Thursday, 1 April 2010
Halo display from Ghana
For a change a display from Africa. This was see in Accra, Ghana, on 10 March this year. The photo was taken by Kwaku Chintoh.
Sun is at 75.5 degrees elevation. The two sun concentric halos are rather 9° column arc and circumscribed halo than 9° and 22° halos. That is because of their sharpness - circular halos from randomly or very poorly oriented crystals are expected to be more diffuse. There is also parhelic circle.
In the simulation column oriented prismatic and pyramidal crystals were used. Pyramid crystal tilts are 7 degrees. Simulation was made with HaloPoint2.0 -software. Parameter-file is available ( 1 )