Halo Display

After months without so much as a good sundog we had this nice halo display. It might not compare with a diamond dust display but when you consider that tens of kilometres of sky need to be filled with the right kind of ice crystals it is remarkable that we see large haloes at all.

From top to bottom; circumzenithal arc, supralateral arc, upper tangent arc, 22 degree halo, sundogs.

Circumzenithal and supralateral arcs at top with upper tangent arc below.

The upper tangent arc showed the distinctive gull wing shape because the sun was 18 degrees above the horizon at the time.

A little later and the circumzenthal arc strengthened, along with the top of the supralateral arc. The upper tangent was barely visible, but for a short while there was a strong sundog.

Circumzenithal and supralateral arcs

Sundog in a wisp of cirrus

A weak supralateral arc curves from the circumzenithal arc, at upper right, downward across the middle of the image.

Stretching down from the sundog is a section of halo which doesn't seem to have the right curvature to be part of the 22 degree halo.

Canon EOS 20D   1st March 2009
Wiltshire, England

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