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Old January 31st 18, 09:29 PM posted to uk.sci.astronomy
Martin Brown[_3_]
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Posts: 189
Default Of moon and tides

On 31/01/2018 18:03, N_Cook wrote:
On 31/01/2018 16:17, Martin Brown wrote:
On 31/01/2018 14:16, N_Cook wrote:
A quirk of celestial mechanics.
As the last blood-red , blue-moon, super-moon was 31 March 1866 we'll
have to wait 55458 days for the next coincidence of the tides in the
channel , presumably.
I wonder what conjuction of tidal harmonics gives a 55,458 day repeat.


It is double the named "Short Callipic Cycle" 2I+S = 75.9y 27729.22d

27729.22 x 2 = 55458.44 but according to the catalogue is unnamed.

I = Inex ~29y and S = Saros ~18y

They are the fundamental periodicities that allow you to catalogue
eclipse cycles. It will be interesting to see if the strong tides this
year drive any climatic effects from deep ocean mixing.

http://www.staff.science.uu.nl/~gent...ipsecycles.htm

Inex gives you an eclipse about the same longitude but opposite latitude
and 3x Saros gives you about the same eclipse conditions in about the
same place on the Earth. Or for an overviews and better explanation

https://eclipse.gsfc.nasa.gov/SEsaro...riodicity.html


Ta for that, I'll let the local NOC academic oceanographers know, to
avoid too much head-scratching.
Â*Next stop Milankovitch cycles


Checking there was also a nice juicy total lunar eclipse in 1942 Mar 3
which is midway between the one you quoted and now (ie every 2I+S).

https://en.wikipedia.org/wiki/March_1942_lunar_eclipse

Any interesting tides observed back then?

The one later in the year promises to have better UK visibility but we
still won't see totality well - moon will rise in eclipse for the UK:

https://www.space.com/33786-lunar-eclipse-guide.html

Some of these empirical eclipse rules have been known since Babylonian
times! Predicting solar eclipses was a blood sport in the early days of
colonising China when Ferdinand Verbiest nearly got killed before
inflicting that fate on the indigenous lazy court "astronomers".

https://en.wikipedia.org/wiki/Ferdin...onomy_contests

Enjoy! Sometimes truth is stranger than fiction.

--
Regards,
Martin Brown