Look for the lunar eclipse early Saturday

There will be a total lunar eclipse this Saturday morning.

There won’t be another such event until 2014. Unfortunately, this eclipse favors viewers living in Asia and the Pacific Rim; from Jamestown we’ll see the early stages of the eclipse, with totality occurring before moonset tomorrow.

The northeast corner of the moon will enter the penumbra (the Earth’s fainter outer shadow) at 5:30:53 a.m. tomorrow, but you probably won’t notice anything; at that time the moon will be 23.9 degrees over the southern horizon. By 6:05 a.m. the moon, which by then will be 18.3 degrees above the west-by-northwest horizon, will have penetrated far enough into the penumbra that you might notice that the upper left lunar limb looks wispy, almost as if faint clouds were scudding across its surface.

The same lunar rim will make contact with the umbra (the Earth’s darker inner shadow) at 6:44:21 a.m., when the moon will be 12.1 degrees above the west-by-northwest skyline. The umbra might appear to be blue or even turquoise at first contact because sunlight refracted through the Earth’s upper stratosphere passes through the ozone layer, which absorbs red light but passes on the blue.

As the moon goes deeper into the umbra, it will turn a bright orange to a deep red. There hasn’t been much volcanic activity this year, so dust in the Earth’s upper atmosphere will not absorb enough sunlight to prevent some of it from reaching the lunar surface. I saw a total lunar eclipse from Ohio on Dec. 30, 1963, before which a major volcanic eruption in Indonesia had dumped so much garbage into the atmosphere that the moon literally turned black and disappeared at mid-eclipse!

Totality begins with the moon fully within the Earth’s umbra at 8:04:28 a.m., but by that time the moon will be merely 0.6 degree above the west-by-northwest-by-northwest skyline. Because of the psychological and optical “moon illusion,” in which any moon near the horizon appears exceptionally large, the spectacle of a swollen and distorted orange or red moon setting might be awesome.

The moon will set while totality is in progress. It will be passing south of the center of the Earth’s umbra, so the magnitude of this eclipse is only 1.106, which means that this portion of our planet’s shadow covers just 1.106 times the moon’s diameter. Totality during this eclipse will last a scant 51 minutes. This is the second total lunar eclipse to take place this year; the first, which was not visible from the Americas, happened on June 15.

Full moon occurs Saturday at 8:36 a.m., when it is 180 degrees from the sun, and in this case, with the Earth between the two bodies. From the moon, you would see a total eclipse of the sun at this time!

The December full moon is called the “moon before yule” or the “long night moon” because evenings are longest around the winter solstice. Because the sun is lowest in the sky in December, and the full moon must be opposite the sun, it follows that the December full moon is the highest in the night sky.

(Bratton is a professor of history and political science at Jamestown College)

Tags: local news, news, eclipse