column crystals) or a 46° circular halo. The Birmingham all-sky image is here overlaid with dots
from a simulation for the sun's altitude in Birmingham at 12.35 UTC (23°).
The red dots are the supralateral arc and upper tangent arc. Blue dots 46° halo. Green dots parhelic
circle.
The overlay was fitted to the positions of the upper tangent arc and parhelic circle. It makes assumptions
about the orientation of the camera and the correspondence of the lens and simulation projections.
The arc in the photograph curving downwards to the campus clock tower best fits the supralateral
arc.
A supralateral arc is also consistent with the comparatively weak 22° halo and very strong upper
tangent arc.
