by reflections from atmospheric ice crystals) gave an interesting account of the modern understanding of their origin.
Close to sunset or sunrise, when the Sun angle is best for forming a Sun pillar, the sunlight will have an orangish tint.
These angles provide the top and bottom edges of the Sun pillar for a given solar angle and crystal orientation; the angles are relative to the horizon.
Some, namely sundogs and Sun pillars
, are more often spotted, especially when they appear low in the sky during morning or evening commutes from school and work.
Other eerie and lovely halo effects - such as streetlight pillars resembling auroral rays and sunstreaks like downward sun pillars
in front of the landscape - can occur in falling showers of small, simple snow crystals that sometimes sparkle like diamond dust.
Sky & Telescope readers respond to our requests with stunning photographic studies of halos, Sun pillars, and other atmospheric sky phenomena.
Werner Hasubick sent photographs of Sun pillars taken from his home at Buchloe in southern Bavaria.
Sun pillars are caused by reflection, not refraction, so they themselves are colorless -- but they take on, often beautifully, the gold, orange, or red of the low Sun producing them.
Most Sun pillars are caused by reflections off the faces of flat, hexagonal, plate-shaped crystals floating horizontally.
My best-ever Sun pillar extended 5[degrees] below the Sun and a mighty 22[degrees] above it, where it was crowned by an intense, multicolored "upper tangential arc.
Sun pillars are caused by sunlight reflecting off the faces of flat, hexagonal ice crystals floating nearly horizontally.