eclipse

Total Lunar Eclipse – December 21, 2010

Article Updated: 24 Dec , 2015

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Both lunar and solar eclipses can only occur when the Earth, Sun and Moon are directly aligned… and that alignment is about to happen just four days before Christmas! While the winter treat of totality will lend itself to North America, many other parts of the world will be able to enjoy a partial eclipse as well. Just remember your time zones and I’ll post specific times and locations just a little closer to the date. Right now, let’s learn more!

What is a partial eclipse or totality? When the Earth’s shadow engulfs the Moon, it is a lunar eclipse which occurs in two phases. The outer shadow cone is called the penumbra and the dark, inner shadow is called the umbra. A round body, such as a planet, casts a shadow “cone” through space. When it’s at Earth, the cone is widest at 13,000 kilometers in diameter, yet by the time it reaches the Moon it has narrowed to only 9,200 kilometers. Considering the distance to the Moon is 384,401 kilometers, that’s hitting a very narrow corridor in astronomical terms!

As a rule of thumb, remember that the Moon moves about its own diameter each hour, so the very beginning of a penumbral eclipse will be difficult to notice. Slowly and steadily, the coloration will begin to change and even inexperienced eclipse watchers will notice that something is different. The Moon will never completely disappear as it passes through the Earth’s umbral shadow cone, either. Thanks to our atmosphere bending the sunlight around us, it scatters the light and refracts the signature red and copper coloration we associate with lunar eclipse. Why? Just the small particles in our air – dust and clouds – the shorter wavelengths of light from the Sun are more likely to be scattered (in this case, red) and that’s what we see. Exactly the same reason sunset and sunrise appears to be red! If you’d like to dedicate a portion of your mind to science, then try judging the eclipse coloration on the Danjon scale. It was was devised by Andre Danjon for rating the overall darkness of lunar eclipses:

L=0: Very dark eclipse. Moon almost invisible, especially at mid-totality.
L=1: Dark Eclipse, gray or brownish in coloration. Details distinguishable only with difficulty.
L=2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright
L=3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L=4: Very bright copper-red or orange eclipse. Umbral shadow is bluish and has a very bright rim.

Now we know what to plan for! Time to get your winter gear ready. Photographing or video taping an eclipse is easy – but remember if you live where it is very cold that your batteries will expire fast – so keep an extra set in a warm place next to your body.

Be sure to check back for specific times and locations here at UT on December 20th… and tell your family and friends about the very special Christmas present that’s coming your way!

Eclipse Images Courtesy of Doug Murray (top), Tom Ruen (bottom) and NASA (center illustration). We thank you!


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Jon Hanford
Member
Jon Hanford
December 14, 2010 5:06 PM
Tammy, thanks for getting the word out for the upcoming lunar eclipse. The last total lunar eclipse for the continental US was back in February of 2008 & the next won’t occur till April 2014. As usual, Fred “Mr. Eclipse” Espenak has an excellent overview of the upcoming event: http://www.mreclipse.com/LEdata/TLE2010Dec21/TLE2010Dec21.html Included are lunar eclipse diagrams with the times of various stages of the eclipse, more info on making brightness estimates (using the aforementioned Danjon brightness scale), info on crater timings and how to measure them, and tips on how to photograph the event. All that’s needed now is some cooperation in the weather department. Note: This total eclipse happens to occur (coincidentally) at nearly the same time as… Read more »
gopher65
Member
gopher65
December 14, 2010 6:40 PM

Thanks for the article.

Bah, I wish that this was happening at a more convenient time (for mewink). I might get up to snap a few pictures if it isn’t -40 outside that day. Maybe I’ll just go to work 4 hours early.

Tim McDaniel
Member
Tim McDaniel
December 14, 2010 10:41 PM

No, a eclipse of the Moon is when the Sun passes between the Earth and the Moon.

That’s according to _Science Made Stupid_, an _Airplane!_-quality parody of every bad science popularization article and book you’ve ever seen. It also says that an eclipse of the Sun is when the shadow of the Earth passes over the Sun, and an eclipse of the Earth is when you put your hands over your eyes.

Run
Member
Run
December 15, 2010 1:55 AM

What is the reason for the variation in coloration of the moon during a lunar eclipse? Is it to do with how close to the core of the umbra the moon comes, or is it to do with the amount of light getting through the atmosphere (due to cloud cover etc)?

ricktheruler
Member
ricktheruler
December 15, 2010 9:34 AM
My Birthday’s December 19, so I’am leaving my reasearch observation Richardo Brown: Signature installed and instrimented on the Lunar Reconnanse Orbiter C.D. Rom Observation: Craters dot the moon’s surface. Materials thrown from impacts that made them centers radial patterns of bright ejecta with scars left over by objects that smashed the earth in our early solar system of the star: Sun. The largest are the impact basins, enormous craters raning up to around (1,553mi) across. Lava flooded the basin floor sometime after titanic collisions formed them, creating the smooth, dark surfaces that the eye grography maps as Marias or Seas. Blocks of rock hurled formed with impacts gathering nd becoming larger made what is called the satelite of… Read more »
Jon Hanford
Member
Jon Hanford
December 15, 2010 1:56 PM

ricktheruler,

You forgot Apollos 14, 15 & 17, twice! Add to that Apollos 8, 10 & 13, that flew in close proximity to the moon.

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