NOCTILUCENT CLOUDS (NLC's)
Known as noctilucent (meaning "night shining"), these clouds occur at extreme
altitudes (around 85km above the Earth's surface) and are often visible from the far
northern latitudes between May and August during the persistent twilight of the night.
They are visible because they remain in sunlight (at their high altitude) although
the sun is below the horizon for the observer on the ground.
Here are a few examples. Note- the lights visible in the clouds are not UFO's, but internal reflections of the bright terrestrial lights in the lens!
See the outstanding displays of July 2003, June 25-26th and July 6-7th 2004.
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A nice example of noctilucent clouds taken over Falkirk in August 1998; 2 sec exposure through a 50mm lens at f/1.4. |
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A conspicuously bright display imaged just before midnight on the 13th July 2002. It had been a poor season from my location, but this was a nice event; 3 sec exposure through a 180mm lens at f/2.5. |
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The display above imaged from another location about half an hour later. Note changes in structure and brightness; 3 sec exposure through a 135mm lens at f/2.8. |