At 17:57 03/01/97 +0100, Gianni Ferrari wrote:
>Warren Thorn wrote :
>
>> With the help of the basic programs from Sky & Telescope, I have
>> worked on the question of how many full moons will fall on Christmas
>> in the next 100 years. (3-2015,2072,2091) Someone at church said
>> we would not have a full moon on Christmas for over 100 years---I
>> knew that was not likely. There are several programs for date, time,
>> right ascension, and declination. The URL for Sky & Telescope is:
>>
>> <http://www.skypub.com/software/software.shtml>
>
>In "Astronomical Tables of Sun, Moon and Planets" by J. Meeus and using
>the Jeffrey Sax's programs distributed by Willmann-Bell and based on
>Astronomical Algorithms by J. Meeus
>I've found that Full Moon will fall in Christmas day 5 times in next
>century .
>Exactly in 2015 (11h 13m UT), 2034 (8h 56m), 2053 (9h, 24m) ,2072(7h 18m),
>2091(22h 02m)
>: the intervals respect the Saros Cycle
>The Full Moon will fall in the Holy Night ( as in 1996 at 20h 42m UT) only
>4 times : 2007 ( 1h 17m) ,2026 (1h 29m), 2045 (0h 45m), 2093 (3h 53m) .
>
>Perhaps at church someone said that we would not have a full moon on
>Christmas for over 100 years (also in Italy I've heared this news by
>radio) because for the persons not keened on astronomy the Holy Night
>begins about at 18h (12/24) and ends about 6h (12/25) and in this period
>there is no Full Moon ( at Greenwich obviously) .
>
> Please accept my apologies since this note not concerns Sundials
>
> Ciao Gianni
>
I do not wish to sound impolite but isn't there a reasonably well known
thoery that the lunar cycle repeats every 19 years. This is known as the
Metonic Cycle and was first devised about 430 BC by Meton of Athens.
100 divided by 19 is about five and a quarter so, if there is ever a Full
Moon on Christmas Day, approximately three centuries in four will have five
Full Moons on Christmas Day and approximately one century in four will have six.
OK I realise that the cycle is not exactly nineteen years and dare say that
one could argue about exactly what is meant by a Full Moon occurring on
Christmas Day but once in a thousand years seems a little far fetched.
As I said earlier I hope that this obsevation does not appear impolite - or
even wrong in which case I will "have egg all over my face!!!"
I hope that this is of asstistance.
Regards
-----------------------------------------Andrew
Pettit-----------------------------------------
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