Copper Moon before Dawn

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Copper Moon before Dawn

By: Dave Laney

Before sunrise on Feb 21st, the moon will pass into the Earth's shadow resulting in a full lunar eclipse. Total eclipse will be visible in the predawn sky from anywhere in South Africa, although in the eastern coastal regions the moon will set a bit before totality is over. Total eclipse will last from 05:00 to 05:50.

Ring of Fire, Copper Moon

The full moon of February 21st will be 'eclipsed' as it passes through the Earth's shadow, but it won't be completely dark. A totally eclipsed moon usually appears copper-orange to red, for the same reason that the western sky looks orange-to-red after sunset. The Earth's atmosphere bends the sun's light so that some light always reaches the surface of the moon. What gets through is mostly red light. An observer on the moon would see the Earth as a dim moonlit disk passing in front of the sun, surrounded during total eclipse by a glowing red-orange ring.

Last chance until 2015

Total lunar eclipses occur on average about twice every three years, but there can be 0 to 3 in a given year. There will be none next year, and the next total eclipse visible from South Africa isn't until 2015. Don't miss it!

Eclipse times and the shadowy background

The Earth's shadow has two parts. In the `penumbra', direct sunlight is only partially blocked. When the moon enters the penumbra at 02:35, it will begin getting dimmer, but the effect will be impossible to see by eye. At 03:43 the moon will begin to enter the `umbra', the much darker part of the shadow where direct sunlight is completely blocked and only the red glow of the Earth's atmosphere lights the moon. The upper right side of the moon will begin to darken, and it will look as though some of the moon is missing. By the time all of the moon is inside the umbra, at 05:00, it will have changed colour, looking dim and amber to copper. The lower left edge of the moon will be the brightest part at this moment, since it is only just inside the umbra.

This `total' phase of the eclipse lasts only until 05:50, when the upper left edge of the moon starts to leave the umbra. For all but the east coast of South Africa, this is still a bit before moonset and sunrise. The moon leaves the umbral part of the Earth's shadow at 07:09, and the eclipse ends when the moon leaves the penumbra and returns into full sunlight at 08:17, but by the time these events occur, the moon will have set even in the westernmost parts of southern Africa.

More information:

For further details contact Dave Laney at:
Tel: 021 447 0025
Fax: 021 4473639
E-mail: cdl@saao.ac.za