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






 
123456789012345678


   Pyramidal upper parhelion 


Lone Arc. This bright and colourful arc was the only halo apparent in the sky ~ Norfolk, England 5th July 2000, 16.55 - 17.35 UT sun 28-22 high. The image, however, also shows a faint circular halo beneath the arc. Image 2000 Les Cowley.

Pyramidal 23 upper parhelion or Parry arc? The HaloSim simulation includes pyramidal crystals and Parry oriented columns. Both arcs are similar but the 23 parhelion best matches the photographs and visual appearance. The very faint circular arc could be a 23 or 22 halo. Thanks to Walter Tape and Jarmo Moilanen for help with the identification.
  Ray path for 23 upper parhelion. The crystal is oriented with its large pyramidal end pointing downwards. Rays enter the near horizontal top face and leave through one of the lower pyramidal faces. The path is very 'efficient' and generates a bright arc which survives quite large crystal tilts from vertical.