Descending Sundogs

The appearance of a sundog changes slightly with altitude. Higher in the sky it is splayed outwards from the sun but nearer the horizon the appearance is more vertical.

These images taken over 70 minutes show a sundog at solar altitudes of 21, 16 and 11 degrees.

As the solar altitude increases the light has to travel a slightly different path through the crystals to get to your eye. The distance of the sundog from the sun increases more quickly with altitude so that the top of the sundog is skewed outwards.

Solar altitude 21 degrees.

The top part of the sundog is missing because of a hole in the cloud, even so the colour band is clearly not quite vertical.

Solar altitude 16 degrees.

The colour band is almost vertical now, with hints of 22 degree halo above and below.

Solar altitude 11 degrees.

Canon EOS 20D   24th July 2007
Wiltshire, England

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