Midnight Sun at Deadhorse, Alaska

November 07, 2007

Midsun

Provided and copyright by: James Kaler, Astronomy Department, University of Illinois
Summary authors & editors: James Kaler

The midnight Sun shines over Lake Colleen at Deadhorse, Alaska, just south of Prudhoe Bay on the Arctic Ocean. This photo was taken on July 7, 2007. In early July, the Sun is still so far north (22.6 degrees north of the celestial equator) that it stays up 24 hours a day. A circumpolar Sun is possible only above the Arctic Circle (66.6 degrees north) or below the Antarctic Circle (66.6 degrees south) because of the 23.4 degree tilt of the Earth's axis relative to the orbital perpendicular. The Sun sets near the end of July here as it appears to move south along the tilted ecliptic. A latitude of 70.2 degrees north gives an actual solar (center) elevation of 2.8 degrees -- this is raised to 2.9 degrees by atmospheric refraction which lofts all celestial objects upward from their true positions. Note the glitter patch on the lake surface.

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