lunar calendar cycle & draconic year

[Helios]

I have, on this list, favored a lunar cycle of 51649 days which gives a mean month of 29 & 928 / 1749 days. Now it seems that the draconic year figures into the scheme of things.

= 107 yerms
= 149 draconic years
= 1749 months
= 51649 days

Here are empirical examples of eclipses over 51649 day cycles that I found while looking at NASA Phases-of-the-Moon web site,

http://eclipse.gsfc.nasa.gov/phase/phasecat.html

------------------JULIAN CALENDAR--------------------------
JD 1735610.5 ( CE 39 November 5 UT Thursday ) Partial Eclipse
JD 1787259.5 ( CE 181 April 2 UT Sunday ) Partial Eclipse
JD 1838908.5 ( CE 322 August 29 UT Wednesday ) Partial Eclipse
JD 1890557.5 ( CE 464 January 25 UT Saturday ) Annular Eclipse
JD 1942206.5 ( CE 605 June 22 UT Tuesday ) Annular Eclipse
JD 1993855.5 ( CE 746 November 18 UT Friday ) Total Eclipse
JD 2045504.5 ( CE 888 April 15 UT Monday ) Annular Eclipse
JD 2097153.5 ( CE 1029 September 11 UT Thursday ) Total Eclipse
JD 2148802.5 ( CE 1171 February 7 UT Sunday ) Annular Eclipse
JD 2200451.5 ( CE 1312 July 5 UT Wednesday ) Total Eclipse
JD 2252100.5 ( CE 1453 December 1 UT Saturday ) Annular Eclipse
---------------------------------------------------------------------

[Tom Peters-6]

Op 14-sep-2009, om 8:27 heeft Helios het volgende geschreven:

> I have, on this list, favored a lunar cycle of 51649 days which  
> gives a mean
> month of 29 & 928 / 1749 days. Now it seems that the draconic year  
> figures
> into the scheme of things.
>
> = 107 yerms
> = 149 draconic years
> = 1749 months
> = 51649 days

Hm, interesting: this does not seem to be a known eclipse cycle, see:
http://www.phys.uu.nl/~vgent/eclipse/eclipsecycles.htm

It is pretty good though: 1749 synodic months is 51648.9999... days
1898 draconitic months is 51648.7951... days
But it is 1874.427... anomalistic months, so the size of the Moon  
will vary a lot from one eclipse to the next.

--
Tom Peters

[Helios]

Dear Tom et al.

There's one more straggler that seems to complete this eclipse cycle. The thing looks like it lasts 17 centuries. I am considering these times as approximate ( averaged ) new-moon-at-midnight occurrences for the prime meridian.The fact that they are eclipses is entirely fortuitous but very noteworthy.

------------------JULIAN CALENDAR--------------------------
JD 1735610.5 ( CE 39 November 5 UT Thursday ) Partial Eclipse ( - 21 m )
JD 1787259.5 ( CE 181 April 2 UT Sunday ) Partial Eclipse ( - 294 m )
JD 1838908.5 ( CE 322 August 29 UT Wednesday ) Partial Eclipse ( + 235 m )
JD 1890557.5 ( CE 464 January 25 UT Saturday ) Annular Eclipse ( - 413 m )
JD 1942206.5 ( CE 605 June 22 UT Tuesday ) Annular Eclipse ( + 398 m )
JD 1993855.5 ( CE 746 November 18 UT Friday ) Total Eclipse ( - 354 m )
JD 2045504.5 ( CE 888 April 15 UT Monday ) Annular Eclipse ( + 216 m )
JD 2097153.5 ( CE 1029 September 11 UT Thursday ) Total Eclipse ( + 7 m )
JD 2148802.5 ( CE 1171 February 7 UT Sunday ) Annular Eclipse ( - 267 m )
JD 2200451.5 ( CE 1312 July 5 UT Wednesday ) Total Eclipse ( + 500 m )
JD 2252100.5 ( CE 1453 December 1 UT Saturday ) Annular Eclipse ( - 833 m )

------------------GREGORIAN CALENDAR--------------------------
JD 2303749.5 ( CE 1592 May 9 UT Tuesday) ( + 670 m ) Not an Eclipse
JD 2355398.5 ( CE 1736 October 5 UT Friday) Partial Eclipse ( - 426 m )