Senin, 12 Desember 2011

ECLIPSES DURING 2012



NASA Eclipse Web SiteTwo solar and two lunar eclipses take place in 2012 as follows.
2012 May 20: Annular Solar Eclipse
2012 Jun 04: Partial Lunar Eclipse
2012 Nov 13: Total Solar Eclipse
2012 Nov 28: Penumbral Lunar Eclipse
Predictions for the eclipses are summarized in Figures 1, 2, 3, 4. 5, and 6. World maps show the regions of visibility for each eclipse. The lunar eclipse diagrams also include the path of the Moon through Earth's shadows. Contact times for each principal phase are tabulated along with the magnitudes and geocentric coordinates of the Sun and Moon at greatest eclipse.
All times and dates used in this publication are in Universal Time or UT. This astronomically derived time system is colloquially referred to as Greenwich Mean Time or GMT. To learn more about UT and how to convert UT to your own local time, see Time Zones and Universal Time.

Annular Solar Eclipse of May 20

The first solar eclipse of 2012 occurs at the Moon's descending node in central Taurus. An annular eclipse will be visible from a 240 to 300 kilometre-wide track that traverses eastern Asia, the northern Pacific Ocean and the western United States. A partial eclipse is seen within the much broader path of the Moon's penumbral shadow, that includes much of Asia, the Pacific and the western 2/3 of North America (Figure 1).
The annular path begins in southern China at 22:06 UT. Because the Moon passed through apogee one day earlier (May 19 at 16:14 UT), its large distance from Earth produces a wide path of annularity. Traveling eastward, the shadow quickly sweeps along the southern coast of Japan as the central line duration of annularity grows from 4.4 to 5.0 minutes.
Tokyo lies 10 kilometres north of the central line. For the over 10 million residents within the metropolitan area, the annular phase will last 5 minutes beginning at 22:32 UT (on May 21 local time). The annular ring is quite thick because the Moon's apparent diameter is only 94% that of the Sun. Traveling with a velocity of 1.1 kilometres/second, the antumbral shadow leaves Japan and heads northeast across the Northern Pacific. The instant of greatest eclipse [1] occurs at 23:52:47 UT when the eclipse magnitude [2] reaches 0.9439. At that instant, the duration of annularity is 5 minutes 46 seconds, the path width is 237 kilometres and the Sun is 61° above the flat horizon formed by the open ocean.
The shadow passes just south of Alaska's Aleutian Islands as the central track slowly curves to the southeast. After a 7000 kilometre-long ocean voyage lasting nearly 2 hours, the antumbra finally reaches land again along the rugged coastlines of southern Oregon and northern California (Figure 2) at 01:23 UT (May 20 local time).
Redding, CA lies 30 kilometres south of the central line. Nevertheless, it still experiences an annular phase lasting 4 1/2 minutes beginning at 01:26 UT. It is already late afternoon along this section of the eclipse path. The Sun's altitude is 20° during the annular phase and decreasing as the track heads southeast. Central Nevada, southern Utah, and northern Arizona are all within the annular path.
By the time the antumbra reaches Albuquerque, NM (01:34 UT), the central duration is still 4 1/2 minutes, but the Sun's altitude has dropped to 5°. As its leading edge reaches the Texas Panhandle, the shadow is now an elongated ellipse extending all the way to Nevada. Seconds later, the antumbra begins its rise back into space above western Texas as the track and the annular eclipse end.
During the course of its 3.5-hour trajectory, the antumbra's track is approximately 13,600 kilometres long and covers 0.74% of Earth's surface area. Path coordinates and central line circumstances are presented in Table 1.
Partial phases of the eclipse are visible primarily from the USA, Canada, the Pacific and East Asia. Local circumstances for a number of cities are found in Table 2 (USA) and Table 3 (Canada, Mexico and Asia). All times are given in Universal Time. The Sun's altitude and azimuth, the eclipse magnitude and obscuration are all given at the instant of maximum eclipse.
The NASA JavaScript Solar Eclipse Explorer is an interactive web page that can quickly calculate the local circumstances of the eclipse from any geographic location not included in Table 1:
This is the 33rd eclipse of Saros 128 (Espenak and Meeus, 2006). The family began with a series of 24 partial eclipses starting on 0984 Aug 29. The first central eclipse was total and took place on 1417 May 16. After three more totals and four hybrid eclipses, the series changed to annular on 1561 Aug 11. Subsequent members of Saros 128 were all annular eclipses with increasing durations, the maximum of which was reached on 1832 Feb 01 and lasted 08 minutes 35 seconds. The duration of annularity of each succeeding eclipse is now dropping and will reach 4 minutes with the last annular eclipse of the series on 2120 Jul 25. Saros 128 terminates on 2282 Nov 01 after a string of 9 partial eclipses. Complete details for the 73 eclipses in the series (in the sequence of 24 partial, 4 total, 4 hybrid, 32 annular, and 9 partial) may be found at:
Additional details for the 2012 annular solar eclipse (including tables, maps and weather prospects) can be found at:

Partial Lunar Eclipse of June 04

The first lunar eclipse of 2012 occurs at the Moon's ascending node in southern Ophiuchus about 6° northeast of Antares (mv = +1.07). It is best seen from locations in and near the Pacific Ocean (Figure 3). Most of the Americas will experience moonset before the eclipse ends while eastern Asia will miss the beginning of the eclipse because it occurs before moonrise. The Moon's contact times with Earth's shadows are listed below.
Penumbral Eclipse Begins:    08:48:09 UT
                 Partial Eclipse Begins:      09:59:53 UT
                 Greatest Eclipse:            11:03:13 UT
                 Partial Eclipse Ends:        12:06:30 UT
                 Penumbral Eclipse Ends:      13:18:17 UT
At the instant of greatest eclipse the umbral eclipse magnitude will reach 0.3705. At that time the Moon will be at the zenith for observers in the South Pacific. In spite of the fact that just a third of the Moon enters the umbral shadow (the Moon's southern limb dips 12.3 arc-minutes into the umbra), the partial phase still lasts over 2 hours.
Figure 3 shows the path of the Moon through the penumbra and umbra as well as a map of Earth showing the regions of eclipse visibility. New England and eastern Canada will miss the entire eclipse since the event begins after moonset from those regions. Observers in western Canada and the USA will have the best views with moonset occurring sometime after mid-eclipse. To catch the entire event, one must be located in the Pacific or eastern Australia.
The June 04 partial lunar eclipse belongs to Saros 140, a series of 77 eclipses in the following sequence: 20 penumbral, 8 partial, 28 total, 7 partial, and 14 penumbral lunar eclipses (Espenak and Meeus, 2009). Complete details for the series can be found at:

Total Solar Eclipse of November 13

The second solar eclipse of 2012 occurs at the Moon's ascending node in central Libra. The path of the Moon's umbral shadow crosses the South Pacific Ocean where it makes no landfall except for northern Australia. The Moon's penumbral shadow produces a partial eclipse visible from a much larger region covering the South Pacific (including Australia and New Zealand), southern South America, and part of Antarctica (Figure 4).
The central eclipse path begins in Australia's Garig Ganak Barlu National Park in the Northern Territory about 250 kilometres east of Darwin at 20:35 UT (Figure 5). Traveling southeast, the umbral shadow quickly crosses the Gulf of Carpentaria and reaches the Cape York Peninsula at 20:37 UT.
The first and only populated region in the path lies along the east coast of Queensland. Gateway to Australia's Great Barrier Reef, Cairns is about 30 kilometres south of the central line. Its residents and visitors will enjoy an early morning total eclipse lasting 2 minutes with the Sun just 14° above the eastern horizon. Observers on the central line can eek out another 5 seconds of totality, but local weather conditions will play a far greater role in choosing a viewing site than a few seconds of totality.
After leaving Australia, the umbral shadow glides over the ocean, undisturbed by further landfall for the remainder of its track. Greatest eclipse occurs in the South Pacific at 22:11:48 UT. At this instant, the axis of the Moon's shadow passes closest to Earth's centre. The maximum duration of totality is 4 minutes 2 seconds, the Sun's altitude is 68°, and the path width is 179 kilometres. Continuing across the vast South Pacific, the umbral shadow's path ends about 800 kilometres west of Chile at 23:48 UT.
The NASA JavaScript Solar Eclipse Explorer is an interactive web page that can quickly calculate the local circumstances of the eclipse from any geographic location within the eclipse path:
Over the course of 3.1 hours, the Moon's umbra travels along a path approximately 14,500 kilometres long covering 0.46% of Earth's surface area. Path coordinates and central line circumstances are presented in Table 4. All times are given in Universal Time. The Sun's altitude and azimuth, the eclipse magnitude and obscuration are all given at the instant of maximum eclipse.
This is the 45th eclipse of Saros 133 (Espenak and Meeus, 2006). The series began on 1219 Jul 13 with the first of 13 partial eclipses. The first annular eclipse was non-central and occurred on 1435 Nov 20. Five more annular eclipses followed until a hybrid eclipse on 1544 Jan 24. Subsequent eclipses in the series have been total with a steadily increasing duration of totality until the peak duration of 6 minutes 50 seconds was reached on 1850 Aug 07. The duration of totality has been decreasing since then. The remaining 20 total eclipses will see totality drop to below 2 minutes. The series ends with a set of 7 partial eclipses the last of which occurs on 2499 Sep 05.
In all, Saros 133 produces 12 partial, 6 annular, 1 hybrid, 46 total, and 24 partial eclipses, in that order. Complete details for the series can be found at:
Additional details for the 2012 total solar eclipse (including tables, maps and weather prospects) can be found at:

Penumbral Lunar Eclipse of November 28

The last lunar eclipse of 2012 is a deep penumbral eclipse with a magnitude of 0.9155. It should be easily visible to the naked eye as a dusky shading in the northern half of the Moon. The times of the major phases are listed below.
Penumbral Eclipse Begins:    12:14:58 UT
                 Greatest Eclipse:            14:33:00 UT
                 Penumbral Eclipse Ends:      16:51:02 UT
Note that the beginning and end of a penumbral eclipse are not visible to the eye. In fact, no shading can be detected until about 2/3 of the Moon's disk is immersed in the penumbra. This would put the period of eclipse visibility from approximately 14:00 to 15:00 UT. Keep in mind that this is only an estimate. Atmospheric conditions and the observer's visual acuity are important factors to consider. An interesting exercise is to note when penumbral shading is first and last seen.
Figure 6 shows the path of the Moon through the penumbra as well as a map of Earth showing the regions of eclipse visibility. Eastern Canada and the USA will miss the eclipse entirely since it begins after moonset. Observers in western Canada and the USA will have the best views with moonset occurring sometime after mid-eclipse. To catch the entire event, one must be in Alaska, Hawaii, Australia, or East Asia.
The November 28 penumbral lunar eclipse is the 11th member of Saros 145, a series of 71 eclipses in the following sequence: 18 penumbral, 10 partial, 15 total, 20 partial, and 8 penumbral lunar eclipses (Espenak and Meeus, 2009). Complete details for the series can be found at:

Explanatory Information

Solar Eclipse Figures

Lunar Eclipse Figures

Shadow Diameters and Lunar Eclipses

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 2012, 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

Annular Solar    2012 May 20    15.935     3.879    20.221
Partial Lunar    2012 Jun 04    16.886    16.860   -21.666
Total Solar      2012 Nov 13     3.561    15.302   -18.251
Penumbral Lunar  2012 Nov 28     4.526     4.334    20.462
Two web based tools that can also be used to calculate the local circumstances for all solar and lunar eclipses visible from any location. They are the Javascript Solar Eclipse Explorer and the Javascript Lunar Eclipse Explorer. The URLs for these tools are:
Javascript Solar Eclipse Explorer: eclipse.gsfc.nasa.gov/JSEX/JSEX-index.html
Javascript Lunar Eclipse Explorer: eclipse.gsfc.nasa.gov/JLEX/JLEX-index.html

Eclipses During 2013

During the year 2013, two solar and three lunar eclipses occur as follows:
A full report on eclipses during 2013 will be published in Observer's Handbook 2013.

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:

Acknowledgments

All eclipse predictions were generated on an Apple Power Mac G4 computer using algorithms developed from the Explanatory Supplement [1974] with additional algorithms from Meeus, Grosjean, and Vanderleen [1966]. 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.

Footnotes

[1] Eclipse magnitude for solar eclipses is defined as the fraction of the Sun's diameter occulted by the Moon.
[2] 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.
[3] Eclipse obscuration is defined as the fraction of the Sun's area occulted by the Moon.
[4] 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.
[5] 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.
[6] Umbral eclipse magnitude is defined as the fraction of the Moon's diameter occulted by the umbral shadow.

Reference
http://eclipse.gsfc.nasa.gov/OH/OH2012.html#SE2012May20A




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