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Thursday, December 16, 2010

Our Winter Clouds

Fair weather winter clouds in the Negev are almost always thin cirrus. These thin clouds are white to light grey ice crystal clouds that cross but do not cover the sky. These clouds form when there is moisture at high levels and the temperature there is colder than freezing.

Thin cirrus over Mitzpe Ramon

In the evening these clouds, however thin, can always be noted by the circular rainbow they create around the moon, the result of the ice crystals refracting the moon's light. These clouds can also be quite deceptive, since they leave large portions of the sky uncovered and when very thin are invisible at night except for the dimming of the stars they cause. But once you get into a dark zone, you can immediately see they are trouble. A number of times I have gone out to my dark sky location, only to notice high, thin cirrus after arriving. But it's a small price to pay for the mostly clear, clean skies we have here in general.

Thin cirrus over the Club Ramon Hotel

Wishing you clear skies and fair viewing.

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