Monday night December 20th, we get to witness a very exciting astronomical spectacle, a Total Lunar Eclipse. This one promises to be a special one, capping the longest night of the year with the strange and beautiful view of the full Moon being blotted out by the shadow of the Earth. The geometry of an eclipse is fairly textbook, but the experience is quite dramatic. This eclipse will be visible from the western hemisphere, meaning that anyone on the entire night side of Earth will have a view of the full Moon and will see the phases of the eclipse. In this particular eclipse, the Moon passes through the darkest part of the Earth's shadow (umbra) meaning that the entire surface of the Moon will no longer have direct sunlight shining on it, but because of the atmosphere of the Earth, refracted rays of sunlight will in fact bend around the Earth and illuminate the Moon, creating a trademark orange or reddish color on the Moon, an eerie effect indeed. The excellent NASA Eclipse Website has much more detailed information on the eclipse.
The event starts at 10:33 pm in San Francisco, as the partial phases of the eclipse take about an hour. The period of "totality" when the entire surface of the Moon is dark, lasts about an hour from 11:41 pm until 12:53 am, and then the Moon is slowly revealed again for another hour. Cross your fingers for good weather, dress warmly, and enjoy this fascinating spectacle of nature. And if you have binoculars or a telescope, use them - this is exactly the time to get a close-up look at one of the wonders of the sky.
Image courtesy of the Universe Today.
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