[time-nuts] Calculating time of lunar eclipse
Mark Sims
holrum at hotmail.com
Mon Jan 21 07:07:31 UTC 2019
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
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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