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(meteorobs) Fw: IMO Shower Circ. PER 1999
Forwarded from the International Meteor Organization.....Mark
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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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PERSEIDS 1999
The perfect coincidence with the total solar eclipse on August 11
let many amateurs be on holidays and at a place good for meteor
observing too. The new Moon served with dark nights, and particularly
south-eastern Europe was lucky with widely clear skies, and, as
usual, Near Eastern observers enjoyed good weather as well. This
allowed for a good coverage of the 'new' Perseid peak, expected for
near 23h UT, which has been noticed since 1988 and seems to be
declining in activity. The traditional Perseid maximum should fall
near 4h UT on August 13, but poor weather has limited the efforts
of many east-coast observers in the US. Other American observers
were fortunately more lucky.
We are very grateful to the following observers who sent in their
results quickly and allowed the computation of the below ZHR graph:
Nada Abanda (ABANA, Jordan), Rainer Arlt (ARLRA, Germany),
Emad Ashi (ASHEM, Jordan), Jure Atanackov (ATAJU, Slovenia),
Juan A. Aveledo (AVEJU, Cuba), Lars Bakmann (BAKLA, Denmark),
Martin Bily (BILMA, Czech R.), Louis S. Binder (BINLO, USA),
Polona Bizjak (BIZPO, Slovenia), Tina Bizjak (BIZTI, Slovenia),
Lukas Bolz (BOLLU, Germany), Michael Boschat (BOSMI, USA),
Asdai Diaz Rodriguez (DIAAS, Cuba), Khalid Eid (EIDKH, Jordan),
George W. Gliba (GLIGE, USA), Michal Haltuf (HALMI, Czech R.),
Takema Hashimoto (HASTA, Japan), He Jingyang (JINHE, China),
Javor Kac (KACJA, Slovenia), Vaclav Kalas (KALVA, Czech R.),
Kevin Kilkenny (KILKE, USA), Andre Knofel (KNOAN, Germany),
Jakub Koukal (KOUJA, Czech R.), Ales Kratochvil (KRAAL, Czech R.),
Ralf Kuschnik (KUSRA, Germany), Marco Langbroek (LANMA, Netherlands),
Adrian Lelyen (LELAD, Cuba), Robert Lunsford (LUNRO, USA),
Hartwig Luthen (LUTHA, Germany), Pierre Martin (MARPI, Canada),
Antonio Martinez (MARTI, Venezuela), Tony Markham (MARTO, UK),
Alastair McBeath (MCBAL, UK), Mark Mikutis (MIKMR, USA),
Koen Miskotte (MISKO, Netherlands), Sirko Molau (MOLSI, Germany),
Francisco Munoz (MUNFR, Cuba), Jens O. Olesen (OLEJE, Denmark),
Kazuhiro Osada (OSAKA, Japan), Radame Perez (PERRA, Cuba),
Suyin Perret (PERSU, Venezuela), Maciej Reszelski (RESMA, Poland),
Mileny Roche L. (ROCMI, Cuba), Marion Rudolph (RUDMA, Germany),
Qi Rui (RUIQI, China), Ja'far Sabah (SABJA, Jordan),
Maria Shihadeh (SHIMR, Jordan), Milos Weber (WEBMI, Czech R.),
Oliver Wusk (WUSOL, Germany), Kim S. Youmans (YOUKI, USA),
Ilkka Yrjola (YRJIL, Finland), Jure Zakrajsek (ZAKJU, Slovenia),
George Zay (ZAYGE, USA), Ju Zhao (ZHAJU, USA),
Xiaojin Zhu (ZHUXI, China), Vladimir Znojil (ZNOVL, Czech R.).
For this first overview, only observations near the maximum were
considered. Many more covering the activity period of the Perseids
have been received already.
A rough profile of the population index was computed showing the
typical climb-down from r-values near 2.5 to 2.0, a few hours
after the maximum reaching 1.8. The values were used to compute
the ZHR profile as given below. The population indices given in
the last column are interpolated values from the rough profile
which has only 0.25 degree resolution at its best.
--------------------------------------------------
Solarlong Date Periods nPER ZHR +- r
(eq.2000) 1999, UT
--------------------------------------------------
138.251 Aug 11 0820 10 159 29.2 2.3 2.43
138.669 Aug 11 1850 15 195 34.0 2.4 2.57
138.786 Aug 11 2140 42 510 29.3 1.3 2.55
138.899 Aug 12 0030 38 510 32.8 1.4 2.47
139.149 Aug 12 0650 19 453 46.7 2.2 2.16
139.224 Aug 12 0840 9 293 45.0 2.6 2.14
139.570 Aug 12 1720 7 417 82.4 4.3 2.08
139.719 Aug 12 2100 9 107 60.7 5.8 2.11
139.752 Aug 12 2150 19 228 69.3 4.6 2.11
--------------------------------------------------
139.778 Aug 12 2231 4 67 74.0 9.0 2.11 * resolution ~12 min.
139.783 Aug 12 2239 7 64 97.3 12.1 2.11
139.787 Aug 12 2245 11 110 100.5 9.5 2.11
139.798 Aug 12 2301 9 127 100.7 8.9 2.13
139.805 Aug 12 2312 9 125 96.9 8.6 2.14
139.814 Aug 12 2325 12 124 92.0 8.2 2.16
139.819 Aug 12 2333 15 150 87.0 7.1 2.17
139.830 Aug 12 2349 13 132 87.6 7.6 2.19
139.834 Aug 12 2355 14 134 87.5 7.5 2.20
139.840 Aug 13 0004 8 103 81.8 8.0 2.21
139.853 Aug 13 0024 5 79 93.5 10.5 2.23
139.861 Aug 13 0036 8 95 88.9 9.1 2.23
139.866 Aug 13 0043 9 98 77.6 7.8 2.23
139.878 Aug 13 0101 11 132 86.0 7.5 2.22
139.882 Aug 13 0107 10 121 86.7 7.9 2.21
139.892 Aug 13 0122 7 79 85.8 9.6 2.20
139.896 Aug 13 0128 4 53 87.0 11.8 2.20 * end high resolution
--------------------------------------------------
139.901 Aug 13 0140 10 198 76.8 5.4 2.19
140.000 Aug 13 0400 1 45 91.7 13.5 2.09 * note: only 1 obs.
140.127 Aug 13 0720 27 556 60.3 2.6 1.85
140.153 Aug 13 0750 34 831 61.4 2.1 1.84
140.287 Aug 13 1120 8 288 64.4 3.8 1.81
140.717 Aug 13 2200 23 488 48.3 2.2 2.12
140.764 Aug 13 2310 31 889 53.0 1.8 2.13
140.858 Aug 14 0130 9 414 60.9 3.0 2.15
141.236 Aug 14 1100 2 90 53.6 5.6 2.15
141.729 Aug 14 2320 4 44 24.1 3.6 2.15
--------------------------------------------------
The general acitivity level of the Perseids was not exciting in
1999. A clear maximum with ZHR~100 appears near 139.79 (eq. J2000.0;
August 12, 2250 UT). Please note that the averages do cover several
observers, though often only a single observer group, and systematic
effects may be present in this first analysis -- peak time and ZHR
can be easily different by 1 hour and 20 meteors/h respectively. We
dare to conclude that the 'new' peak of the Perseids is to be
vanishing next year, in two years at the latest.
The high value of ZHR~90 at 140.0 (August 13, 0405 UT) is supposed
to mark the traditional Perseid maximum, but is based on a single
observation due to bad weather over large areas of the eastern
United States.
The peak of ZHR~80 at 139.57 is based on a number of observing
periods from two high-perception observers; more observations from
Asian longitudes will be necessary to find a comprehensive average.
A detailed analysis will follow in one of the future issues of
WGN, the Journal of the IMO.
-----------------------------------------------------
Rainer Arlt, 1999 Aug 21.
Visual Commission - International Meteor Organization
visual@imodot net - http://www.imodot net
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