(meteorobs) Florida Geminids 2007Dec12/13

[Norman W. McLeod III]

Rates and magnitudes first, for 2007 Dec 12/13 night all clear by MCLNO, 
lat 26.5N, long 81.5W :

1110 - 1226 EST   0410 - 0526 UT  Field 120 +25  Teff 
1.27  F1.0   LM6.8   17 GEM   3 SPO  20 TOTAL

1226 - 0126 EST   0526 - 0626 UT  Field 135 +25  Teff 
1.00  F1.0   LM6.7   13 GEM   6 SPO  19 TOTAL

0126 - 0226 EST   0626 - 0726 UT  Field 150 +25  Teff 
1.00  F1.0   LM6.7   11 GEM   3 HYD   2 MON  2 SPO  18 TOTAL

0226 - 0326 EST   0726 - 0826 UT  Field 165 +25  Teff 
1.00  F1.0   LM6.7   25 GEM   1 STA   3 SPO  29 TOTAL

0326 - 0426 EST   0826 - 0926 UT  Field 180 +25  Teff 
1.00  F1.0   LM6.7   21 GEM   1 HYD   1 MON  6 SPO  29 TOTAL

0426 - 0534 EST   0926 - 1034 UT  Field 195 +25  Teff 
1.13  F1.0   LM6.7   30 GEM   2 HYD   3 SPO  35 TOTAL


Geminid magnitudes by the same periods as above :

0410 - 0526 UT   LM6.8   0 (5)   1 (3)    2 (6)   3 (0)   4 (3)   TOTAL 17

0526 - 0626 UT   LM6.7   -2 (1)   -1 (0)   0 (2)   1 (1)    2 (4)   3 
(4)   4 (1)   TOTAL 13

0626 - 0726 UT   LM6.7   -4 (1)    0 (1)   1 (3)    2 (3)   3 (0)   4 
(3)   TOTAL 11

0726 - 0826 UT   LM6.7   -2 (2)   -1 (0)   0 (2)   1 (3)    2 (8)   3 
(1)   4 (5)   5(4)   TOTAL 25

0826 - 0926 UT   LM6.7   -4 (1)   -1 (0)   0 (4)   1 (2)    2 (5)   3 
(4)   4 (4)   5(1)   TOTAL 21

0926 - 1034 UT   LM6.7   -1 (2)   0 (1)   1 (3)    2 (9)   3 (4)   4 
(5)   5 (4)   6 (2)    TOTAL 30


Sporadics :

0410 - 0526 UT   LM6.8   3 (2)   4 (1)   TOTAL  3

0526 - 1034 UT   LM6.7   -1 (1)   0 (2)   1 (1)    2 (4)   3 (2)   4 
(6)   5 (4)     TOTAL 20


Others for period 0526 - 1034 UT   LM6.7 :

MON   1 (1)    2 (1)   3 (0)   4 (1)    TOTAL 3

HYD    -2 (1)   -1 (1)   0 (0)   1 (0)    2 (2)   3 (1)   4 (1)    TOTAL 6

STA    1 (1)  TOTAL 1

---------------------

A comfortably cool night with temps in mid-60's.  We lost the next 2 nights 
almost completely to clouds and rain.  Still trying to verify my impression 
since 2001 that the Geminids have begun their decline.  Tentatively this 
night shows that unfortunate trend.  I'll have to wait 2 more years to get 
more data.  Looking up past years that preceded a leap year I have the 
following local hourly Geminid rates with times matched exactly :

Eight hours 9-10 through 4-5.
1975  LM7.0  x,x,x,x,x,52,35,34
1979  LM7.0  25,31,44,39,x,x,x,x
1983  LM7.5  x,x,28,x,56,56,32,54  3rd hr was LM6.0
1991  LM7.0  x,x,36,34,31,25,x,x   3rd and 4th hrs were LM7.2
2007  LM6.7  x,x,14,13,11,25,21,28  3rd hr was LM6.8

2007  LM7.2  x,x,16,15,13,29,24,33  rates corrected to LM7.2 using my 
personal factor 0.86
               (I lose about 14% of the sporadic meteors when sky LM drops 
from 7.0 to 6.5, so this is an approximate correction.)

2007  LM7.2  x,x,18,17,20,19,12,18  Felix Martinez rates same hours.

The higher 2007 rates in the last 3 hours indicates that timing of the 
activity curve has shifted westward compared with 20 years ago.  The same 
thing has happened with the Quadrantids.  Even taking that into 
consideration, the overall rates are much less than in earlier years.   I 
looked into the slightly inferior 2007 sky as well in the final line -- 
even here the corrected rates are lower than the past observed rates.  No 
surprise at all with the Geminids only due to be around for a couple more 
centuries.  It was great to be actively observing their best years 1979 to 
1996.

Rates for Felix Martinez observing with me are shown in the last line.  He 
started off in the same manner as long ago : around 1.3X my  perception, 
but instead of gaining further on me and surging the final hour like he 
used to, he pooped out from the fatigue of long days of driving to get 
here.  I didn't fade at all, and this was my first 6-hour observing session 
since 1996.

Norman







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Norman W. McLeod III
Staff Advisor
American Meteor Society

Fort Myers, Florida
nmcleod at peganet.com