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What's Up in the Sky for November 2010

posted Nov 1, 2010, 10:31 AM by Marvin Stewart   [ updated Nov 5, 2010, 2:23 PM by James Roe ]
What's Up In The Sky, November 2010    
             
           On December 21, 2010, there will be a total lunar eclipse. This eclipse, visible in North America, is number 48 of a series of Lunar eclipses belonging to Saros 125 that began as penumbral eclipse over the North Pole on July 17, 1163 AD.  Let me attempt to explain.  In ancient Chaldea, which existed from 625 - 539 BC in the area of what is today modern Iraq and Kuwait, there was an astronomer, Suadis. Suadis figured out that eclipses occur in cycles of 18 years, 10 to 11 days (depending if it is a leap year or not ) and 8 hours. Or to put it another way every 6,585.3 days. Not bad for someone that didn't know as much about astronomy as an advanced member of our astronomy club and we have computers.
          If the Earth wasn't tilted on its axis and the Moon followed the Ecliptic, every new Moon would produce a solar eclipse and every full Moon there would be a lunar eclipse. Since the Earth has a 23.3 tilt and the Moon doesn't travel around our equator but is tilted about 5 degrees to it, we get into position for eclipses four times a year, although it is possible to have five, and they are special.
         Sir Edmund Halley gave the eclipse cycle the name Saros in 1691.  In 1955 a Dutch astronomer, George van den Bergh, sorted out and numbered 8,000 eclipses and placed them in what he called a Canon.  After putting all this together, we come to what I know. A Saros cycle is called descending if it began at the North Pole and ascending if the cycle started at the South Pole, each cycle ends at the opposite pole.  A cycle can last  twelve to fifteen centuries and can have seventy or more events. Solar eclipse cycles are even numbered if they are descending, odd numbered if they are ascending. Lunar eclipse cycles are odd numbered if they are descending and even numbered if ascending. Simply put the Lunar cycles are numbered the opposite of the Solar cycles. At any one time a number of cycles can be going on simultaneously. At present there are 41 lunar cycles and 39 solar series active.
        Which brings me back to the December 21 eclipse. It is Saros 125, which began July 17, 1163, as a penumbral eclipse, with Earth's shadow just touching the southern part of the Moon. This eclipse was visible from our most northern lattitudes. 18 years 10 - 11 days later once again the Sun, and Moon were in the exact same position they were to create the last eclipse but the 8 hours has caused the Earth to rotate about 1/3 of a day further. This put the starting point of the second eclipse in another place on the Earth. Although it too was a penumbral eclipse, the Earth's shadow was slightly further north on the face of the Moon and it was also bigger. And, so it goes with each cycle, the Earth's shadow on the Moon moving north, the shadow getting bigger and darker, and the eclipse lasting longer.
        So far Saros 125 has produced 17 penumbral eclipses, 13 partial, and the Dec.  21st  event will be the eighteenth total eclipse with 8 more to go. Then the Earth's shadow will slowly slip up the face of the Moon to produce 9 more partial and 7 last penumbral, the very last the seventy second of the series, being over our South Pole on September 9, 2443.
 
        Nov  4  The Moon passes 2 degrees south of the planet Saturn.
                 6  New Moon.
               13  First quarter Moon.
               14  Neptune 5 deg south of the Moon.
               15  Mercury passes 2 deg. north of Antares
               17  Leonid meteor shower, best time after 3 am when Moon is set.
               20  Mercury and Mars in close approach in the evening sky, the closest of the year.
               21  Full Moon.
               28  last quarter Moon.
              
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