Posts Tagged ‘lunar eclipse’

Watch the Dawn Eclipse of the Moon, Dec. 10, 2011

December 6, 2011 Leave a comment

Credit: Sky & Telescope photo by Richard Tresch Fienberg

Credit: Sky & Telescope photo by Richard Tresch Fienberg

If you’re anywhere in central or western North America, mark your calendar to get up before dawn this Saturday, December 10, 2011. That morning the full Moon goes through its last total eclipse until 2014.

The farther west you are in the U.S. or Canada, the better you’ll be set up for the show. If you’re in the Pacific time zone you can watch the Moon slip into Earth’s shadow completely, while the Moon is sinking low in the west-northwestern sky and dawn is brightening. In the Pacific Northwest and westernmost Canada, you can even see the Moon start to emerge from our planet’s shadow after the total eclipse is over — until moonset and sunrise end the show.

From roughly Arizona to the Dakotas, the Moon sets while it’s still totally eclipsed — though horizon obstructions and the brightening dawn may end your view somewhat before then.

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International Measure the Moon Night – Dec. 10, 2011

December 5, 2011 Leave a comment

This week’s total lunar eclipse will offer a rare opportunity for students, teachers, and the general public to measure the Moon’s distance and size duplicating the same techniques — with a Digital Age twist — used by Greek astronomers thousands of years ago.

On the night of December 10, The Classroom Astronomer (TCA) magazine will coordinate worldwide observations of the Moon’s position in the sky and its passage through the Earth’s shadow. (See Note 1 for regions of eclipse visibility.) These are key techniques — both now and in antiquity — for measuring the Moon’s diameter and distance from the Earth. The actual measuring methods are called the Shadow Method and the Lunar Parallax Method. TCA has created the website MeasureTheMoon.Org as a place for teachers — classroom and informal — students, and interested members of the general public to get information on how to measure the distance of the Moon (see Resources below).

The Shadow Method uses the transit of the Moon through Earth’s central shadow, the umbra. The angular size of the cross section made visible by the shadow on the Moon’s face is directly related to a unique distance. This was first accomplished by astronomers thousands of years ago, though they assumed a cylindrical shadow instead of the conical one we know it is today.

The Lunar Parallax Method uses a technique familiar to the ancient Greeks, triangulation, but which could not be done then because they could not communicate with observers far from Greece. Two observers today, thousands of miles apart, communicating via the Internet or telephone, can snap photos of the Moon at the same instant. They would see the Moon in front of different star fields, an angular shift directly related to the Moon’s distance and the distance between the observers.

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Moon’s Shadow, like a Ship, Creates Waves

October 2, 2011 Leave a comment

During a solar eclipse, the Moon’s passage overhead blocks out the majority of the Sun’s light and casts a wide swath of the Earth into darkness. The land under the Moon’s shadow receives less incoming energy than the surrounding regions, causing it to cool. In the early 1970s, researches proposed that this temperature difference could set off slow-moving waves in the upper atmosphere. They hypothesized that the waves, moving more slowly than the travelling temperature disparity from which they spawned, would pile up along the leading edge of the Moon’s path — like slow-moving waves breaking on a ship’s bow. The dynamic was shown theoretically and in early computer simulations, but it was not until a total solar eclipse on 22 July 2009 that researchers were able to observe the behavior.

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