Circular circumscribed halo
This high-sun picture by Dorothé Trompert was taken in Alice Springs, Australia, on 15 Nov 2005 13:17 LT. The solar height was 75°. Although the halo is almost circular, it is probably not the 22° halo itself. Instead, the strong peak in its intensity near the halo angle and its vivid colors indicates that it is a circumscribed halo. This observation supports my conjecture that in many of the historic reports of widely-noticed 22° halos the presence of a bright circumscribed halo contributed to its visibility. This happened, among other cases, with the so-called 'Chernobyl-halo' in 1986 and with Emperor Augustus's halo in 44BC.