Archived posting to the Leica Users Group, 1999/12/18

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Subject: [Leica] Re: full moon
From: Alex Brattell <>
Date: Sat, 18 Dec 1999 13:19:47 +0000

Don't mean to nitpick - just thought I'd forward this!

>                 BRIGHTEST FULL MOON IN 133 YEARS? NO!
>Suddenly a lot of people are asking this question: Will the full Moon of
>December 22, 1999, be the brightest full Moon in 133 years? They're asking,
>apparently, because of an article from the Old Farmer's Almanac that is
>being widely circulated by e-mail.
>According to Roger W. Sinnott, associate editor of SKY & TELESCOPE
>magazine, the answer is unequivocal: No!
>It is true that there is a most unusual coincidence of events this year. As
>S&T contributing editor Fred Schaaf points out in the December 1999 issue
>of SKY & TELESCOPE, "The Moon reaches its very closest point all year on
>the morning of December 22nd. That's only a few hours after the December
>solstice and a few hours before full Moon. Ocean tides will be
>exceptionally high and low that day."
>But to have these three events -- lunar perigee (the Moon's closest
>approach to Earth during its monthly orbit), solstice, and full Moon --
>occur on nearly the same day is not especially rare. The situation was
>rather similar in December 1991 and December 1980, as the following dates
>and Universal Times show (to convert Universal Time to Eastern Standard
>Time, subtract 5 hours):
>       Event        Dec. 1999      Dec. 1991     Dec. 1980
>       ---------------------------------------------------
>       Full Moon     22, 18h        21, 10h       21, 18h
>       Perigee       22, 11h        22,  9h       19,  5h
>       Solstice      22,  8h        22,  9h       21, 17h
>What is really rare is that in 1999 the three events take place in such
>quick succession. On only two other occasions in modern history have the
>full Moon, lunar perigee, and December solstice coincided within a 24-hour
>interval, coming just 23 hours apart in 1991 (as indicated in the preceding
>table) and 20 hours apart back in 1866. The 10-hour spread on December 22,
>1999, is unmatched at any time in the last century and a half.
>So is it really true, as numerous faxes and e-mails to SKY & TELESCOPE have
>claimed, that the Moon will be brighter this December 22nd than at any time
>in the last 133 years? We have researched the actual perigee distances of
>the Moon throughout the years 1800-2100, and here are some perigees of
>"record closeness" that also occurred at the time of full Moon:
>                       Date         Distance (km)
>                   -------------------------------
>                   1866 Dec. 21        357,289
>                   1893 Dec. 23        356,396
>                   1912 Jan.  4        356,375
>                   1930 Jan. 15        356,397
>                   1999 Dec. 22        356,654
>                   2052 Dec.  6        356,421
>It turns out, then, that the Moon comes closer to Earth in the years 1893,
>1912, 1930, and 2052 than it does in either 1866 or 1999. The difference in
>brightness will be exceedingly slight. But if you want to get technical
>about it, the full Moon must have been a little brighter in 1893, 1912, and
>1930 than in either 1866 or 1999 (based on the calculated distances).
>The 1912 event is undoubtedly the real winner, because it happened on the
>very day the Earth was closest to the Sun that year. However, according to
>a calculation by Belgian astronomer Jean Meeus, the full Moon on January 4,
>1912, was only 0.24 magnitude (about 25 percent) brighter than an "average"
>full Moon.
>In any case, these are issues only for the astronomical record books. This
>month's full Moon won't look dramatically brighter than normal. Most people
>won't notice a thing, despite the e-mail chain letter that implies we'll
>see something amazing.
>Our data are from the U.S. Naval Observatory's ICE computer program, Jean
>Meeus's Astronomical Algorithms, page 332, and the August 1981 issue of SKY
>& TELESCOPE, page 110.