The origin of the Saros cycle comes from the recognition that 223 synodic months is approximately equal to 242 draconic months which is approximately equal to 239 anomalistic months (this approximation is good to within about 2 hours). After one Saros cycle the Moon will have completed roughly an integer number of synodic draconic and anomalistic months and the Earth-Sun-Moon geometry will be nearly identical: the Moon will have the same phase be at the same node and have the same distance from the Earth. If one knew the date of an eclipse then one Saros later a nearly identical eclipse should occur. Mind that during that 18 year cycle about 40 other solar and lunar eclipses take place but with a somewhat different geometry. Note also that the Saros cycle (18.031 years) is not equal to an integer number of revolutions of the Moon with respect to the fixed stars (sidereal month of 27.32 days). Therefore even though the relative geometry of the Earth-Sun-Moon system will be nearly identical after a Saros the Moon will be in a different position with respect to the stars. This is due to the fact that the orbit of the Moon precesses.

A complication with the Saros cycle is that its period is not an integer number of days but contains a multiple of of a day. Thus as a result of the Earth's rotation for each successive Saros cycle an eclipse will occur about 8 hours later in the day. In the case of an eclipse of the Sun this means that the region of visibility will shift westward by 120 or one third of the way around the globe and the two eclipses will thus not be visible from the same place on Earth. In the case of an eclipse of the Moon the next eclipse might still be visible from the same location as long as the Moon is above the horizon. However if one waits three Saros cycles the local time of day of an eclipse will be nearly the same. This period of three Saros cycles (54 years 1 month or almost 19756 full days) is known as a Triple Saros or exeligmos (Greek: "turn of the wheel"). Saros series Lunar eclipses occurring near the Moon's descending node are given odd Saros series numbers. The first eclipse in such series passes through the southern edge of the Earth's shadow and the Moon's path is shifted northward each successive Saros cycle. Solar eclipses occurring near the Moon's descending node are given even Saros series numbers. The first eclipse of each series starts at the southern limb of the Earth and the eclipse's path is shifted northward with each successive Saros cycle.

The Saros cycle is based on the recognition that 223 synodic months approximately equal to 242 draconic months and 239 anomalistic months. However as this relationship is not perfect the geometry of two eclipses separated by one Saros cycle will differ slightly. In particular the place where the Sun and Moon come in conjunction shifts westward by about 0.5 with respect to the Moon's nodes every Saros cycle and this gives rise to a series of eclipses called a Saros series that slowly change in appearance.

Each Saros series starts with a partial eclipse (Sun first enters the end of the node) and each successive Saros cycle the path of the Moon is shifted either northward (when near the descending node) or southward (when near the ascending node). At some point eclipses are no longer possible and the series terminates (Sun leaves the beginning of the node). Arbitrary dates were established by compilers of eclipse statistics. These extreme dates are 2000 BCE and 3000 CE. Saros series of course went on before and will continue after these dates. Since the first eclipse of 2000 BCE was not the first in its saros it is necessary to extend the saros series numbers backwards beyond 0 to negative numbers to accommodate eclipses occurring in the years following 2000 BCE. The saros -13 is the first saros to appear in these data. For solar eclipses the statistics for the complete Saros series within the era between 2000 BCE and 3000 CE are given in this article's references.89 It takes between 1226 and 1550 years for the members of a saros series to traverse the Earth's surface from north to south (or vice-versa). These extremes allow from 69 to 87 eclipses in each series (most series have 71 or 72 eclipses). From 39 to 59 (mostly about 43) eclipses in a given series will be central (that is total annular or hybrid annular-total). At any given time approximately 40 different Saros series will be in progress.

Saros series are numbered according to the type of eclipse (solar or lunar) and whether they occur at the Moon's ascending or descending node.1011 Odd numbers are used for solar eclipses occurring near the ascending node whereas even numbers are given to descending node solar eclipses. For lunar eclipses this numbering scheme is somewhat random. The ordering of these series is determined by the time at which each series peaks which corresponds to when an eclipse is closest to one of the lunar nodes. For solar eclipses (in 2003) the 39 series numbered between 117 and 155 are active whereas for lunar eclipses there are now 41 active Saros series.citation needed Example: Lunar Saros 131 Saros 131 lunar eclipse dates May 10 1427 (Julian calendar) First penumbral (southern edge of shadow) ...6 intervening penumbral eclipses omitted... July 25 1553 (Julian calendar) First partial ...19 intervening partial eclipses omitted... March 22 1932 Final partial 12:32 UT April 2 1950 First total 20:44 UT April 13 1968 04:47 UT April 24 1986 12:43 UT May 4 2004 20:30 UT May 16 2022 First central 04:11 UT May 26 2040 11:45 UT June 6 2058 19:14 UT June 17 2076 Central 02:37 UT ...6 intervening total eclipses omitted... September 3 2202 Last total 05:59 UT September 13 2220 First partial ...18 intervening partial eclipses omitted... April 9 2563 Last partial umbral ...7 intervening penumbral eclipses omitted... July 7 2707 Last penumbral (northern edge of shadow) As an example of a single Saros series the accompanying table gives the dates of some of the 72 lunar eclipses for Saros series 131. This eclipse series began in AD 1427 with a partial eclipse at the southern edge of the Earth's shadow when the Moon was close to its descending node. Each successive Saros cycle the Moon's orbital path is shifted northward with respect to the Earth's shadow with the first total eclipse occurring in 1950. For the following 252 years total eclipses occur with the central eclipse being predicted to occur in 2078. The first partial eclipse after this is predicted to occur in the year 2220 and the final partial eclipse of the series will occur in 2707. The total lifetime of the lunar Saros series 131 is 1280 years. Because of the fraction of days in a Saros cycle the visibility of each eclipse will differ for an observer at a given locale. For the lunar Saros series 131 the first total eclipse of 1950 had its best visibility for viewers in Eastern Europe and the Middle East because mid-eclipse was at 20:44 UT. The following eclipse in the series occurred approximately 8 hours later in the day with mid-eclipse at 4:47 UT and was best seen from North America and South America. The third total eclipse occurred approximately 8 hours later in the day than the second eclipse with mid-eclipse at 12:43 UT and had its best visibility for viewers in the Western Pacific East Asia Australia and New Zealand. This cycle of visibility repeats from the initiation to termination of the series with minor variations. For a similar example for solar saros see Solar Saros 136. See also List of Saros series for lunar eclipses Eclipse cycle Solar eclipse Lunar eclipse Metonic cycle References Cited references Tablets 1414 1415 1416 1417 1419 of: T.G. Pinches J.N. Strassmaier: Late Babylonian Astronomical and Related Texts. A.J. Sachs (ed.) Brown University Press 1955 A.J. Sachs & H. Hunger (1987..1996): Astronomical Diaries and Related Texts from Babylonia Vol.I..III. sterreichischen Akademie der Wissenschaften. ibid. H. Hunger (2001) Vol. V: Lunar and Planetary Texts P.J. Huber & S de Meis (2004): Babylonian Eclipse Observations from 750 BC to 1 BC par. 1.1. IsIAO/Mimesis Milano Naturalis Historia II.1056 Almagest IV.2 Microsoft Encarta College Dictionary 2001 The Suda entry is online here. Meeus Jean (2004). Ch. 18 "About Saros and Inex series" in: Mathematical Astronomy Morsels III. Willmann-Bell Richmond VA USA.  Espenak Fred; Jean Meeus (October 2006). "Five Millennium Canon of Solar Eclipses Section 4 (NASA TP-2006-214141)" (PDF). NASA STI Program Office. http://sunearth.gsfc.nasa.gov/eclipse/5MCSE/5MCSE-Text.pdf. Retrieved 2007-01-24.  G. van den Bergh (1955). Periodicity and Variation of Solar (and Lunar) Eclipses (2 vols.). H.D. Tjeenk Willink & Zoon N.V. Haarlem.  Bao-Lin Liu and Alan D. Fiala (1992). Canon of Lunar Eclipses 1500 B.C. to A.D. 3000. Willmann-Bell Richmond VA.  General references Jean Meeus and Hermann Mucke (1983) Canon of Lunar Eclipses. Astronomisches Bro Vienna Theodor von Oppolzer (1887). Canon der Finsternisse. Vienna Mathematical Astronomy Morsels Jean Meeus Willmann-Bell Inc. 1997 (Chapter 9 p. 51 Table 9.A Some eclipse Periodicities) External links NASA - Eclipses and the Saros NASA - Catalog of Lunar Eclipses in Saros 0 NASA - Lunar Eclipses of Saros Series 1 to 180 NASA - Solar Eclipses of Saros Series 0 to 180 NASA - Summary of Lunar Eclipses in Saros Series -20 to 183 NASA - Summary of Solar Eclipses in Saros Series -13 to 190 Search among the 11898 solar eclipses over five millennium and display interactive maps Search among the 12064 lunar eclipses over five millennium and display interactive maps Eclipses and the Saros Cycle Eclipse Search -- here one can search 5000 years of eclipse data by type magnitude Saros number or simply by year. Saros series 131 table v d eSolar eclipses Lists of eclipses Antiquity  20th century BC  19th century BC  18th century BC  17th century BC  16th century BC  15th century BC  14th century BC  13th century BC  12th century BC  11th century BC  10th century BC  9th century BC  8th century BC  7th century BC  6th century BC  5th century BC  4th century BC  3rd century BC  2nd century BC  1st century BC  1st century  2nd century  3rd century  4th century  5th century  6th century  7th century  8th century  9th century  10th century  11th century  12th century  13th century  14th century  15th century  16th century  17th century  18th century  19th century  20th century  21st century  22nd century  23rd century  24th century  25th century  26th century  27th century  28th century  29th century  30th century Eclipses seen from: China  the United Kingdom  Philippines Saros cycles: 110  111  112  113  114  115  116  117  118  119  120  121  122  123  124  125  126  127  128  129  130  131  132  133  134  135  136  137  138  139  140  141  142  143  144  145  146  147  148  149  150  151  152  153  154  155  156  157  158  159  160  161  162 Historical eclipses Mursili's eclipse (1312 BC)  Assyrian eclipse (763 BC)  Battle of Halys (585 BC)  Crucifixion darkness and eclipse Past Total/hybrid eclipses 1560 Aug 21  1598 Mar 7  1652 Apr 8  1654 Aug 12  1699 Sep 23  1715 May 3  1724 May 22  1766 Feb 9  1778 Jun 24  1780 Oct 27  1806 Jun 16  1816 Nov 19  1820 Sep 7  1824 Jun 26  1842 Jul 8  1851 Jul 28  1853 Nov 30  1857 Mar 25  1858 Sep 7  1860 Jul 18   1865 Apr 25  1867 Aug 29  1868 Aug 18  1869 Aug 7  1870 Dec 22  1871 Dec 12  1874 Apr 16  1875 Apr 6  1878 Jul 29  1882 May 17   1883 May 6   1885 Sep 8   1886 Aug 29   1887 Aug 19   1889 Jan 1  1889 Dec 22   1893 Apr 16   1896 Aug 9   1898 Jan 22   1900 May 28  1901 May 18  1903 Sep 21  1904 Sep 9  1905 Aug 30  1907 Jan 14  1908 Jan 3  1908 Dec 23  1909 Jun 17  1910 May 9  1911 Apr 28  1912 Apr 17  1912 Oct 10  1914 Aug 21  1916 Feb 3  1918 Jun 8  1919 May 29  1921 Oct 1  1922 Sep 21  1923 Sep 10  1925 Jan 24  1926 Jan 14  1927 Jun 29  1928 May 19  1929 May 9  1930 Apr 28  1930 Oct 21  1932 Aug 31  1934 Feb 14  1936 Jun 19  1937 Jun 8  1938 May 29  1939 Oct 12  1940 Oct 1  1941 Sep 21  1943 Feb 4  1944 Jan 25  1944 Jul 20  1945 Jul 9  1947 May 20  1948 Nov 1  1950 Sep 12  1952 Feb 25  1954 Jun 30  1955 Jun 20  1956 Jun 8  1957 Oct 23  1958 Oct 12  1959 Oct 2  1961 Feb 15  1962 Feb 5  1963 Jul 20  1965 May 30  1966 Nov 12  1967 Nov 2  1968 Sep 22  1970 Mar 7  1972 Jul 10  1973 Jun 30  1974 Jun 20  1976 Oct 23  1977 Oct 12  1979 Feb 26  1980 Feb 16  1981 Jul 31  1983 Jun 11  1984 Nov 22  1985 Nov 12  1986 Oct 3  1987 Mar 29  1988 Mar 18  1990 Jul 22  1991 Jul 11  1992 Jun 30  1994 Nov 3  1995 Oct 24  1997 Mar 9  1998 Feb 26  1999 Aug 11  2001 Jun 21  2002 Dec 4  2003 Nov 23  2005 Apr 8  2006 Mar 29  2008 Aug 1  2009 Jul 22  2010 Jul 11 Future Total/hybrid eclipses 2012 Nov 13  2013 Nov 3  2015 Mar 20  2016 Mar 9  2017 Aug 21  2019 Jul 2  2020 Dec 14  2021 Dec 4  2023 Apr 20  2024 Apr 8  2026 Aug 12  2027 Aug 2  2028 Jul 22  2030 Nov 25  2031 Nov 14  2033 Mar 30  2034 Mar 20  2035 Sep 2  2037 Jul 13  2038 Dec 26  2039 Dec 15  2041 Apr 30  2042 Apr 20  2043 Apr 9  2044 Aug 23  2045 Aug 12  2046 Aug 2  2048 Dec 5  2049 Nov 25  2050 May 20  2052 Mar 30  2053 Sep 12  2055 Jul 24  2057 Jan 5  2057 Dec 26  2059 May 11  2060 Apr 30  2061 Apr 20  2063 Aug 24  2064 Aug 12  2066 Dec 17  2067 Dec 6  2068 May 31  2070 Apr 11  2071 Sep 23  2072 Sep 12  2073 Aug 3  2075 Jan 16  2076 Jan 6  2077 May 22  2078 May 11  2079 May 1  2081 Sep 3  2082 Aug 24  2084 Dec 27  2086 Jun 11  2088 Apr 21  2089 Oct 4  2090 Sep 23  2091 Aug 15  2093 Jan 27  2094 Jan 16  2095 Jun 2  2096 May 22  2097 May 11  2099 Sep 14  2100 Sep 4  2114 Jun 3  2132 Jun 13  2150 Jun 25  2168 Jul 5  2186 Jul 16 Past Annular eclipses 1854 May 26  1879 Jan 22  1889 Jun 28  1901 Nov 11  1903 Mar 29  1904 Mar 17  1905 Mar 6  1907 Jul 10  1908 Jun 28  1911 Oct 22  1914 Feb 25  1915 Feb 14  1915 Aug 10  1916 Jul 30  1917 Dec 14  1918 Dec 3  1919 Nov 22  1921 Apr 8  1922 Mar 28  1923 Mar 17  1925 Jul 20  1926 Jul 9  1927 Jan 3  1929 Nov 1  1932 Mar 7  1933 Feb 24  1933 Aug 21  1934 Aug 10  1935 Dec 25  1936 Dec 13  1937 Dec 2  1939 Apr 19  1940 Apr 7  1941 Mar 27  1943 Aug 1  1945 Jan 14  1947 Nov 12  1948 May 9  1950 Mar 18  1951 Mar 7  1951 Sep 1  1952 Aug 20  1954 Jan 5  1954 Dec 25  1955 Dec 14  1957 Apr 30  1958 Apr 19  1959 Apr 8  1961 Aug 11  1962 Jul 31  1963 Jan 25  1965 Nov 23  1966 May 20  1969 Mar 18  1969 Sep 11  1970 Aug 31  1972 Jan 16  1973 Jan 4  1973 Dec 24  1976 Apr 29  1977 Apr 18  1979 Aug 22  1980 Aug 10  1981 Feb 4  1983 Dec 4  1984 May 30  1987 Sep 23  1988 Sep 11  1990 Jan 26  1991 Jan 15  1992 Jan 4  1994 May 10  1995 Apr 29  1998 Aug 22  1999 Feb 16  2001 Dec 14  2002 Jun 10  2003 May 31  2005 Oct 3  2006 Sep 22  2008 Feb 7  2009 Jan 26  2010 Jan 15 Future Annular eclipses 2012 May 20  2013 May 10  2014 Apr 29  2016 Sep 1  2017 Feb 26  2019 Dec 26  2020 Jun 21  2021 Jun 10  2023 Oct 14  2024 Oct 2  2026 Feb 17  2027 Feb 6  2028 Jan 26  2030 Jun 1  2031 May 21  2032 May 9  2034 Sep 12  2035 Mar 9  2038 Jan 5  2038 Jul 2  2039 Jun 21  2041 Oct 25  2042 Oct 14  2043 Oct 3  2044 Feb 28  2045 Feb 16  2046 Feb 5  2048 Jun 11  2049 May 31  2052 Sep 22  2053 Mar 20  2056 Jan 16  2056 Jul 12  2057 Jul 1  2059 Nov 5  2060 Oct 24  2061 Oct 13  2063 Feb 28  2064 Feb 17  2066 Jun 22  2067 Jun 11  2070 Oct 4  2071 Mar 31  2074 Jan 27  2074 Jul 24  2075 Jul 13  2077 Nov 15  2078 Nov 4  2079 Oct 24  2081 Mar 10  2082 Feb 27  2084 Jul 3  2085 Jun 22  2085 Dec 16  2088 Oct 14  2089 Apr 10  2092 Feb 7  2092 Aug 3  2093 Jul 23  2095 Nov 27  2096 Nov 15  2097 Nov 4  2099 Mar 21  2100 Mar 10 Other planets Jupiter  Mars  Pluto Related topics Solar eclipses in fiction  Images