What's New 
  Rays & Shadows
  Water Droplets
  Ice Halos
    Frequent Halos
    Infrequent Halos
      Why infrequent?
      46° Halo 
      Parry Arcs
      Lowitz Arcs
      Moilanen Arc
      Kern Arc
      120° Parhelia
      44° Parhelia
      Subhorizon Arcs
        Circular Halos
          23° Upper Arc
    Multiple Displays
    Other Worlds
    Observing Halos
  High Atmosphere
  Links & Resources
  Search - Index


   Pyramidal Crystal Parhelia 


Parhelia of oriented pyramidal crystals.

When ice crystals take shapes similar to that shown they can be oriented and then produce exotic 'parhelia' very unlike the familiar sundogs of ordinary plate crystals.

The display at left has crystal tilts of 1� (std deviation) and they create many odd parhelia.

Rather poor crystal orientations can still produce parhelia arcs. The crystals in the display at right had their tilts increased to 15� at right yet some parhelion arcs survive, particularly the extremely bright and colourful 23° 'upper parhelion' above the sun.

The pyramidal parhelia are named after the equivalent circular halo ray path but, like ordinary sundogs, they are not necessarily at that distance from the sun. Thus, the uppermost arc is a 23� parhelion but it lies above the 23� circular halo and its distance depends on the solar elevation.

Simulation: sun centered fisheye with the sun 30� high.  50% of crystals were randomly oriented in order to produce the 9,18 and 23� circular halos.