Editing Saros (astronomy) (section)

== Saros series ==
[[File:Saros 136 animation.gif|thumb|left|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, while solar eclipses occurring near the Moon's ascending node are given ''odd'' saros series numbers. The first eclipse of each series starts at the northern limb of the Earth and the eclipse's path is shifted southward with each successive saros.]]

Each saros series starts with a partial eclipse (Sun first enters the end of the node), and each successive saros the path of the Moon is shifted either northward (when near the descending node) or southward (when near the ascending node) due to the fact that the saros is not an exact integer of draconic months (about one hour short). At some point, eclipses are no longer possible and the series terminates (Sun leaves the beginning of the node). An arbitrary solar saros series was designated as solar saros series 1 by compilers of eclipse statistics. This series has finished, but the eclipse of November 16, 1990 BC ([[Julian calendar]]) for example is in solar saros series 1. There are different saros series for solar and lunar eclipses. For lunar saros series, the lunar eclipse occurring 58.5 synodic months earlier (February 23, 1994 BC) was assigned the number 1. If there is an eclipse one [[inex]] (29 years minus about 20 days) after an eclipse of a particular saros series then it is a member of the next series. For example, the eclipse of October 26, 1961 BC is in solar saros series 2. Saros series, of course, went on before these dates, and it is necessary to extend the saros series numbers backwards to negative numbers even just to accommodate eclipses occurring in the years following 2000 BC (up till the last eclipse with a negative saros number in 1367 BC). For solar eclipses the statistics for the complete saros series within the era between 2000 BC and AD 3000 are given in this article's references.<ref name="Meeus-Mathematical Astronomy Morsels III">{{cite book|last=Meeus|first=Jean|date=2004|title=Ch. 18 "About Saros and Inex series" in: Mathematical Astronomy Morsels III|publisher=Willmann-Bell, Richmond VA, USA}}</ref><ref name="Espenak-Five Millennium Canon of Solar Eclipses">{{cite web|last=Espenak|first=Fred|author2=Jean Meeus|title=Five Millennium Canon of Solar Eclipses, Section 4 (NASA TP-2006-214141)|publisher=NASA STI Program Office|date=October 2006|url=http://sunearth.gsfc.nasa.gov/eclipse/5MCSE/5MCSE-Text.pdf|access-date=2007-01-24|url-status=dead|archive-url=https://web.archive.org/web/20070620150046/http://sunearth.gsfc.nasa.gov/eclipse/5MCSE/5MCSE-Text.pdf|archive-date=2007-06-20}}</ref> 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, as mentioned, are numbered according to the type of eclipse (lunar or solar).<ref>{{cite book|author=G. van den Bergh|date=1955|title=Periodicity and Variation of Solar (and Lunar) Eclipses (2 vols.)|publisher=H. D. Tjeenk Willink & Zoon N. V., Haarlem}}</ref><ref>{{cite book|author=Bao-Lin Liu|author2=Alan D. Fiala|date=1992|title=Canon of Lunar Eclipses, 1500 B.C. to A.D. 3000|publisher=Willmann-Bell, Richmond VA}}</ref> In odd numbered series (for solar eclipses) the Sun is near the ascending node, whereas in even numbered series it is near the descending node (this is reversed for lunar eclipse saros series). Generally, the ordering of these series determines the time at which each series peaks, which corresponds to when an eclipse is closest to one of the lunar nodes. For solar eclipses, the 40 series numbered between [[Solar Saros 117|117]] and [[Solar Saros 156|156]] are active (series 117 will end in 2054), whereas for lunar eclipses, there are now 41 active saros series (these numbers can be derived by counting the number of eclipses listed over an 18-year (saros) period from the eclipse catalog sites).<ref name="NASA Solar eclipses">{{Cite web|url=https://eclipse.gsfc.nasa.gov/SEdecade/SEdecade2011.html|title=NASA - Solar Eclipses: 2011 - 2020|website=eclipse.gsfc.nasa.gov}}</ref><ref name="NASA lunar eclipses">{{Cite web|url=https://eclipse.gsfc.nasa.gov/LEdecade/LEdecade2011.html|title=NASA - Lunar Eclipses: 2011 - 2020|website=eclipse.gsfc.nasa.gov}}</ref>

===Example===
{|class="wikitable collapsible" align="right" style="width:350; font-size:90%; margin-left:20px;"
|+ class="nowrap" | Saros 131 lunar eclipse dates
|May 10, 1427<br/>([[Julian calendar]]) || '''First penumbral''' <br/>(southern edge of shadow)
|-
|colspan="2" align="center" | ''...6 intervening penumbral eclipses omitted...''
|-
| July 25, 1553<br/>(Julian calendar) || '''First partial'''
|-
|colspan="2" align="center" | ''...19 intervening partial eclipses omitted...''
|-
| [[March 1932 lunar eclipse|March 22, 1932]]<br/>'''Final partial''' || 12:32 UT
|-
| [[April 1950 lunar eclipse|April 2, 1950]]<br/>'''First total''' || 20:44 UT [[File:Lunar eclipse chart close-1950Apr02.png|80px]]
|-
| [[April 1968 lunar eclipse|April 13, 1968]] || 04:47 UT
|-
| [[April 1986 lunar eclipse|April 24, 1986]] || 12:43 UT
|-
| [[May 2004 lunar eclipse|May 4, 2004]] || 20:30 UT
|-
| [[May 2022 lunar eclipse|May 16, 2022]]<br/>'''First central'''|| 04:11 UT [[File:Lunar eclipse chart close-2022may16.png|80px]]
|-
| [[May 2040 lunar eclipse|May 26, 2040]] || 11:45 UT
|-
| [[June 2058 lunar eclipse|June 6, 2058]] || 19:14 UT
|-
| [[June 2076 lunar eclipse|June 17, 2076]]<br/>'''Central''' || 02:37 UT [[File:Lunar eclipse chart close-2076Jun17.png|80px]]
|-
| colspan=2 align="center" | ...6 intervening total eclipses omitted...
|-
| September 3, 2202<br/>'''Last total'''|| 05:59 UT
|-
| September 13, 2220<br/> || '''First partial'''
|-
| colspan=2 align="center" | ''...18 intervening partial eclipses omitted...''
|-
| April 9, 2563 || '''Last partial umbral'''
|-
| colspan=2 align="center" |''...7 intervening penumbral eclipses omitted...''
|-
| July 7, 2707 || '''Last penumbral'''<br/> (northern edge of shadow)
|}

As an example of a single saros series, this 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. In each successive saros, 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 in 2078. The first partial eclipse after this will occur in the year 2220, and the final partial eclipse of the series will occur in 2707. The total lifetime of lunar saros series 131 is 1280 years. [[Solar Saros 138|Solar saros 138]] interleaves with this lunar saros with an event occurring every 9 years 5 days alternating between each saros series.

Because of the {{frac||1|3}} fraction of days in a saros, 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 about 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 about 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 start to the end of the series, with minor variations. [[Solar Saros 138|Solar saros 138]] interleaves with this lunar saros with an event occurring every 9 years 5 days alternating between each saros series.

For a similar example for solar saros see [[solar saros 136]].