|28 Dec 2003 @ 22:50, by John Ashbaugh|
The planet turns through its Saros,
And the eclipse of the sun returns
to not exactly but near enough to
where it was fifty-four years before.
From a place near the center of the great continent of Africa-Eurasia,
to a third of a way around the globe
eighteen years later,
to a place another third of the way around the globe
another eighteen years later,
to another place in north Africa
near its previous visit,
eighteen years later.
From ancient times, lunar and solar eclipses have been regarded both as signs of awe and fear or of beauty and amazement. It is therefore understandable that astronomers have continuously searched for methods of predicting their occurrence and circumstances.
The Saros cycle is a successful eclipse series as its period of 223 synodic months not only closely approximates 242 draconic months but also because the number of anomalistic returns of the Sun (18.029) and the Moon (238.992) are nearly whole numbers. Successive eclipses in a Saros series are therefore very similar in character. The main drawback of the cycles lies in the fact that after each eclipse the time of maximum obscuration is shifted by nearly 8 hours so that successive eclipses are about 120º apart in longitude and thus often not visible from a fixed position on Earth.
Solar eclipses in an odd-numbered Saros series occur near the ascending node of the lunar orbit: they start with a small partial eclipse in the northern polar regions and slowly progress southwards, ending with a small partial eclipse in the southern polar regions. Solar eclipses in an even-numbered Saros series occur near the descending node of the lunar orbit: they start with a small partial eclipse in the southern polar regions and slowly progress northwards, ending with a small partial eclipse in the northern polar regions.
Solar Saros series can be as short as 1226 years (with 69 members) and as long as 1532 years (with 86 members). An average solar Saros series lasts about 1370 years and contains about 77 members of which some 48 are central. At the moment 39 solar Saros series are active (nrs. 117 to 155). A new series (nr. 156) will commence on 1 July 2011 after which 40 solar Saros series will be active until 3 August 2054 with the demise of series nr. 117.
This page contains info on various astronomical subjects related primarily to the study of Mesoamerica.
"Welcome to the Eclipse Home Page at the NASA/GSFC Sun-Earth Connection Education Forum. This web site is continually expanding and strives to be the ultimate resource for online information about eclipses.
The Mesopotamians, and in particular the Babylonians, were one of the first civilisations to keep records of their astronomical observations. Because of this, they were also the first to notice a remarkable pattern: that eclipses of a particular type are repeated every 18 years, and more closely repeated every 54 years. If they saw a total eclipse followed some six months later by a small partial eclipse, then just over eighteen years later they would see another total eclipse followed by a small partial eclipse.The 18 year period became known as the Saros, and the 54 year one as the Triple Saros or Exeligmos.
29 Dec 2003 @ 05:55 by swan : Thank you, John
for the information and links on eclipses. I have always found them fascinating and beautiful and they have been subjects metaphorically in my poetry and my painting.
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