Tue, 14 Dec 1999 14:10:49 -0500

I've been getting assaulted by this one for the past few days.  Even more
than the usual "when is the real millennium" questions (answer is 2001, BTW
:-)  )

The coincidence of Full Moon with the solstice is about every 19 years...the
Metonic Cycle.  The coincidence of a Full Moon at lunar perigee (and the
for the year at that) is about every 13.5 months.  The coincidence of
lunar perigee, Full Moon, and winter solstice is a bit more rare...on the
of once a Century.

However, claims of a brighter Moon are quite overblown.  The difference
Full Moon at closest lunar perigee and earth perihelion versus Full Moon at
lunar apogee
and earth aphelion amounts to about 1/3 of a magnitude...-12.6 vs. -12.9.
Moon's so bright to begin with that most folks couldn't detect the
unless they had a good pocket photometer.

The claim about headlights being superfluous is a bit of a stretch.  The Sun
still nearly 200,000 times brighter than the Full Moon, so it'll still be
dark no matter how much snow cover there is!



| Geoff Chester  Public  Affairs Office |
|             US Naval Observatory |
| (202) 762-1438              3450 Massachusetts Avenue, NW |
| (202) 762-1489 (FAX)                Washington, DC  20392 |
| "Each passing hour brings the Solar System 43,000 miles   |
| closer to the globular cluster M13 in Hercules; yet there |
| are still some misfits who insist there's no such thing   |
| as progress!"     --    Ransom K. Fern                    |

> -----Original Message-----
> From: []
> Sent: Tuesday, December 14, 1999 13:19
> To:
> This is slightly off-topic, but it will affect our ability to observe.
> Plus, its interesting astronomical stuff.
> Merry Christmas,
> Troy
> PS -- I don't have any reference material or links for this.  
> It is word of
> mouth to me.
> <snip>
>  Brightest Full Moon in 133 years on the Winter Solstice
>  For the first time in the life of anyone around today, we'll 
> see a full
>  moon occur on the Winter solstice, Dec. 22nd, commonly 
> called the first day
>  of Winter. 
>  Since a full moon on the Winter solstice occurs in conjunction with a
>  lunar perigee (point in the moon's orbit that is closest to 
> Earth),the moon
>  will appear about 14% larger than it does  at apogee (the 
> point in its
>  elliptical orbit that is farthest from the Earth). Since the 
> Earth is also
>  several million miles closer to the sun at this time of the 
> year than in
>  summer, sunlight striking the moon is about 7% stronger 
> making it brighter.
>  Also, this will be the closest perigee of the Moon of the 
> year since the
>  moon's orbit is constantly deforming. If the weather is 
> clear and there is
>  snow cover where you live, it is believed that even car 
> headlights will be
>  superfluous. On December 21st, 1866 the Lakota Sioux took 
> advantage of this
>  combination of occurrences and staged a devastating 
> retaliatory ambush on
>  soldiers in Wyoming Territory. In layman's terms: It will be 
> a super bright
>  full moon, much more than the usual AND it hasn't happened 
> this way for 133
>  years! Our ancestors 133 years ago saw this. Our descendants 
> 100 or so
>  years from now will see this again.
>  Pretty cool, eh?
> <snip>
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