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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

See Explanation. Clicking on the picture will download the highest resolution version available.

Kalamalka Lake Eclipse

Explanation: Recorded on August 28th , this serene total lunar eclipse sequence looks southwest down Kalamalka Lake toward the lights of Coldstream , British Columbia. An exposure every 4 minutes captured the Moon's position and eclipse phase, until the Moon set behind the town lights and a hill on the horizon. In fact, the sequence effectively measures the duration of the total phase of the eclipse . Around 270 BC, the Greek astronomer Aristarchus also measured the duration of lunar eclipses - though probably without the benefit of digital clocks and cameras. Still, using geometry, he devised a simple and impressively accurate way to calculate the Moon's distance, in terms of the radius of planet Earth, from the eclipse duration.

Date September 1, 2007
Credit Credit & Copyright: Yuichi Takasaka
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.