Astronomy Picture of the Day

Explanation: The total phase of the June 15 lunar eclipse lasted an impressive 100 minutes. Its entire duration is covered in this composite of a regular sequence of digital camera exposures, tracking the dark lunar disk as it arced above the Acropolis in Athens, Greece. In fact, around 270 BCE Greek astronomer Aristarchus also tracked the duration of lunar eclipses, though 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. A more modern Greek astronomer, Elias Politis titled this eclipse duration study and the accompanying youtube timelapse video "Acropoclipse".