Monday, December 20, 2010

Events, Earth Northern Hemisphere | Total Lunar Eclipse, December 21

Today and tomorrow (winter solstice) are very busy days for sky observers.

Stargazers from the Northern Hemisphere tonight will be entertained by a total lunar eclipse, happening right at winter solstice ---a sky event which was not happening since 1638!

Below is more information, courtesy of NASA, for those of us who will venture in the frigid northeast night to document it or just enjoy this very special moment in the universe:

"The Moon's orbital trajectory takes it through the northern half of Earth's umbral shadow. Although the eclipse is not central, the total phase still lasts 72 minutes. The Moon's path through Earth's shadows as well as a map illustrating worldwide visibility of the event are shown in Figure 4. The timings of the major eclipse phases are listed below.

Penumbral Eclipse Begins: 05:29:17 UT
Partial Eclipse Begins: 06:32:37 UT
Total Eclipse Begins: 07:40:47 UT
Greatest Eclipse: 08:16:57 UT
Total Eclipse Ends: 08:53:08 UT
Partial Eclipse Ends: 10:01:20 UT
Penumbral Eclipse Ends: 11:04:31 UT

At the instant of greatest eclipse (08:17 UT) the Moon lies near the zenith for observers in southern California and Baja Mexico. At this time, the umbral magnitude peaks at 1.2561 as the Moon's southern limb passes 2.8 arc-minutes north of the shadow's central axis. In contrast, the Moon's northern limb lies 8.1 arc-minutes from the northern edge of the umbra and 34.6 arc-minutes from the shadow center. Thus, the southern half of the Moon will appear much darker than the northern half because it lies deeper in the umbra. Since the Moon samples a large range of umbral depths during totality, its appearance will change dramatically with time. It is not possible to predict the exact brightness distribution in the umbra, so observers are encouraged to estimate the Danjon value at different times during totality (see Danjon Scale of Lunar Eclipse Brightness). Note that it may also be necessary to assign different Danjon values to different portions of the Moon (i.e., north vs. south)."

And if want to visualize the sun-earth-geometry find here a computer animation I did a few years ago.

Enjoy la bella luna!

Moon at Sun Farm