Total Lunar Eclipse starts Saturday at 2:30 in the morning Dec. 10, greatest at 5:30 a.m.
Lunar Eclipse Dec. 10, 2011, starts around 2:30 a.m. Alaska Time, with total eclipse from 5 a.m. to 6 a.m.
Editor's Note: Alaska is 9 hours earlier than UT time. So the greatest eclipse, shown at 14:31:49 UT Saturday, Dec. 10, will be 5:31 a.m. Alaska Time, Saturday morning. Here's another NASA link for interactive watching of the eclipse and more info.
The last eclipse of 2011 is a total lunar eclipse that takes place at the Moon's descending node in eastern Taurus, four days after apogee.
The Moon's orbital trajectory takes it through the southern half of Earth's umbral shadow. Although the eclipse is not central, the total phase still lasts 51 minutes. The Moon's path through Earth's shadows as well as a map illustrating worldwide visibility of the event are shown in Figure 6. The timings of the major eclipse phases are listed below.
Penumbral Eclipse Begins: 11:33:32 UT Partial Eclipse Begins: 12:45:42 UT Total Eclipse Begins: 14:06:16 UT Greatest Eclipse: 14:31:49 UT Total Eclipse Ends: 14:57:24 UT Partial Eclipse Ends: 16:17:58 UT Penumbral Eclipse Ends: 17:30:00 UT
At the instant of greatest eclipse (14:32 UT) the Moon lies at the zenith in the Pacific Ocean near Guam and the Northern Mariana Islands. The umbral eclipse magnitude peaks at 1.1061 as the Moon's centre passes 21.4 arc-minutes south of the shadow axis. The Moon's northern limb is then 6.4 arc-minutes south of the shadows axis and 33.3 arc-minutes from the umbra's edge. In contrast, the Moon's southern limb lays 36.5 arc-minutes from the shadow centre and 3.2 arc-minutes from the southern edge of the umbra. Thus, the northern half of the Moon will appear much darker than the southern 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 difficult to predict the 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).
During totality, the winter constellations are well placed for viewing so a number of bright stars can be used for magnitude comparisons. Aldebaran (mv = +0.87) is 9° to the southwest of the eclipsed Moon, while Betelgeuse (mv = +0.45) is 19° to the southeast, Pollux (mv = +1.16) is 37° east, and Capella (mv = +0.08) is 24° north.
Table 6 lists predicted umbral immersion and emersion times for 20 well-defined lunar craters. The timing of craters is useful in determining the atmospheric enlargement of Earth's shadow (see Crater Timings During Lunar Eclipses).
The December 10 total lunar eclipse is the 23rd member of Saros 135, a series of 71 eclipses occurring in the following order: 9 penumbral, 10 partial, 23 total, 7 partial, and 22 penumbral lunar eclipses. Complete details for Saros 135 can be found at:
Eclipse Altitudes and Azimuths
The altitude a and azimuth A of the Sun or Moon during an eclipse depend on the time and the observer's geographic coordinates. They are calculated as follows:
h = 15 (GST + UT - α ) + λ a = arcsin [sin δ sin φ + cos δ cos h cos φ] A = arctan [-(cos δ sin h)/(sin δ cos φ - cos δ cos h sin φ)] where h = hour angle of Sun or Moon a = altitude A = azimuth GST = Greenwich Sidereal Time at 0:00 UT UT = Universal Time α = right ascension of Sun or Moon δ = declination of Sun or Moon λ = observer's longitude (east +, west -) φ = observer's latitude (north +, south -)
During the eclipses of 2011, the values for GST and the geocentric Right Ascension and Declination of the Sun or the Moon (at greatest eclipse) are as follows:
Eclipse Date GST α δ Partial Solar 2011 Jan 04 6.884 18.987 -22.739 Partial Solar 2011 Jun 01 16.609 4.631 22.096 Total Lunar 2011 Jun 15 17.584 17.592 -23.231 Partial Solar 2011 Jul 01 18.580 6.667 23.118 Partial Solar 2011 Nov 25 4.239 16.037 -20.682 Total Lunar 2011 Dec 10 5.265 5.143 22.554
Eclipses During 2012
During 2012, there will be two solar eclipses and two lunar eclipses:
- 2012 May 20: Annular Solar Eclipse
- 2012 Jun 04: Partial Lunar Eclipse
- 2012 Nov 13: Total Solar Eclipse
- 2012 Nov 28: Penumbral Lunar Eclipse
A full report on eclipses during 2012 will be published in Observer's Handbook 2012.
Eclipse Web Sites
The NASA Eclipse Web Site features predictions and maps for all solar and lunar eclipses throughout the 21st century, with special emphasis on upcoming eclipses. Special pages devoted to the total and annular solar eclipses of 2012 will feature detailed maps, tables, graphs, and meteorological data. A world atlas of solar eclipses provides maps of all central eclipse paths from 2000 BCE to 3000 CE. The entire Five Millennium Canon of Solar Eclipses (Espenak and Meeus, 2006) and Five Millennium Canon of Lunar Eclipses (Espenak and Meeus, 2009a) can be downloaded in PDF format and all figures are also available online as individual GIFs. On-line versions of the entire Five Millennium Catalog of Solar Eclipses (Espenak and Meeus, 2009c) and Five Millennium Catalog of Lunar Eclipses (Espenak and Meeus, 2009b) list details for every solar and lunar eclipse over the same 5000-year period. The NASA Eclipse Web Site is located at:
Detailed information on solar and lunar eclipse photography, and tips on eclipse observing and eye safety may be found at:
All eclipse predictions were generated on an Apple G4 iMac computer using algorithms developed from the Explanatory Supplement  with additional algorithms from Meeus, Grosjean, and Vanderleen . The solar coordinates used in the eclipse predictions are based on VSOP87 [P. Bretagnon and G. Francou, 1988]. The lunar coordinates are based on ELP-2000/82 [M. Chapront-Touzé and J. Chapront, 1983]. For lunar eclipses, the diameter of the umbral and penumbral shadows were calculated using Danjon's rule of enlarging Earth's radius by 1/85 to compensate for the opacity of the terrestrial atmosphere; corrections for the effects of oblateness have also been included. Text and table composition was done on a Macintosh using Microsoft Word. Additional figure annotation was performed with Claris MacDraw Pro.
All calculations, diagrams, tables, and opinions presented in this paper are those of the author, and he assumes full responsibility for their accuracy.
 Eclipse magnitude for solar eclipses is defined as the fraction of the Sun's diameter occulted by the Moon.
 The instant of greatest eclipse for solar eclipses occurs when the distance between the Moon's shadow axis and Earth's geocentre reaches a minimum.
 Eclipse obscuration is defined as the fraction of the Sun's area occulted by the Moon.
 The Saros is a period of 6,585.3 days (18 years 11 days 8 hours) in which eclipses (both solar and lunar) repeat. The geometry isn't exact but close enough for a Saros series to last 12 or more centuries.
 The instant of greatest eclipse for lunar eclipses occurs when the distance between the Moon's shadow axis and Earth's geocentre reaches a minimum.
 Umbral eclipse magnitude is defined as the fraction of the Moon's diameter occulted by the umbral shadow.
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SOOURCE: NASA Eclipse Web Site http://eclipse.gsfc.nasa.gov/eclipse.html