GNU bug report logs - #61460
30.0.50; Calendar shows eclipse for quarter moon

Previous Next

Full log

Message #62 received at 61460 <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Ulrich Mueller <ulm <at> gentoo.org>
Cc: 61460 <at> debbugs.gnu.org
Subject: Re: bug#61460: 30.0.50; Calendar shows eclipse for quarter moon
Date: Tue, 14 Feb 2023 06:30:33 +0100

Ulrich Mueller <ulm <at> gentoo.org> writes:

> https://en.wikipedia.org/wiki/Argument_of_latitude
> | It is the sum of the more commonly used true anomaly and argument
> | of periapsis.

I did not find good discussions of the eclipse limits in the English
Wikipedia version; I found good explanations in German however:

  https://de.wikipedia.org/wiki/Finsternis-Limit#Finsternis-Limite_bei_Sonnenfinsternissen

  https://de.wikipedia.org/wiki/Finsterniszyklus

AFAIU you can indeed use similar values for lunar vs. solar eclipses.
But in the case of the moon, we are then including penumbral lunar
eclipses - in the total version see

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

which are probably not really interesting (moon gets only a bit darker).

The limits for an eclipse to happen are not really constant, but taking
this into account is probably out of scope of the currently available
code in lunar.el.

Michael.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.