A 24°-halo is a white ring of light with a radius of 24° around the sun. It often appears together with other halos caused by pyramid-shaped ice crystals. As it lies very near to the 22°-halo it can often be recognized only by the unusual width of the 22°-halo and/or by the double sequence of the spectral colours or at least of its red part.
Simulation of pyramidal halos.
Grafik: W. Tape; Atmospheric Halos; S. 89; Am. Geophysical Union; 1994
A 24°-halo is caused by randomly orientated pyramid-shaped ice crystals. The path of light can be seen in the diagram above.