Archived posting to the Leica Users Group, 1999/12/18
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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.
>
>------------------------------------------------------------------
____________________________________________
alex@zetetic.co.uk
http://www.users.globalnet.co.uk/~abrattell/
___________________________________________