If you live in North America or western South America, you have a treat in store for you tonight or early tomorrow morning: a total lunar eclipse!

 Total lunar eclipse, photographed at the Public Observatory at the National Air and Space Museum on December 21, 2010.   

If you live elsewhere in the world, or if it’s cloudy in your location – as it probably will be tonight at our location in Washington, DC – you can still see the eclipse online.  Several websites will host live streams.  Some of their locations will be clouded out, so we recommend that you search for “lunar eclipse live stream” and browse the results.  You can also participate in a live web chat during the eclipse with NASA astronomers.

Tonight’s eclipse begins at 12:53 am EDT, very early in the morning of April 15 for the East Coast.  That’s when the Moon enters the partial shadow of the Earth, called the penumbra.  During this part of the eclipse, the Moon will still look like an ordinary full Moon, because only a slight and subtle shadow is cast on the Moon.

The dramatic part starts at 1:58 am EDT (or 10:58 pm PDT on April 14 for the Pacific Coast). As the Moon starts to enter the full shadow of the Earth, called the umbra, skywatchers will see a bite taken out of the Moon.  As the hour goes on, the bite gets bigger and bigger.  Earth’s shadow on the Moon has a fuzzy edge (as seen in the image above) because of Earth’s atmosphere.

This shows the geometry of a lunar eclipse. When the Sun, Earth, and Moon, are precisely aligned, a lunar eclipse will occur. During an eclipse the Earth blocks sunlight from reaching the Moon. Earth creates two shadows: the outer, pale shadow called the penumbra, and the dark, inner shadow called the umbra.  The eclipse is noticeable once the Moon enters the umbra. 

At 3:06 am EDT (12:06 am PDT), the Moon will pass completely into Earth’s shadow.  But it won’t vanish!  The light of all the sunrises and all the sunsets around the world will be filtered through Earth’s atmosphere and fall onto the Moon, giving the full Moon an eerie, blood-red tint.  The color depends on what’s happening in the Earth’s atmosphere. Volcanic activity, for example, can lend the Moon an especially vivid hue.

At 4:24 am EDT (1:24 am PDT), a bright sliver will appear again as the Moon starts to leave the Earth’s umbra.  That part of the eclipse will last until 5:33 am EDT (2:33 am PDT), when the Moon will look fully illuminated again, though it will still be in the Earth’s fuzzy, subtle penumbra until 6:37 am EDT (3:37 am PDT).

You can watch the eclipse with a telescope or binoculars, or just with your eyes!  Unlike for a solar eclipse, no safety equipment is needed. You’ll see even more with your eyes than shown in the image sequence above. The human eye is better at seeing a range of bright and dark areas than a camera, so while sunlight is illuminating part of the Moon, you will still be able to see the darkened part. Also, if you miss tonight’s eclipse, just mark your calendars!  Tonight is the first in a sequence of four consecutive total lunar eclipses (called a tetrad) which will each be visible from all or part of the United States.  The next three total lunar eclipses will occur on October 8, 2014, April 4, 2015, and September 28, 2015. We hope you’ll share your photos of tonight’s eclipse with us!

Related Topics Astronomy Moon (Earth)
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