From: Rainer Arlt, International Meteor Organisation
Date: Nov. 22, 1997


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            I M O   S h o w e r   C i r c u l a r
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                         LEONIDS 1997

The 1997 Leonid peak was expected to occur over North American west
coast longitudes and Hawaii on November 17. The strong moonlight
caused difficulties in determining the limiting magnitudes, resulting
in large scatters of the ZHRs. This Circular does not claim to
give first average ZHRs -- it rather tries to find the actual peak
time. ZHRs should be treated as relative values, since more elaborate
calibration of the moonlight observations may be necessary when more
data have been received.

The peak time fell between 10h30 UT and 13h UT. The exact time is
hard to derive, since several observers reported sharp activity
peaks at different times within this period. Average rates suggest
11h UT, which is the same peak solar longitude (sol=3D235.17) as
in 1996. Based on the data available, it is not possible to recognize
double peaks or filamentary structures. The scatter and temporal
variations are assumed to be caused by the poor conditions we had to
face this year.

We gratefully thank all the observers who made their observations
available by sending them to the Visual Commission or publishing
them on one of the meteor mailing lists.

Abdo Sana'a (Jordan)            Johannink Carl (the Netherlands)
Al-Alwanew Mohammad (Jordan)    Langbroek Marco (the Netherlands)
Al-Mualla Ramez (Jordan)        Lukic Vladimir (Yugoslavia, obs. USA)
Al-Niamat Ahmad (Jordan)        Lunsford Bob (USA)
Assmus Joseph (USA)             Miskotte Koen (the Netherlands)
Brown Peter (Canada, obs. USA)  Odeh Mohammad (Jordan)
Collier Matthew (USA)           Odwan Ibrahim (Jordan)
Dalee Hani (Jordan)             Sanchez Javier (Spain)
Davis Mark (USA)                Stomeo Enrico (Italy)
Gliba George (USA)              Taibi Richard (USA)
Gorelli Roberto (Italy)         Togni Rocky (USA)
Gramer Lewis (USA)              Trigo Josep M. (Spain)
Hally Wayne (USA)               Yrjola Ilkka (Finland)
Haver Roberto (Italy)           van Weerden Anne (the Netherlands)
Hernandez David (Spain)         Zay George (USA)


1997 Nov 17
---------------------
Time  Sollong ZHR  +-
(UT)  (J2000)
---------------------
0130  234.77   33   4
0400  234.87   35   7
0600  234.96   41  27
0815  235.05   66  31
0950  235.12   77  30
1050  235.16  132  43
1150  235.20   71  30
1250  235.24   95  33

2300  235.67   45  15
---------------------

The ZHRs are calculated with a population index of r=3D2.0 and a
zenithal exponent of 1.0. A large relative scatter of rates
appears at the interface between observations from the Canary
islands and North American east coast observers, indicating a
zenithal exponent different from 1.0. Errors are the standard
deviations of the average.