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(meteorobs) Re: SW Florida 2000Nov17/18 Leonids very good



We had a very good show of Leonids for a couple of hours in SW Florida.
Joan had her best night ever, seeing 113 undifferentiated meteors in 3
hours.  It was quite comfortable with temp around 65F but mosquitoes were a
bit annoying.  Using skin-so-soft reduced that problem.

I noticed the same rate pattern here as already reported from elsewhere.
Rates were increasing after 645 UT but seemed to top out early.  My best
period was 701 - 716 UT with 27 Leonids in LM6.2 sky.  The tape recorder was
all set to go if rates passed 3/minute, but that never came close.  After
716 it fell off rather sharply.  By 831 there was little going on --
conditions were also dropping but observing was still possible.  We quit at
916 UT when fog became worse, cutting LM to 4.5 and hardly any Leonids
around.  I was writing blind on folded paper columns, 4 columns per page, to
minimize dead time.

There were no simultaneous Leonids seen here.  The best I achieved was two
of them less than a second apart, and three within 5 seconds.  I consider
the commonly used phrase  "several were seen at once"  to really mean
"several were seen in quick succession."   Leonids being the swiftest of
all, it would be very difficult to have two of them in view at the same
instant.  I had none simultaneous even in 1966 with a rate of 30/minute as
dawn and fog were moving in.

This was the night I needed to try for a new meteor total record, but it
didn't come close.  My record came on 1985 Dec 13/14 for Geminids with 621
total meteors seen.  In 1966 the Leonid storm peak came after sunrise in
Tallahassee, Florida so I was stopped at 591 meteors.  There's always next year.

Pierre Martin and I have almost identical relative rate levels in 5-minute
intervals. His perception is more than twice mine, hence his absolute rates
are higher by a factor of 2+.  I found our correlations very interesting.
In the past with ordinary showers, observing separately from others and then
looking for common periods of briefly higher rates completely failed.

An approximate ZHR calculation to find what I personally would have seen
with the Leonid radiant overhead is this.  The radiant elevation correction
factor would be about 2, from the radiant being about 30 degrees high at the
time I saw 27 Leonids in 15 minutes.  Going from LM6.2 to 6.5 for me would
gain about 10% in rates.  So the ZHR = 104 observed * 2 / 0.9 = 231, a
reasonable value.

Full hourly rates first :

2000 Nov 17/18, lat 26.5N, long 81.5W

126 - 226 EST   626 - 726 UT   LM 6.2    63 LEO    2 NTA   1 STA    2 SPOR
68 TOT

226 - 236 EST   726 - 826 UT   LM 5.8    64 LEO    1 AND   3 SPOR    68 TOT

An incomplete hour with fog increasing :

326 - 416 EST    826 - 916 UT   LM5.5  Teff 0.866  20 LEO   1 SPOR   21 TOT

Five-minute intervals follow, Leonids only :

UT, Teff, Leonids

LM6.2
620 - 626   0.100    3
626 - 632   0.100    2
632 - 638   0.100    2
638 - 644   0.100    3
644 - 651   0.117    6
651 - 656   0.083    7
656 - 701   0.083    7
701 - 706   0.083    7
706 - 711   0.083    10
711 - 716   0.083    8
716 - 721   0.083    4
721 - 726   0.083    5

LM6.2 ends, LM5.8 begins

726 - 731   0.083    5
731 - 736   0.083    8
736 - 741   0.083    6
741 - 746   0.083    5
746 - 751   0.083    5
751 - 756   0.083    5
756 - 801   0.083    6
801 - 806   0.083    7
806 - 811   0.083    3
811 - 816   0.083    6
816 - 821   0.083    1
821 - 826   0.083    7

LM5.8 ends, LM5.5 begins

826 - 831   0.083    6
831 - 836   0.083    2
836 - 841   0.083    1
841 - 846   0.083    3
846 - 916   0.500    8

Leonid magnitudes, LM6.2 only, range  -2m to +5m:
3,6,7,5,16,13,9,7 ; total 66, average  2.05m.

Leonid magnitudes, LM5.8 only, range  -5m to +5m:
1,0,2,0,3,6,13,14,7,12,6 ; total 64, average  1.97m.

Norman



 
Norman W. McLeod III
Staff Advisor
American Meteor Society

Fort Myers, Florida
nmcleod@peganet.com

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