Can anyone help with this question? My question arose from an eclipse related observation that I made while looking into lunar Saros series 129. It is the Saros series number for the lunar eclipse that occurred on this past July 27, 2018.

First I saw that this Saros 129 series was "born" June 10, 1351 and the series will end June 24, 2613 (70 saros cycles of 18 years = roughly 1260 years). So, I became curious to see if another Saros series had ended just before Saros 129 began. I saw that Saros 89 (less by 40 in series numbering) had ended just four years earlier on July 23, 1347. Investigating further, I learned that there are roughly 40 different Saros series that are "active" at any one given time. So then I looked back further to lunar Saros 49 and observed that there does indeed seem to be a pattern involving roughly "40" less in the numbering (i.e. yes indeed, series 49 also ended just as series 89 began). These observations do seem to me as more than mere coincidences.

So, my question now is - Are these particular lunar Saros series (separated by "40" in numbering) related in any way? - series 49, 89, and 129. Is there another cycle or a "greater" cycle also at work here that I am unaware of?

Please see the comments below if what I am asking seems unclear - my comments might rephrase the question for clarity.

Edit - I checked several other Saros series numbers separated by 40. I am adding additional information below - hoping that it might help find an answer to this question about relatedness of the "40 apart" series.

Checking other series spaced by 40 numbering, these Saros series (that are numbered 40 apart – i.e. 40, 80, 120 etc.) always contain eclipses that are separated by ~1418 days between eclipses in each respective series (i.e. exactly 4 lunar years/48 lunar months).

Small Saros series (those containing fewer cycles - i.e. 70-74 saros cycles in the series) contain saros cycles that overlap minimally (Saros 129 which is only 70 eclipse cycles in length has no overlap and began just after Saros 89 came to an end 1418 days earlier). Note - zero eclipse cycles between them overlap.

Large Saros series (those containing more cycles – i.e. 80-84 saros cycles in the series) contain saros cycles that overlap accordingly (Saros 120 which is 83 cycles long thus began 13 cycles before Saros 80 came to an end with the overlapping eclipses each gapped by 1418 days). Note - 13 eclipse cycles overlap accordingly - again about 70 eclipse cycles with no overlap between these series.

It seems like about 70 eclipse cycles (constituting ~1262 solar years or ~1300 lunar years) is the standard length of each adjacent Saros series – considering the non-overlapping portion only – each non-overlapping portion separated by 4 lunar years.

Edit - Thanks to anyone who can shed any additional light on this.

Additional Edit - In response to the given answer concerning the "puzzling" 1418 days observed between every "standard saros series of 70 cycles", I have also noted that the observed "1418 day difference" between them appears to be the same difference that exists between every "4 Saros cycles of approx 18.03 years and 4 Metonic cycles of approx 19.00 years" - i.e (4 x 19.00 x 365.25 days) - (4 x 18.03 x 365.25 days) = 1417.17 days - equaling four lunar years difference (which is the actual basis for reconciling the solar and lunar cycles). I suspect that these two distinct observations are therefore somehow related.

  • $\begingroup$ Since all Saros series are the same length of time, any pattern between them must repeat at regular intervals. $\endgroup$
    – user21
    Jul 26, 2018 at 16:11
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    $\begingroup$ Saros cycles are the same length of time. Saros series are not. What governs the fact that there are 40 numbered series "active" at any given time? How frequently are new Saros series "born".? Is there a pattern that governs the new ones? I actually went back to Saros 9 for further comparison. These are not just random Saros numbers. $\endgroup$
    – user22542
    Jul 26, 2018 at 16:42
  • $\begingroup$ Another way to say it is this: - consider - 40 new Saros series are born during the lifespan of the first Saros series. Each new Saros series appears to begin with a wide range of spacing between them, but that is about one new series beginning (on average) every 31.5 years. Each Saros cycle within a series is always 18 yrs and 11.3 days. $\endgroup$
    – user22542
    Jul 26, 2018 at 21:02
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    $\begingroup$ Rephrased question ------ So then, what BEGINNING criteria lead to the birth of a new SERIES, and are the BEGINNING criteria somehow linked to the ENDING criteria of another series (40 earlier) in the numbering system? $\endgroup$
    – user22542
    Jul 26, 2018 at 21:12
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    $\begingroup$ Not 40-year pattern - repeat - Not 40-year pattern ---I am asking about 40 greater-numbering difference pattern. The End of one SERIES possibly leads to the Beginning of another SERIES (which has a 40 greater number value for the NEW SERIES - roughly 1260 years later). ARE THEY RELATED----hypothetically---by the cosmic conditions that ended the first and gave rise to the second? $\endgroup$
    – user22542
    Jul 29, 2018 at 19:52

1 Answer 1


It's been 3 years and I wondered if you found further answers on this. It's sad the answers here don't relate to your question. I too wanted to find this out.

On the non overlapping, the 12 cycles are deducted from saros 120, so 83-12 = 71 eclipses or 70 cycles of 1260 years. thus these same 12 eclipses will not be deducted within saros 80 since it's "accounted" for in saros 120. For Saros 80, Saros 40 last till -71; so the first 2 eclipses in saros 80 is overlapped and not counted so it'll be 74-2 = 72 eclipses.

I wondered if there's a way to exclude/include "overlapped periods" between eclipses to make it constant at 70 cycles of 1260 years for each saros.

This is because whenever a saros series is only 71 eclipses/70 cycles of 1260 years, no overlapping occur, so it is sort of "standalone"/constant.

It still puzzles me why the saros numbering with interval of 40 able to lead to this linkage of saroses via 1418 days. there must be an obscure cycle in the interval of rising of saros series.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – called2voyage
    Sep 7, 2021 at 19:20

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