-------------------------------------
I M O S h o w e r C i r c u l a r
-------------------------------------
LEONID Activity 2000
Observers saw no unusual activity during the nights of
November 15/16 and 16/17, though certains variations in the
activity level require further scrutiny.
Zenithal hourly rates (ZHRs) seem to have risen from about
10 +/- 5 around Nov 16, 0h UT, to about 45 +/- 5 by 4h UT.
After that, the picture becomes less clear. Observers at the
Canary Islands report high rates at the beginning of their
observations, resulting in a peak with ZHR around 110 +/- 20
at 6h00m +/- 5m UT. Activity drops again down to about
65 +/- 20 afterwards, but American observers report average
activity around 100 +/- 10 between 6h45m and 8h30m UT, with
a possible peak around 8h10m +/- 10m of 150 +/- 20. Afterwards,
activity drops again significantly to 45 +/- 10 by 9h00m UT.
Due caution is needed in interpreting these activity
variation, for the following reasons:
1) Only a few observations contributed to each
peak. Unexperienced or very perceptive observers can
"inflate" ZHRs. On the other hand, the peaks cannot be
explained away by averaging effects alone, as they are
also noticeable in the individual observations of the
observers involved.
2) The bright Last Quarter Moon is a disturbing factor in
the observations which is not easy to account for
exactly. Several observers, both in Europe and North
America, report to have seen their best activity during
the beginning of their observation. One may speculate the
continuous hindrance from the bright light of the Moon
made observers less perceptive for fainter meteors after
a while, resulting in a "decreasing peak branch" at the
beginning of their observations.
If the above-mentioned variations in activity are real,
however, the Nov 16, 6h45m-8h30m UT enhancement in activity
with a possible peak around 8h10m UT may be associated with the
Earth passing the outer regions of the 1932 (2 revolutions
old) dust trail of the parent comet, 55P/Tempel-Tuttle, for
which a possible activity enhancement was predicted at 7h53m
UT by (among others) Asher and McNaught.
The following observers have contributed data immediately
after the event, from which the ZHR profile given below
has been derived:
Birger Andresen, Joseph Assmus, Neil Bone, Andreas Buchmann,
Marc de Lignie, Petros Georgopoulos, Robin Gray, Rosely
Gregio, Valentin Grigore, Wayne Hally, Zoltan Hevesi, Janne
Pyykkoe, Robert Lunsford, Alastair McBeath, Gilberto Klar
Renner, Josep Trigo, Vishnu Vardhan, Cis Verbeeck, Jean-Marc
Wislez, Ju Zhao, Jin Zhu, Xiaojin Zhu.
Date Time (UT) Sol. long. Intervals Leonids ZHR +-
(2000.0)
---------------------------------------------------------
Nov 15 22h05m 243.848 2 11 13 4
Nov 16 03h33m 234.067 1 7 8 3
Nov 16 21h16m 234.820 6 44 20 3
Nov 17 3h23m 235.076 5 37 40 7
Nov 17 4h47m 235.136 9 74 47 5
Nov 17 6h00m 235.187 3 30 108 20
Nov 17 6h16m 235.198 3 16 66 17
Nov 17 6h30m 235.208 3 11 63 19
Nov 17 7h22m 235.244 11 91 98 10
Nov 17 9h19m 235.322 5 31 45 8
---------------------------------------------------------
ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.
---
Marc Gyssens, 2000 November 17, 16h UT.
wgn@imo.net
---
LEONID Activity 2000
--- 2nd update ---
Update on Nov 16/17
First results on Asian/European observations on Nov 17/18
--------------------
During the night of Nov 16/17, nothing unusual was seen,
except for two peaks on Nov 17, around 6h UT and 8h UT,
respectively. Additional information indicates that both
peaks are real.
During the night of Nov 17/18, a broad maximum is noticeable
with Zenithal Hourly Rates (ZHRs) above 200 between roughly
Nov 18, 1h30m UT and Nov 18, 5h UT, culminating around the
time of the predicted Nov 18, 3h44m UT peak with ZHRs around
300. At this time, we have insufficient data to conclude
anything about the predicted Nov 18, 7h51m UT peak.
The Nov 17, 6h00m UT peak of 110 +/- 20 is essentially based
on 2 (non-independent) observations from Tenerife (Canary
Islands). Since our previous release, however, David
Martinez-Delgado and Pablo Rodriguez-Gil, also on Tenerife,
but on a site where cirrus clouds prevented regular
observations, report that they, too, noticed an enhancement
of the activity around 6h00m UT, with approximately 1 meteor
per minute for 10 minutes.
The Nov 17, 6h45m-8h30m UT activity enhancement (ZHR = 105
+/- 5) with possible peak around Nov 17, 8h10m +/- 10m UT
(ZHR = 150 +/- 20) is in good agreement with a note from
Pavel Koten (Ondrejov Observatory) who detected two peaks
with their backscatter meteor radar, at Nov 17, 8h02m and
8h15m UT, respectively. Tentatively, this period of
increased activity, in particular the peak(s), may be
associated with the Earth passing the outer regions of the
1932 (2 revolutions old) dust trail of the parent comet,
55P/Tempel-Tuttle, for which a possible activity enhancement
was predicted at Nov 17, 7h53m UT by (among others) Asher
and McNaught.
With regard to the Nov 17/18 data, the most striking feature
is the large scatter among individual ZHR values,
doubtlessly due to the disturbing influence of the bright
Last Quarter Moon, which cannot easily be accounted for
exactly. As a consequence, all observations must be
interpreted with great care.
Nevertheless, the averages exhibit a clear pattern. Rates
start rising around Nov 17, 22h UT, and reach values above
200 from about Nov 18, 1h30m UT onward. ZHRs continue to
rise until they almost reach the value of 300 around 3h45m
+/- 15m UT. Afterwards, the rates drop again. Whether the
increase in the last line of the table below is genuine,
remains uncertain at this point. Almost all observations
which contributed to this last value were done under very
good sky conditions (apart from the Moon, of course), which
in itself may already suffice to explain this slight anomaly.
It must be emphasized that the Nov 18, 3h45m UT peak in this
broad maximum is not very pronounced. Tentatively, this
maximum may be associated with the 1733 (8 revolutions old)
dust trail of the parent comet, 55P/Tempel-Tuttle, for which
a possible activity enhancement was predicted around Nov 18,
3h44m UT by Asher and McNaught. Whether the end of the
period covered by the table below shows the beginning of a
second maximum, possibly due to the 1866 (4 revolutions old)
dust trail of 55P/Tempel-Tuttle, for which Asher and
McNaught predicted a possible activity enhancement around Nov 18,
7h51m UT, remains to be seen.
The following observers have contributed data immediately
after the event, from which the ZHR profile given below
has been derived:
Birger Andresen, Rainer Arlt, Adrian Arquiola, Joseph
Assmus, Jure Atanackov, Neha Bhandari, Lukasz Bielun, Lukas
Bolz, Neil Bone, Andreas Buchmann, Marc de Lignie, Frank
Enzlein, Magdalena Gawla, Petros Georgopoulos, Roberto
Gorelli, Robin Gray, Rosely Gregio, Valentin Grigore, Wayne
Hally, Zoltan Hevesi, Tamas Hubay, Javor Kac, Primoz Kajdic,
Akos Kereszturi, Vinit Kulkarni, Zsolt Lantos, Harry
J. Lehto, Robert Leyland, Mike Linnolt, Robert Lunsford,
Alastair McBeath, Norman W. McLeod III, Sirko Molau,
Kiyohide Nakamura, Piotr Nawalkowski, Michael Nezel,
Arkadiusz Olech, Arvid Parnajpye, Natasa Petelin, Szaniszlo
Prohaszka, Nilesh V. Puntambekar, Tushar Purohit, Janne
Pyykkoe, Guo-ming Qin, Gilberto Klar Renner, Kulkarni
Rhishikesh, Victor R. Ruiz, Mikiya Sato, Tomoko Sato, Konrad
Szaruga, Kazumi Terakubo, Mihaela Triglav, Josep Trigo,
Arnold Tukkers, Varada Vaidya, Vishnu Vardhan, George
Varros, Cis Verbeeck, Jean-Marc Wislez, Anna Witas, Oliver
Wunsk, Ju Zhao, Jin Zhu, Xiaojin Zhu.
Date Time (UT) Sol. long. Intervals Leonids ZHR +-
(2000.0)
---------------------------------------------------------
Nov 15 22h05m 243.848 2 11 13 4
Nov 16 03h33m 234.067 1 7 8 3
Nov 16 21h16m 234.820 6 44 20 3
Nov 17 3h02m 235.062 9 50 33 4
Nov 17 4h53m 235.141 10 74 47 5
Nov 17 6h00m 235.187 3 30 108 20
Nov 17 6h16m 235.198 3 16 66 17
Nov 17 6h36m 235.212 4 22 57 12
Nov 17 7h59m 235.270 10 117 104 10
Nov 17 9h25m 235.330 10 64 44 5
Nov 17 13h15m 235.491 4 35 52 9
Nov 17 19h26m 235.752 7 58 58 8
Nov 17 22h51m 235.896 7 139 106 9
Nov 18 00h26m 235.962 5 30 107 20
Nov 18 01h15m 235.996 11 119 159 15
Nov 18 01h48m 236.019 10 193 213 15
Nov 18 02h16m 236.039 18 377 214 11
Nov 18 02h44m 236.058 16 283 209 12
Nov 18 03h19m 236.083 18 369 220 12
Nov 18 03h47m 236.102 33 493 292 13
Nov 18 04h15m 236.122 29 459 233 11
Nov 18 04h45m 236.143 14 116 225 21
Nov 18 05h27m 236.159 17 416 263 13
---------------------------------------------------------
ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.
---
Marc Gyssens, 2000 November 18, 11h UT.
wgn@imo.net
---
-------------------------------------
I M O S h o w e r C i r c u l a r
-------------------------------------
LEONID Activity 2000
--- 3rd update ---
Update on Nov 17/18
Also including American observations
--------------------
During the night of Nov 17/18, a broad maximum is noticeable
with Zenithal Hourly Rates (ZHRs) above 200 between roughly
Nov 18, 1h30m UT and Nov 18, 5h UT, culminating around the
time of the predicted Nov 18, 3h44m UT peak with ZHRs around
300. Around Nov 18, 5h UT, the descending branch of this peak
merges with the ascending branch of a second, equally broad
but somewhat higher maximum with ZHRs above 200 between
roughly Nov 18, 5h UT and Nov 18, 8h30m UT, culminating
around Nov 18, 7h15m with a peak ZHR around 450, about half
an hour earlier than the predicted Nov 17, 7h51m UT peak.
With regard to the Nov 17/18 data, the most striking feature
is the large scatter among individual ZHR values,
doubtlessly due to the disturbing influence of the bright
Last Quarter Moon, which cannot easily be accounted for
exactly. As a consequence, all observations must be
interpreted with great care.
Nevertheless, the averages exhibit a clear pattern. Rates
start rising around Nov 17, 22h UT, and reach values
above 200 from about Nov 18, 1h30m UT onward. ZHRs continue to
rise until they almost reach the value of 300 around Nov 18,
3h45m +/- 15m UT. Afterwards, the rates drop again. Towards
the end of the European observing window, rates no longer
fall and tend to increase again. This increase is matched
with the start of the American observing window which starts
with a steady increase in rates reaching the value of 300
already around Nov 18, 5h30m UT. Rates continue to rise to a
level of 450 around Nov 18, 7h15m +/- 15m UT. Afterwards,
rates drop sharply. Around Nov 18, 10hUT, rates become
comparable with the activity level before the first maximum.
Tentatively, the first maximum may be associated with the
1733 (8 revolutions old) dust trail of the parent comet,
55P/Tempel-Tuttle, for which a possible activity enhancement
was predicted around Nov 18, 3h44m UT by Asher and McNaught.
Similarly, the second maximum may be associated with the
1866 (4 revolutions old) dust trail of 55P/Tempel-Tuttle,
for which Asher and McNaught predicted a possible activity
enhancement around Nov 18, 7h51m UT, although the present
data suggests that this second maximum peaked about half an
hour earlier.
Radar data from Ondrejov Observatory, communicated by Pavel
Koten, and the Leibniz Institute for Atmospheric Physics,
communicated by Ulf von Zahn, confirm the general picture
exhibited by the visual observations. At this time, however,
we do not wish to make strong statements about the precise
positions of the respective peaks of the two maxima, as they
are not very sharp. Nevertheless, it must be mentioned that
several individual North-American observers at very
different locations explicitly reported that they had the
impression the second peak occurred earlier than predicted.
Finally, we wish to observe that many observers mentioned
that the two maxima were rich in bright meteors. Whether
this is a subjective impression or an objective fact can
only be decided from a careful analysis of the magnitude
distributions, which is beyond the scope of these first
releases.
The following observers have contributed data immediately
after the event, from which the ZHR profile given below
has been derived:
Birger Andresen, Rainer Arlt, Adrian Arquiola, Joseph
Assmus, Jure Atanackov, Felix Bettonvil, Neha Bhandari,
Lukasz Bielun, Lukas Bolz, Neil Bone, Michael Boschat,
Andreas Buchmann, Bill Burton, Christian Castillo, Susan
Delaney, Marc de Lignie, Michael Doyle, Frank Enzlein, Yuwei
Fan, Magdalena Gawla, Petros Georgopoulos, Roberto Gorelli,
Lew Gramer, Robin Gray, Rosely Gregio, Valentin Grigore,
Wayne Hally, Roberto Haver, Zoltan Hevesi, Tamas Hubay,
Emmanuel Jehin, Kevin Jones, Tomsilav Jurkic, Javor Kac,
Primoz Kajdic, Akos Kereszturi, Albert Kong, Wen Kou, John
Krempasky, Vinit Kulkarni, Zsolt Lantos, Ken Legal, Harry
J. Lehto, Robert Leyland, Mike Linnolt, Jerry Lodriguss,
Robert Lunsford, Pierre Martin, Jose A.R. Martins,
S. Maticic, Alastair McBeath, Norman W. McLeod III, Huan
Meng, H. Mikuz, Sirko Molau, Kiyohide Nakamura, Piotr
Nawalkowski, Michael Nezel, Dragana Okolic, Arkadiusz Olech,
Kazuhiro Osada, Alexei Pace, Arvid Parnajpye, Natasa
Petelin, Ulhas Pradhan, Szaniszlo Prohaszka, Mayuresh
Prabhune, Nilesh V. Puntambekar, Tushar Purohit, Janne
Pyykkoe, Guo-ming Qin, Francisco A. Rodriguez Ramirez,
Gaurav Rathod, Gilberto Klar Renner, Kulkarni Rhishikesh,
Manuel S. Ruiz, Victor R. Ruiz, Carlos Saraiva, Mikiya Sato,
Tomoko Sato, Miguel A. Serra, Brian Shulist, Yuying Song,
Bjoern Soerheim, Konrad Szaruga, Richard Taibi, Kazumi
Terakubo, Sanjay Thorat, Mihaela Triglav, Josep Trigo,
Arnold Tukkers, Varada Vaidya, Erwin van Ballegoij, Vishnu
Vardhan, George Varros, Cis Verbeeck, Jean-Marc Wislez, Anna
Witas, Jonderko Wojciech, Oliver Wunsk, Dan Xia, Karen
Young, Ju Zhao, Jin Zhong, Jin Zhu, Xiaojin Zhu.
Mark Davis was instrumental in forwarding observations sent
to the Meteorobs mailing list.
Date Time (UT) Sol. long. Intervals Leonids ZHR +-
(2000.0)
---------------------------------------------------------
Nov 15 22h05m 243.848 2 11 13 4
Nov 16 03h33m 234.067 1 7 8 3
Nov 16 21h16m 234.820 6 44 20 3
Nov 17 3h02m 235.062 9 50 33 4
Nov 17 4h53m 235.141 10 74 47 5
Nov 17 6h00m 235.187 3 30 108 20
Nov 17 6h16m 235.198 3 16 66 17
Nov 17 6h36m 235.212 4 22 57 12
Nov 17 7h59m 235.270 10 117 104 10
Nov 17 9h25m 235.330 10 64 44 5
Nov 17 15h00m 235.565 7 74 50 6
Nov 17 19h22m 235.750 14 237 69 5
Nov 17 23h01m 235.903 9 164 102 8
Nov 18 00h27m 235.963 7 62 101 13
Nov 18 01h14m 235.995 15 170 161 12
Nov 18 01h47m 236.018 13 264 219 14
Nov 18 02h17m 236.040 25 496 211 10
Nov 18 02h45m 236.059 24 518 232 10
Nov 18 03h17m 236.082 31 668 236 9
Nov 18 03h46m 236.101 45 809 296 10
Nov 18 04h14m 236.121 41 827 247 9
Nov 18 04h45m 236.143 21 274 218 13
Nov 18 05h13m 236.163 17 440 225 11
Nov 18 05h44m 236.184 11 404 336 17
Nov 18 06h22m 236.211 13 346 337 18
Nov 18 07h12m 236.246 10 547 457 20
Nov 18 07h45m 236.269 15 372 374 19
Nov 18 08h14m 236.289 14 555 272 12
Nov 18 08h40m 236.308 8 133 152 13
Nov 18 09h22m 236.337 9 222 80 5
Nov 18 11h08m 236.411 9 162 42 3
---------------------------------------------------------
ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.
---
Marc Gyssens, 2000 November 19, 2h UT.
wgn@imo.net
---