Sundog in Thin Cirrus

Where sundogs form in small patches of cirrus their shape can change dramatically over a few minutes. This sequence is at roughly three minute intervals.

The very fine structure in this patch is quite striking.

More of the sundog becomes visible as the cloud moves to the right.

The faint section above it is more likely to be an extension of the sundog than a portion of 22 degree halo. At 16 degrees altitude the halo would still be slightly left of the sundog.

The core of the sundog is now less distinct and the vertical brightness is more even. Whether this is due to greater tilts of the crystals or just the spread of cirrus is hard to tell.

Canon EOS 400D   18th July 2007
Wiltshire, England

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