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Posted by jcconwell in Astronomy, moon.
Tags: , ,

On Dec. 21st, the first day of northern winter,  the full Moon passes almost dead-center through Earth’s shadow. For 72 minutes of eerie totality, an amber light will play across the snows of North America, throwing landscapes into an unusual state of ruddy shadow.

The eclipse begins on Tuesday morning, Dec. 21st, at 12:33 am CST (Monday, Dec. 20th, at 10:33 pm PST). At that time, the moon passes through the Earth’s shadow, will appear as a  bite at the edge of the lunar disk. It takes about an hour for the shadow  to expand and encompass the entire Moon. Totality commences at 01:41 am CST (11:41 pm PST) and lasts for 72 minutes.

For the best time for a quick look on a cold night –  it is December, after all –  choose this moment: 01:17 am CST (17 minutes past midnight PST). That’s when the Moon will be in deepest shadow, with a deep red color.

Why the deep red color? If you were on the moon you’d see the Earth cover the Sun, but instead of seeing black, you’d see the remaining sunlight pass through the Earth’s atmosphere around the Earth’s rim. A world wide sunrise or sunset. The light passing through so much atmosphere causes Raleigh scattering. The blue light is scattered out, causing the blue skies we see on Earth. What is left over is the red. Red sunsets, and red light hitting the moon, causing it’s deep scarlet glow.



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