[time-nuts] Calculating time of lunar eclipse

[Magnus Danielson]

Hi,

On 2019-01-21 08:07, Mark Sims wrote:
> While on the subject of the accuracy/reliability of various algorithms and web pages showing various astronomical data, we had a full moon / total lunar eclipse in the northern hemisphere.  And not just any full moon, but a Super Blood Werewolf Zombie Apocalypse full moon (or some such drivel spouted by all the TV stations).
>
> Anyway, I wanted to know when the eclipse was at it's maximum.  Most web sites gave a time here as 23:12,  some differed by several minutes.  None gave the time to the second.  That just won't do for a moon worshiping time-nut, will it?  So, I tricked up a version of Lady Heather to do a screen dump when the difference of the  sun and moon azimuth and elevation were at a (180 degree) minimum.  Looks like it happened at 23:12:04

Well, the best time as we see it is actually about a second after it 
actually occurred, due to the time it takes for the light of the moon to 
reach us. So the time for the actual event and the time for observation 
becomes notisable different.

Cheers,
Magnus

> Heather's sun position code (based on Grena's algorithm 5) is VERY accurate (and quite simple).  The moon position code is pretty good... a better version would require several thousand lines of code evaluating a zillion polynomials with hundreds of terms.
>
> Anyway,, attached is a copy of the screen dump.  Note the difference in the sun/moon az/el values and also the calculated moon phase.
>
> Does anybody know of a reliable source of the true time of the lunar eclipse down to the second (or better)?
>
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