The halo’s angle from the sun

The full halo with circles added showing the angular separation from the sun.

The height of this image is 2160 px. The photograph was taken on a Canon EOS 7D with the EF-S 15-85 mm lens set to 15 mm focal length. That gives a vertical field-of-view of 52.5°. From that information, we find the angular separation of the halo from the sun to be around 21.6°.