Home   OPOD   What's New    Rays & Shadows   Water Droplets   Rainbows   Ice Halos     Contents     Crystals     Frequent Halos       22° circular       Sundogs       Tangent Arcs       Circumscribed         Solar altitude         Images       Pillars       Circumzenithal       Circumhorizon       Parhelic Circle     Infrequent Halos     Multiple Displays     Other Worlds     Observing Halos     HaloSim   High Atmosphere   Links & Resources   Search - Index   123456789012345678		Circumscribed Halo - solar altitude
		Upper and lower tangent arcs and a faint 22º halo. HaloSim3 simulation. The region below the horizon is dark blue.   Changing shape of the circumscribed halo with solar altitude. Mouse slowly over the slider to see the changes. The halo "starts" at a sun elevation of 29º as the joined form of the upper and lower tangent arcs. It has a pronounced drooping distorted oval shape until the sun reaches ~50º high. Often only the brighter upper and lower sections are visible. When the sun is higher, the halo approaches the 22º halo more and more closely and it becomes exactly circular when the sun is overhead. At high sun it is not easy to tell the circumscribed and the 22º halos apart. The circumscribed halo has somewhat brighter and purer colours because rays through the singly oriented columns producing it give less colour overlap than those through the much less oriented crystals making the 22º halo..