Tangent Arcs and Weak Circumhorizon Arc

These upper and lower tangent arcs were quite strong. Although the sun was high enough for them to link up as the circumscribed halo this wasn't clear, and there was only a trace of the full circular 22 degree halo.

An even more subtle feature was a hint of circumhorizon arc, about a quarter of the way up the images below. It was hard to be sure it wasn't just reddening by haze but the increased contrast in the right image confirms its identity. Conditions were hardly ideal with this milky cirrus and at 60 degrees altitude the sun was barely high enough.

Canon EOS 20D 29th May 2008
Wiltshire, England