An updated profile of the Leonid meteor activity was computed. The data collected are still producing a noisy picture. An enhancement of activity is found on November 13, between 12h UT and 24h UT. This coincides with the predicted encounter time with the 1499 dust trail of Comet 55P/Tempel-Tuttle. The clearest feature of the profile is the activity maximum on November 19, between 0h UT and 22h UT. No sharp peak time is found. Predictions were given for the 1533 dust trail encoun- ter between 6h30 and 8h UT. The predictions mentioned are based on caluclations by Asher, Lyytinen, Nissinen, McNaught, and Vaubaillon. Lyytinen obtained additionally an encounter with the 1733 trail for November 19, 16h50 UT. The long duration of the observed November 19 peak maybe attributed to the superposition of the two encounters. Data are not sufficient though to derive more precise peak times. ------------------------------------------------------ Date (UT) Time Solarlong nINT nLEO ZHR ------------------------------------------------------ Nov 13.05 01:12 230.184 3 9 14 +- 4 Nov 13.50 12:00 230.637 4 13 27 +- 7 Nov 13.67 16:05 230.808 12 15 13 +- 3 Nov 13.73 17:31 230.868 17 59 21 +- 3 Nov 13.78 18:43 230.918 12 50 19 +- 3 Nov 14.01 00:14 231.150 7 9 22 +- 7 Nov 14.77 18:29 231.915 1 2 (41) +- 24 Nov 15.71 17:02 232.861 6 8 15 +- 5 Nov 15.80 19:12 232.952 7 20 16 +- 3 Nov 16.67 16:05 233.828 16 38 14 +- 2 Nov 17.37 08:53 234.534 8 16 13 +- 3 Nov 17.72 17:17 234.887 17 65 18 +- 2 Nov 18.44 10:34 235.613 13 42 15 +- 2 Nov 19.03 00:43 236.208 14 91 40 +- 4 Nov 19.11 02:38 236.289 13 111 41 +- 4 Nov 19.17 04:05 236.349 14 96 32 +- 3 Nov 19.26 06:14 236.440 6 16 39 +- 9 Nov 19.34 08:10 236.521 13 69 27 +- 3 Nov 19.42 10:05 236.601 12 117 35 +- 3 Nov 19.63 15:07 236.813 23 292 63 +- 4 Nov 19.91 21:50 237.096 19 51 43 +- 6 Nov 20.20 04:48 237.389 18 171 32 +- 2 Nov 20.92 22:05 239.126 8 21 14 +- 3 Nov 21.66 15:50 238.863 11 40 7 +- 1 Nov 22.18 04:19 239.388 7 17 10 +- 2 Nov 22.91 21:50 240.126 8 26 11 +- 2 Nov 23.15 03:36 240.369 7 28 6 +- 1 ------------------------------------------------------ A population index of r=2.3 was used to extrapolate to lm=+6.5. All solar longitudes refer to equinox J2000.0. nINT is the number of observing periods, nLEO the number of Leonid meteors. Many of the observations suffer from low limiting magnitudes, and the value of the limiting magnitude may be systematically over- or underestimated. We derived the median of the sporadic hourly rates of all the observing periods and obtain <HR> = 16 which is typical for November. Observers reporting at least 10 sporadics meteors are corrected according to the ratio of their average sporadic rate to 16. Rainer Arlt, 2003 November 25, 9h UT
New moon on 1 May provided favourable observing conditions for the Eta-Aquarids this year. By 8 May, 19 observers repor- ted 322 Eta Aquarids in 71.02 h net observing time. In gen- eral, rather low activity was recorded (ZHRs~30) with an extended 4-day plateau and no apparent maximum. ----------------------------------------------------------- Date UT sollong n_ind n_obs nETA ZHR +/- ----------------------------------------------------------- 03 May 0050 42.16 7 7 19 26.2 6.4 04 May 0330 43.24 6 11 38 26.4 4.4 05 May 0150 44.14 11 17 70 32.2 3.8 05 May 1810 44.80 2 3 16 12.3 3.0 06 May 0130 45.10 8 13 61 36.6 4.6 06 May 1810 45.77 3 3 26 20.4 3.9 07 May 0120 46.06 8 13 67 31.3 3.8 07 May 2000 46.81 1 2 9 21.8 6.9 08 May 0140 47.04 4 4 16 27.1 6.6 ----------------------------------------------------------- Solar longitudes refer to equinox J2000.0. n_ind is the number of individual observers, n_obs is the number of individual observing periods, nETA is the number of Eta-Aquarids observed. The radiant position was assumed at alpha=338deg, delta=-1deg, the population index used was r=2.4. The expectation value of the ZHR, ZHR = (1 + sum nLYR) / sum(Teff/C), was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limit- ing magnitude and cloud coverage. Error bars are derived as err=sqrt(1+sum nLYR). We are very grateful to the following observers for their efforts, impressions and quick reporting of data: Alexandre Amorim (Brazil) Jure Atanackov (Slovenia) Ana Bankovic (Serbia) Aleksandra Dimitrievska (Serbia) Petros Georgopulos (Greece) Daniel Gruen (Germany) Shy Halatzi (Israel) Carl Johannink (The Netherlands) Anna Levina (Israel) Irena Lisovski (Israel) Bert Matous (USA) Ian Musgrave (Australia) Bojana Obradovic (Serbia) Peta O`Donohue (Australia) Branislav Savic (Serbia) Juan Martin Semegone (Argentina) Ana Sovilj (Serbia) Oliver Wusk (Australia) Kim S. Youmans (USA) Information provided by A. Dubietis and R. Arlt 2003 May 09
The activity of the 2003 Lyrids was slightly below a normal annual level (ZHR=18), with the maximum as expected at sollong=32.3 degrees. However, the pre-maximum was not covered by observations. There is still a gap in observing times from 31.8 to 32.2 degrees of solar longitude (from 10h to 20h UT, April 22, which favors Asian, Near-East sites and Eastern Europe, to some extent). As by April 24, 13h UT, 15 observers have reported 191 Lyrids, 23 Saggitarids and 298 sporadics in 43.91 observing hours so far. Summary of 2003 Lyrid activity. ------------------------------------------------------------ Date UT Sollong n_ind n_obs nLYR ZHR err(+/-) ------------------------------------------------------------ 19 Apr 20:43 29.34 1 3 1 1.4 1.0 20 Apr 21:30 30.35 1 4 8 3.7 1.2 21 Apr 21:25 31.32 4 6 19 6.0 1.3 21 Apr 06:01 31.67 2 4 14 11.3 2.9 22 Apr 22:50 32.35 10 15 79 16.7 1.9 22 Apr 01:40 32.47 7 12 69 14.6 1.7 23 Apr 22:20 33.31 1 2 1 5.9 4.2 Solar longitudes refer to equinox J2000.0. n_ind is the number of individual observers, n_obs is the number of individual observing periods, nLYR is the number of Lyrids observed. The radiant position was assumed at alpha=271°, delta=+34°, the population index used was r=2.2. The expectation value of the ZHR, ZHR = (1 + sum nLYR) / sum(Teff/C), was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, cloud coverage and radiant height correction. Error bars are derived as err=ZHR/sqrt(1+sum nLYR). We are very grateful to the following observers for their efforts, impressions and quick reporting of data: Rainer Arlt (Germany) Audrius Dubietis (Lithuania) Darja Golikowa (Germany) Daniel Gruen (Germany) Shlomi Eini (Israel) Shy Halatzi (Israel) Anna Levina (Israel) Bert Matous (USA) Alastair McBeath (UK) Bruce McCurdy (Canada) Alex Mikishev (Israel) Arkadiusz Olech (Poland) Michel Vandeputte (Belgium) Kim S. Youmans (USA) Ilkka Yrjola (Finland) Information provided by Audrius Dubietis and Rainer Arlt. 2003 April 24, 14h UT
Two strong activity peaks of the Leonid meteor shower were predicted. The times fell between 03:48 to 04:04 UT for the first one, and between 10:23 to 10:47 UT for the second peak, both on November 19, 2002. A first activity analysis from the reports of 86 observers, who logged 19443 Leonids, is given below. The ZHR refers to a stellar limiting magnitude of +6.5, a radiant elevation of 90 deg, and counts of single observers. A population index of r=2 was applied, although the inspection of data suggests a large abundance of faint meteors, thus a larger r. The ZHRs would increase likewise. The peak time of the first maximum is 04:10 UT with ZHR=2350. The second peak is found near 10:50 UT or a few minutes ear- lier with ZHR=2660. Both peaks occurred later than the pre- dictions by about the same time lapse. The predictions of the Leonid stream model of Vaubaillon (WGN 30:5, 2002) are closest to reality according to this first analysis. -------------------------------------- Nov UT Sollong N LEO ZHR +- -------------------------------------- 16 2000 234.257 2 10 19 6 17 0300 234.551 6 15 6 2 17 2200 235.349 13 96 37 4 18 0400 235.601 12 78 26 3 18 2000 236.273 21 431 98 5 18 2300 236.399 22 195 100 7 19 0000 236.441 26 330 101 6 19 0110 236.490 27 271 188 11 19 0140 236.511 24 218 201 14 19 0210 236.532 21 266 249 15 19 0220 236.539 20 332 305 17 19 0240 236.553 36 342 300 16 19 0255 236.564 16 157 275 22 19 0306 236.571 22 205 375 26 19 0316 236.578 28 329 497 27 19 0327 236.586 27 484 583 27 19 0335 236.591 48 1047 756 23 19 0343 236.597 20 412 930 46 19 0345 236.599 32 719 1162 43 19 0353 236.604 35 768 1344 49 19 0358 236.608 47 1341 1542 42 19 0402 236.610 36 1248 1966 56 19 0408 236.615 31 1335 2353 64 19 0413 236.618 17 912 2332 77 19 0418 236.622 30 1253 1995 57 19 0426 236.627 35 933 1367 45 19 0436 236.634 38 681 989 38 19 0447 236.642 24 416 635 31 19 0500 236.651 31 395 675 34 19 0518 236.664 50 505 1014 45 19 0535 236.676 22 189 572 42 19 0555 236.690 15 97 144 15 19 0620 236.707 15 87 142 15 19 0800 236.777 14 166 272 21 19 0905 236.823 21 217 307 21 19 0930 236.840 27 99 152 15 19 0947 236.852 21 72 267 32 19 1000 236.861 21 128 293 26 19 1010 236.868 31 192 707 51 19 1018 236.874 19 396 907 46 19 1023 236.877 15 134 965 83 19 1030 236.882 27 288 1364 80 19 1040 236.889 26 350 2108 112 19 1050 236.896 28 587 2656 110 19 1100 236.903 19 297 1061 62 19 1112 236.912 17 130 490 43 19 1135 236.928 7 184 366 27 19 2200 237.366 6 99 123 12 20 0500 237.660 11 4 10 5 --------------------------------------------- Solar longitudes refer to equinox J2000.0, N is the number of observing periods involved in the average ZHR, LEO is the number of Leonid meteors. The error of the ZHR is simply ZHR/sqrt(LEO) here. No special zenith exponent was applied to account for non-geometrical effects in radiant elevation correction.
We are very grateful to the enthusiastic community of meteor observers who have sent in their results, mostly through the online express form. All observers are encouraged to send their FULL DATA including magnitudes and possibly shorter time-bins for the counts within the next week. (An error in the online form script has lead to erroneous out- put in geographical latitude and radiant elevation; the actual results presented here are not affected though.) V. Krumov, M. Gyssens, R. Arlt 2002 November 22
We present a first activity curve of the 2002 Perseids based on the reports of 140 observers from 30 countries as listed below. The averages include only observing periods with a total correction smaller than 8.0 and radiant elevations higher than 10 degrees. Since a number of new observers contributed to the profile, we made use of perception factors based on the total sporadic activity for all individuals. Details about the analysis will be found in an updated article in the October issue of WGN, the Journal of the IMO. This first curve was obtained with a constant populatsion index of r=2.0 and no corrections for the radiant elevation hR other than sin(hR).
The maximum of the 2002 Perseids falls near a solar longitude of 140.0 (eq. J2000.0), although the curve actually exhibits a plateau between 139.9 and 140.16 when ZHRs exceeded 80. Peak rates are about ZHR = 90 +-5. This result makes the 2002 Perseids a typical return, and the early peak seen in 1988-1999 does not appear or might at best be the (hardly significant) enhancement at sol=139.91.
---------------------------------------------- Date (UT) Sollong #Obs #PER ZHR +- ---------------------------------------------- Aug 2, 21:30 130.3762 5 10 8.4 2.5 Aug 4, 00:20 131.4479 16 40 7.2 1.1 Aug 5, 22:30 133.2870 12 106 14.2 1.4 Aug 7, 05:00 134.5055 8 63 11.8 1.5 Aug 8, 02:50 135.3795 21 166 16.0 1.2 Aug 8, 21:00 136.1065 10 135 27.0 2.3 Aug 9, 03:20 136.3613 37 476 18.6 0.9 Aug 10, 01:14 137.2351 22 299 25.9 1.5 Aug 10, 18:30 137.9254 23 345 29.2 1.6 Aug 11, 03:40 138.2901 57 808 33.5 1.2 Aug 11, 21:30 139.0022 33 406 38.1 1.9 Aug 12, 04:20 139.2746 37 931 62.2 2.0 Aug 12, 15:50 139.7384 30 946 75.4 2.5 Aug 12, 20:00 139.9056 43 941 89.1 2.9 Aug 12, 21:40 139.9723 53 968 82.6 2.7 Aug 12, 23:00 140.0231 47 973 87.6 2.8 Aug 13, 00:30 140.0821 37 866 83.4 2.8 Aug 13, 02:20 140.1614 36 983 87.4 2.8 Aug 13, 09:20 140.4398 22 482 65.0 3.0 Aug 13, 22:00 140.9438 50 966 49.8 1.6 Aug 14, 01:30 141.0818 56 820 44.0 1.5 Aug 14, 23:50 141.9778 36 465 25.4 1.2 Aug 15, 23:30 142.9231 17 136 15.3 1.3 Aug 16, 14:50 143.5420 5 28 12.3 2.3 Aug 16, 23:20 143.8795 11 55 13.2 1.8 ----------------------------------------------Solar longitudes refer to eq. J2000.0, #Obs is the number of observing periods included in the average, #PER is the number of shower meteors involved. The error margins are ZHR/sqrt(#PER).
We would like to thank the following contributors and the ones having sent their reports very recently who do not feature in the below list:
Ahmad Abdo (Jordan) Robert Lunsford (USA) Haitham Abdel Majid (Jordan) Hartwig Luthen (Germany) Sana'a Abdo (Jordan) Jin Ma (China) Puya Ahmadifard (Iran) Qiang Ma (China) Ardalan Alizadeh (Iran) Xiaoyun Ma (China) Ahmad Al-Niamat (Jordan) Alan Macrobert (USA) Karl Antier (France) Petra Maierova (Czech Republic) Jure Atanackov (Slovenia) Veikko Makela (Finland) Aleksandar Atevik (Macedonia) Radek Maly (Czech Republic) Javad Azizi (Iran) Grigoris Maravelias (Greece) Lars Bakmann (Denmark) Jose A. dos Reis Martins (Portugal) Adriyan Bozinovski (Macedonia) Pierre Martin (Canada) Jay Brausch (USA) Ashley Matous (USA) Emil Brezina (Czech Republic) Bert Matous (USA) Dustin Brown (USA) Alastair McBeath (UK) Stefan Cikota (Croatia) Huan Meng (China) Malcolm J. Currie (UK) Frederic Merlin (France) Hani Dalee (Jordan) Markko Meriniit (Estonia) Denis Denissenko (Russia) Rein Merendi (Estonia) Samer Derbi (Jordan) Ali Moosazadeh (Iran) Vincent Desmarais (Canada) Thom Morgan (USA) Peter Detterline (USA) Arash Nabizadeh (Iran) Miha Devetak (Slovenia) Goran Niksic (Croatia) Jaka Dobaj (Slovenia) Brian Nilsson (Denmark) Subo Dong (China) Markku Nissinen (Finland) Audrius Dubietis (Lithuania) Daniel van Os (Netherlands) Vedrana Dzaja (Croatia) Irena Pickova (Czech Republic) Shlomi Eini (Israel) Carles Pineda Ferre (Spain) Sven-Erik Enno (Estonia) Senka Pintaric (Croatia) Dunja Fabjan (Slovenia) Jurgen Rendtel (Germany) David Fernandez Barba (Spain) Mileny Roche Lamas (Cuba) Lukas Ferkl (Czech Republic) Miguel Serra Martin (Spain) Mildred Formosa (Malta) Mazyar Seyyednezhad (Iran) Martin Galea (Malta) Mohammad Reza Shafaroodee (Iran) Xing Gao (China) Sergey Shanov (Russia) George W. Gliba (USA) Quanzhi Shen (China) Darja Golikowa (Germany) Brian Shulist (Canada) Eva Grillova (Czech Republic) Julia Silina (Estonia) Daniel Grun (Germany) Masa Sinreih (Slovenia) Pavol Habuda (Slovakia) Hana Sipova (Czech Republic) Cathy Hall (Canada) Urmas Sisask (Estonia) Amir Hassanzadeh (Iran) Jiri Srba (Czech republic) Takema Hashimoto (Japan) Mark Stafford (USA) Harri Haukka (Finland) Enrico Stomeo (Italy) Veli-Pekka Hentunen (Finland) Wesley Stone (USA) Zoltan Hevesi (Hungary) Nikola Strah (Croatia) Ken Hodonsky (USA) Pavel Svozil (Czech Republic) Kamil Hornoch (Czech Republic) Richard Taibi (USA) Jurgen Janes (Estonia) Indrek Tallo (Estonia) Carl Johannink (Netherlands) Josep M. Trigo Rodriguez (Spain) Tomislav Jurkic (Croatia) Arnold Tukkers (Netherlands) Javor Kac (Slovenia) Shigeo Uchiyama (Japan) Mihkel Kama (Estonia) Michel Vandeputte (Belgium) Esam Kasasbeh (Jordan) Jan Verfl (Czech Republic) Gregor Kladnik (Slovenia) Johanna Vihalem (Estonia) Khalil Konsul (Jordan) Arash Voghoee (Iran) Petra Korlevic (Croatia) Quanzhi Ye (China) Marek Kozubal (Canada) Kim S. Youmans (USA) Dovile Krauleidiene (Lithuania) Robert Young (USA) Vladimir Krumov (Bulgaria) Yin Yue (China) Maris Kuperjanov (Estonia) Jure Zakrajsek (Slovenia) Nina Lampic (Slovenia) Joseph Zammit (Malta) Marco Langbroek (Netherlands) Jan Zavitski (Estonia) Anna S. Levina (Israel) Liu Zenglin (China) Chun Li (China) Bo Zhang (China) Xian Li (China) Kun Zhou (China) Yang Li (China) Jin Zhu (China) Michael Linnolt (USA) Ziyi Zhu (China) Andre Lipand (Estonia) Jurga Zieniute (Lithuania) Madis Lohmus (Estonia) Vladimir Znojil (Czech Republic)
Rainer Arlt &
Andreas Buchmann, 2002 August 19
Information provided by Rainer Arlt,
2002 January 25
Originally, the so-called 'preliminary reports' were meant as an immediate information about the observed activity level of major meteor showers based on a limited number of raw data sent to the IMO directly after the observations. This scheme worked well until the number of observers sending their (full) reports promptly increased so that we now reached a point where we receive an (almost) complete global data set within a few days after a major shower maximum. Of course, it is great to see that observers distribute their full data so quickly. This situation, however, implies that the people doing the input work for the IMO data bases will type the data only once. That is, we now have quite a large number of Geminid reports already in the VMDB (while still many Leonid and Geminid reports are coming in). As a further consequence, the present Geminid report is based on a large quantity of data obtained by 44 observers worldwide and it (almost) looks like a global analysis rather than a very preliminary report. This is also the reason for the delay...
Anyway, we very much appreciate the reports sent by the following 44 observers including 146.3h net observing time and a total of 5919 Geminids noted during the 2001 return of the shower:
Hershil Adesara (India) Koen Miskotte (Netherlands) Rainer Arlt (Germany) Sirko Molau (Germany) Felix Bettonvil (Netherlands) Sven Näther (Germany) Sushrut Bhanushali (India) Francisco Ocana Gonzalez (Spain) Lukas Bolz (Germany) Eran Ofek (Israel) Biswajit Bose (India) Daniel Van Os (Netherlands) Parag B. Deotare (India) Jacques Plee (France) Frank Enzlein (Germany) Nilesh Puntambekar (India) Christoph Gerber (Germany) Tushar Purohit (India) George W. Gliba (USA) Jürgen Rendtel (Germany) Shelagh Godwin (UK) Francisco Rodriguez Ramirez (Spain) Madhura Gokhale (India) Keren Sharon (Israel) Lew Gramer (USA) Brian Shulist (Canada) Takema Hashimoto (Japan) George Spalding (UK) Kamil Hornoch (Czech Republic) Ulrich Sperberg (Germany) Tomislav Jurkic (Croatia) Enrico Stomeo (Italy) Marco Langbroek (Netherlands) David Swann (USA) Robert Lunsford (USA) Richard Taibi (USA) Hartwig Luthen (Germany) Josep Trigo Rodriguez (Spain) Qiang Ma (China) Michel Vandeputte (Belgium) Pierre Martin (Canada) Heinrich Wiechell (Germany) Alastair Mcbeath (UK) Nikolai Wünsche (Germany)
Of course, we will include all further data becoming available later in the global analysis of the Geminids 2001 and publish a respective paper in WGN. The 2001 return was well observed and the data is particularly useful because the night was free of disturbing moonlight. The Geminids showed a broad maximum with a plateau with ZHRs of the order of 120. The last column gives the time (UT) for a number of solar longitudes.
sol_long ZHR +- Time (UT)
260.311 28 1.5 0720 Dec 12
260.395 31 1.7
260.505 33 2.0 1200
260.743 47 2.9
260.889 56 3.5
261.050 64 4.3 0050 Dec 13
261.145 69 4.3
261.217 73 4.9
261.439 78 4.6 1000
261.688 89 4.8
261.877 107 4.5
261.921 111 3.7 2120
261.972 110 2.4
261.996 118 2.3 2310
262.014 120 2.1 2345
262.036 118 1.9 0005 Dec 14
262.052 117 1.9 0025
262.066 116 1.8 0045
262.076 116 1.7 0100
262.084 116 1.7 0110
262.096 116 1.7 0130
262.109 116 1.8 0150
262.126 117 1.9 0210
262.148 118 2.1 0245
262.170 120 2.3 0315
262.195 114 2.5 0350
262.219 108 2.8 0425
262.250 108 3.4 0505
262.295 112 4.0 0610
262.349 112 4.6 0725
262.361 113 4.8 0745
262.374 117 5.7 0805
262.436 96 6.4 0930
262.742 44 2.4 1645
sol_long Solar longitude (2000.0)
ZHR, +- Geminid ZHR and error; the r value was determined
from the magnitude data; zenith exponent gamma=1.0
Time (UT) time in 2001, rounded to the nearest 5 min time stamp
Information provided by Jürgen Rendtel,
2001 December 28
The following 25 observers were included in the below analysis:
Rastislav Bagin, Chu-lok Chan, Yeon-jong Choi, George W. Gliba, Lew Gramer, Pavol Habuda, Xiaolin Huang, Richard Huziak, Martin Krsek, Martin Lehky, Michael Linnolt, Robert Lunsford, Hartwig Luthen, Monika Martiniskova, Peter Martinisko, Norman McLeod, Huan Meng, Sirko Molau, Peter Mrazik, Andrzej Skoczewski, Roger Venable, Miroslav Vetrik, Barbara Wilson, Dan Xia, Zhou Xingming.
The selection is simply caused by the process of entering data into the Visual Meteor Database; presence or absence of reports is not a measure of quality. Please do not complain your report is missing here -- hundreds of reports are actually missing as yet!
For the first time, a profile of the population index was computed. It covers the Asian peak and shows a significant increase of r during the peak. The population index was near 2.0 before and after the Asian peak. It may have been even lower for other periods which have not been covered, given the large number of bright meteors reported.
-------------------------------------------- Sollong NINT ZHR error r Date/Time (J2000) -------------------------------------------- 233.6803 6 10.7 2.4 2.00 234.8489 16 16.9 1.7 2.00 235.6417 23 33.6 2.4 2.00 235.7577 18 56.0 4.2 2.00 235.7948 17 72.4 5.2 2.00 235.8300 14 92.0 6.6 2.00 235.8681 14 86.3 6.1 2.00 236.0146 10 141.2 10.1 2.00 236.0442 8 198.7 16.8 2.00 236.0648 9 239.7 18.2 2.00 236.0791 4 312.4 23.4 2.00 236.0873 2 417.9 57.4 2.00 236.0936 6 474.7 34.6 2.00 236.1007 5 641.8 47.6 2.00 236.1090 8 664.1 49.0 2.00 236.1136 12 738.2 55.6 2.00 236.1177 13 691.3 48.9 2.00 236.1217 9 968.3 77.8 2.00 236.1249 10 1241.3 103.4 2.00 Nov 18 1021 236.1282 14 1067.0 77.8 2.00 Nov 18 1026 236.1308 11 1429.3 105.9 2.00 Nov 18 1030 236.1326 11 1032.8 87.0 2.00 Nov 18 1032 236.1348 12 1118.3 89.5 2.00 Nov 18 1035 236.1371 12 1309.6 95.0 2.00 Nov 18 1039 236.1389 9 1284.7 112.2 2.00 Nov 18 1041 236.1408 13 1160.3 86.0 2.00 Nov 18 1044 236.1435 15 1144.5 82.4 2.00 Nov 18 1048 236.1461 13 1006.6 76.8 2.00 Nov 18 1052 236.1495 13 829.9 64.6 2.00 236.1619 10 780.6 55.6 2.00 236.1725 16 735.6 56.9 2.00 236.1871 9 473.9 34.2 2.00 236.2458 8 319.7 22.9 2.00 236.3029 7 371.3 27.1 2.00 236.3256 6 397.6 29.5 2.00 236.3499 9 369.5 35.7 2.01 236.3797 36 507.6 27.1 2.02 236.3975 48 741.1 37.1 2.03 236.4073 45 903.8 46.4 2.03 236.4152 32 1239.2 62.8 2.04 236.4205 27 1321.2 71.1 2.04 236.4251 23 1503.8 76.0 2.05 236.4299 26 1280.1 69.2 2.05 236.4345 19 1753.5 88.5 2.08 Nov 18 1743 236.4386 17 1651.6 87.4 2.11 Nov 18 1749 236.4422 14 1848.2 103.2 2.15 Nov 18 1754 236.4457 14 2057.9 110.2 2.17 Nov 18 1759 236.4484 10 2242.5 130.6 2.17 Nov 18 1803 236.4515 18 1861.9 94.2 2.17 Nov 18 1807 236.4541 11 2112.8 125.4 2.17 Nov 18 1811 236.4561 9 2406.9 121.6 2.17 Nov 18 1814 236.4582 7 2196.5 150.5 2.16 Nov 18 1817 236.4600 10 2630.0 140.8 2.15 Nov 18 1820 236.4621 11 2192.9 121.6 2.15 Nov 18 1823 236.4644 12 1906.7 102.4 2.14 Nov 18 1826 236.4668 13 2370.8 120.2 2.15 Nov 18 1829 236.4690 9 2400.5 137.5 2.17 Nov 18 1832 236.4712 11 1958.0 109.6 2.20 Nov 18 1836 236.4739 13 2160.8 112.8 2.21 Nov 18 1839 236.4765 12 1656.7 93.3 2.18 Nov 18 1843 236.4798 16 1416.5 70.8 2.15 Nov 18 1848 236.4846 13 1482.9 77.9 2.10 Nov 18 1855 236.4882 14 1448.3 73.6 2.07 Nov 18 1900 236.4932 21 1051.6 52.6 2.03 236.4978 19 1222.4 63.0 2.01 236.5034 22 1108.2 55.8 1.99 236.5123 22 1087.2 55.6 1.96 236.5207 29 848.3 42.8 1.92 236.5317 31 759.0 38.7 1.90 236.5465 32 635.8 32.7 1.92 236.6595 40 208.6 10.7 1.96 --------------------------------------------
NINT is the number observing periods involved. We used the population index given in the last column, the zenithal exponent is 1.0. Averaging periods do not overlap; each period is used only once. Errors are the +-ZHR/sqrt(n) margins of the Leonid number n.
Information provided by Rainer Arlt,
2001 November 26
The strongest peak observed is around 18h20min UT which was suitably situated for the observers in East Asia and Australia. The rates during this peak reached more then 2800 meteors per hour. This is well below the theoretically predicted peak levels which were around 5000 according to Lyytinen/Nissinen/van Flaudern or 8000 in Asher/McNaught's model.
As far as the first peak, observed from America, is concerned rates were between 1000 and 1500 meteors per hour. However there is still not enough data reported from it especially about the time after 11 UT.
The first activity profile is derived from the observations of 38 observers. It is aimed to give a general view of the observed shower and no conclusions can be made on this stage. The following detail analysis will tell us more about the shower and the dust trail models.
Data of the following observers is included in the preliminary profile. The countries in brackets show the place where observations were carried out, not necessarily his home land :
Albert Kong (USA), Andreas Buchman (Germany), Andrzej Skoczewski (Poland), Antonio Martinez (Venezuela), Brian Shulist (Canada), Camila Bacher (USA), Carles Pineda Ferre (Spain), Detlef Koschny(Australia), Francisco A. Rodriguez Ramirez (Spain), Gaurav Rathod (India), Ina Rendtel (Germany), James Bedient (USA), Jaydeep Belapure (India), Joe Zemder (Australia), Josep M. Trigo-Rodriguez (Spain), Joseph Zammit (Malta), Kamil Hornoch (Pland), Ken Hodonsky (USA), Kim Youmans (USA), Marion Rudolph (Germany),Mark Davis (USA), Martin Galea De Giovanni (Malta), Mayuresh Girish Prabhune (India), Michael Doyle (USA), Miguel A. Serra (Spain), Mike Linnolt (USA), Rafael Haag (Brazil), Rainer Arlt (Korea), Robert Lunsford (USA), Shigeo Uchiyama Japan), Sirko Molau (Korea), Tom Roelandts (China), Tomislav Jurkic (Croatia), Umberto Mulè Stagno (Tunis), Valentin Velkov (Bulgaria), Werner Hamelinck (China), Xiaorong Wang (China), Zhou Xingming (China)
_____________________________________ Date Time Sollong Nint Nobs ZHR +/- -------------------------------------- 18 0100 235.732 23 8 52 4 18 0300 235.816 22 9 80 3 18 0500 235.900 21 8 95 5 18 0630 235.963 11 5 160 10 18 0730 236.005 15 7 200 10 18 0815 236.036 13 5 150 10 18 0845 236.057 15 5 270 15 18 0915 236.078 18 6 430 20 18 0945 236.099 12 6 570 20 18 1015 236.121 17 6 790 25 18 1045 236.142 20 5 1000 25 18 1130 236.173 8 2 400 40 18 1300 236.236 12 2 370 25 18 1430 236.299 9 1 320 20 18 1530 236.341 16 3 490 30 18 1630 236.383 16 3 780 40 18 1700 236.404 16 4 1100 50 18 1730 236.425 18 4 1550 50 18 1800 236.446 20 5 2320 60 18 1820 236.460 28 7 2850 60 18 1840 236.474 32 7 2430 50 18 1900 236.488 21 6 1580 50 18 1920 236.509 18 5 1160 40 18 1940 236.516 17 5 1020 40 18 2000 236.530 17 7 800 30 18 2030 236.551 13 5 470 20 18 2120 236.587 16 5 150 10 18 2220 236.629 7 4 130 10 ______________________________________
Calculations are made for population index r=2.0. Nint is the number of intervals observing intervals in a certain period. Nobs is the number of different observers in it.
Many thanks to all the observers that have contributed their data. Also to the favorable weather conditions whish are not so typical for this part of the year.
Information provided by Vladimir Krumov,
2001 November 19
In the following report observations of the following observers are used: Kim Youmans (USA, Albert Kong (USA), Valentin Velkov(Bulgaria), Joseph Zammit (Malta), Martin Galea De Giovanni (Malta), Andreas Buchman (Germany), Josep M. Trigo-Rodriguez (Spain), Camila Bacher (USA), Brian Shulist (Canada), Ina Rendtel (Germany), Marion Rudolph (Germany), Rafael Haag (Brazil), Umberto Mul\350 Stagno (Tunis), Michael Doyle (USA), Ken Hodonsky (USA).
What appears from these observations is that the peak is a little bit later that the predicted time (09h55m UT - Predicted by David Asher and Rob McNaught and 10h28m - Predicted by Esko Lyytinen, Markku Nissinen and Tom van Flandern). However this preliminary data can not be too reliable due to the small number of observers included. So any comments on the activity rates are quite hard to be made at this stage.
I wish you Clear Skies and lots of luck during the rest of this fantastic event!
Date Time (UT) SolLong NObs nINT nLeo ZHR +- ____________________________________________ 18 NOV 0100 235.732 4 5 53 42 6 18 NOV 0230 235.795 5 9 266 68 4 18 NOV 0400 235.858 5 9 246 105 7 18 NOV 0500 235.900 6 11 184 134 10 18 NOV 0600 235.942 4 8 110 167 16 18 NOV 0700 235.984 3 7 63 173 22 18 NOV 0800 236.026 4 7 211 269 19 18 NOV 0830 236.047 4 9 231 168 11 18 NOV 0900 236.068 3 7 267 340 21 18 NOV 0940 236.096 5 10 606 523 21 18 NOV 1000 236.110 5 10 698 846 32 18 NOV 1020 236.124 4 10 731 946 35 18 NOV 1040 236.138 4 8 792 1342 48 18 NOV 1050 236.145 3 6 465 1313 61 nINT - Number of observing intervals NObs - Number of observers
Information provided by Vladimir Krumov,
2001 November 18
As you may have noticed, our primary domain imo.net was down for almost a month. After numerous mail messages, telephone calls and internal contacts we could finally trace the problem. As we suspected right from the beginning, it was a fault of our domain registrar Network Solutions Inc., not on our side.
We would like to apologize for any inconvenience that the down-time of our domain may have caused. We also like to thank again the American Meteor Society, which hosts a mirror site of our homepage and ensured that most of our services were still available in the last few weeks.
From now on you can access our homepage under the primary URL www.imo.net again. The ftp server ftp.imo.net is accessible, too, and all mail addresses @imo.net are working again.
information provided by:
Sirko Molau
(2001/08/22)
The 2001 Perseids occurred under rather poor circumstances. Observers either had to put up with the adverse effects of a Last Quarter Moon or start early, in which case they had to deal with low radiant elevations. This resulted in a lot of scatter among individual data, from which it is hard to derive a clear pattern, especially in this early stage of data collection.
What we can conclude from the table below is that Perseid activity reached a very broad top level with a ZHR around 85 between roughly August 12, 9h UTC and the early UTC hours of August 13. There may have been one or more peaks in this long interval, they were surely not very outspoken. The individual ZHRs on which this table is based suggest such peaks around August 12, 14h UTC and August 12, 20h UTC, with ZHR of 130 and 105, respectively. Unfortunately, both possible peaks are covered by a few observers only, most of which are very perceptive, which is why these suspected peaks might be mere artefacts.
We remind the reader that the peak associated with the latest return of parent comet Swift-Tuttle could not be positively identified in the 2000 Perseid data. A very straightforward - but equally tentative - explanation of the current profile might be that whatever activity remains of the "first peak" smoothly flows over into the activity associated with the regular Perseid peak, thus creating a very wide and flat plateau of activity. A more thorough investigation of these and other data will be necessary to shed more light on this, obviously.
If you have not done so yet, please send your observing data as quickly as possible to the Visual Commission at visual@imo.net.
--------------------------------------------------- Date Time(UTC)Sollong nObs nInd nPER ZHR ± --------------------------------------------------- Jul22 0000 119.25 7 3 14 5.8 1.5 Jul27 0000 124.03 4 1 8 3.7 1.2 Jul28 0000 124.98 20 7 49 5.7 0.8 Jul29 0000 125.94 5 2 13 3.7 1.0 Jul30 0000 126.90 7 2 21 5.4 1.2 Aug07 2100 135.39 3 1 8 13.2 4.3 Aug09 0000 136.47 5 1 12 12.6 3.5 Aug11 0000 138.38 6 6 81 37.4 4.1 Aug11 1430 138.96 6 3 79 66.9 7.4 Aug11 2115 139.23 16 13 233 46.1 3.0 Aug11 2230 139.28 15 12 273 45.1 2.7 Aug11 2330 139.32 14 10 192 61.3 4.4 Aug12 0050 139.38 15 10 223 69.4 4.6 Aug12 0150 139.42 13 9 297 55.8 3.2 Aug12 0415 139.51 10 5 175 54.5 4.1 Aug12 0900 139.70 13 6 357 82.8 4.4 Aug12 2000 140.14 16 7 226 91.2 6.1 Aug12 2120 140.20 24 9 320 71.4 4.0 Aug12 2230 140.24 23 12 398 64.9 3.2 Aug12 2330 140.28 19 9 342 93.8 5.1 Aug13 0030 140.32 19 10 368 83.0 4.3 Aug13 0150 140.38 13 6 423 103.2 5.0 Aug13 0800 140.62 3 3 245 52.7 3.4 Aug14 0000 141.26 4 2 77 40.9 4.6 ---------------------------------------------------
We thank all observers who contributed to the compilation of this first impression of the 2001 Perseids:
Karl Antier, Jure Atanackov, Michael Boschat, Dustin Brown, Andreas Buchman, Maria Butkovski, Jens Carsen, Audrius Dubietis, Vedrana Dzaja, Shlomi Eini, Petros Georgopoulos, George Gliba, Shelagh Godwin, Cathy Hall, Amir Hasanzadeh, Monika Hevesi, Zoltan Hevesi, Ken Hodonsky, Kamil Hornoch, Maja Hren, Carl Johannink, Javor Kac, Soheil Khoshbin Far, Katia Koleva, Dovile Kraulaidiene, Vedran Krecel, Anna Levina, Mike Linnolt, Hartwig Luthen, Christophe Marlot, Pierre Martin, Huan Meng, Ali Moosazadeh, Umberto Mule' Stagno, Jens Olesen, Alexei Pace, Senka Pintaric, Miguel A. Serra, Yuying Song, Wes Stone, Josep M. Trigo-Rodriguez, Kim S. Youmans, Jure Zakrajsek, Bo Zhou, Jurga Zieniute, and Mia Zuanic from Bulgaria, Canada, China, Croatia, Denmark, France, Germany, Greece, Hungary, Iran, Israel, Lithuania, Malta, the Netherlands, Slovenia, Spain, the United Kingdom, and the United States.
information provided by:
Marc Gyssens and
Vladimir Krumov
(2001/08/15)
Dust trails produced by Comet Schwassmann-Wachmann 3 near its perihelion passages may get close to the Earth and produce meteor activity. Computations of the evolution of such dust trails by H. Lüthen (Germany) showed an approach to the 1941 trail for May 30, 2001, 10h UT (solar longitude 69.04°). The encounter was not very close, and chances to see a meteor outburst were slim.
Several observers reported their results from visual and video monitoring in the nights of May 24 to May 30. Apart from very few possible shower members, no meteor activity from Schwassmann-Wachmann 3 was observed. Unfortunately, no report was received for the time after May 30, 12h UT.
The following observers sent in their observations directly to the Visual Commission or communicated their results via the mailing list 'meteorobs@jovian.com'. We are very grateful for their quick contributions.
ARLRA Rainer Arlt (Germany) BETFE Felix Bettonvil (the Netherlands, VIDEO) DECGO Goedele Decononck (Belgium) HOLDA David Holman (USA) JENPE Peter Jenniskens (USA) JOHCA Carl Johannink (the Netherlands) KOOMI Mike Koop (USA) LANMA Marco Langbroek (the Netherlands) LUNRO Robert Lunsford (USA) MOLSI Sirko Molau (Germany, VIDEO) RENJU Jurgen Rendtel (Germany) STORO Rosta Stork (Czech Republic, VIDEO) TRIJO Josep M. Trigo-Rodriguez (Spain) TUKAR Arnold Tukkers (the Netherlands) VERCI Cis Verbeeck (Belgium) --------------------------------------------------- May Observer Time (UT) N ZHR hR 2001 SW3 (app./true) --------------------------------------------------- 24 JOHCA 2154-2216 0 - 68/65 25 LANMA 2145-2245 1 1.5 68/64 25 TUKAR 2145-2245 0 - 68/64 25 JOHCA 2145-2305 1 1.2 67/63 25 TUKAR 2245-2345 0 - 63/59 25 LANMA 2246-0000 0 - 62/58 25 JOHCA 2305-0005 0 - 61/56 25 TUKAR 2345-0045 1 2.8 57/51 26 LANMA 0000-0112 0 - 54/48 26 JOHCA 0005-0105 0 - 54/48 26 TUKAR 0045-0115 0 - 52/45 29 STORO 2100-0130 1 (video obs.) 29 MOLSI 2103-0215 0 (video obs.) 29 BETFE 2200-0230 0 (video obs.) 29 DECGO 2250-0020 0 - 60/55 29 VERCI 2258-0020 0 - 60/55 29 RENJU 2300-0036 0 - 55/49 30 ARLRA 0017-0100 0 - 49/41 30 TRIJO 0203-0305 0 - 39/30 30 LUNRO 0830-0933 0 - 54/44 30 LUNRO 0933-1035 0 - 40/31 30 HOLDA casual 0 - 30 JENPE casual 0 - 30 KOOMI casual 0 - 30 LUNRO 1035-1138 0 - 30/18 ---------------------------------------------------
Solar longitudes refer to equinox J2000.0. The geocentric radiant position was assumed at alpha=212°, delta=+28°, the population index used was r=3.0. The radiant elevation is given as apparent and geocentric (true) values which differ strongly for a low-velocity shower such as the SW3-ids with an entry velocity of V_inf = 17 km/s.
It must thus be noted that shower association might be erroneous as the radiant does NOT APPEAR at alpha=212°, delta=+28° as given theoretically, due to zenithal attraction. The above values of hR (app./true) indicate differences of up to 10 degrees.
information provided by:
Rainer Arlt
(2001/05/31)
Very favourable lunar conditions made this shower a highlight target of 2001. Occasionally heightened activity is observed from the Lyrids, most notably in 1982. The 2001 maximum exhibited a slightly enhanced level of activity. Observations from 49 observers were collected by April 24, 0h UT. Such a large number of observations monitoring a shower of moderate activity is a fairly nice success of amateur meteor observing. The table of the activity graph is given below.
The maximum is broad; highest rates are found near a solar longitude of lambda = 32.0° with ZHR = 33±3. The first peak at lambda = 31.7° comprises a number of novice observers who may have underestimated their limiting magnitudes. Nevertheless, the up-and-down or -- more roughly speaking -- the general plateau shape of the activity profile appears to be a typical feature of the 2001 Lyrids. This was already found in recent Lyrid activity profile. This year, the plateau may extend over as much as 24 hours. ZHRs in 2000 were lower, 20 at best, in 1999 near 30 as this year, but again significantly lower in 1998 with values below 20.
------------------------------------------------------ 2001 Time Sollong nObs nIND nLYR ZHR Apr (UT) (J2000) ------------------------------------------------------ 17 0620 27.295 2 1 0 3 ±3 19 0600 29.237 1 1 0 7 ±7 20 0130 30.030 1 1 3 3 ±2 20 2200 30.864 6 2 13 5 ±1 21 0140 31.013 8 5 30 8 ±1 21 1800 31.678 8 7 85 37 ±4 21 2130 31.820 18 13 155 28 ±2 21 2320 31.894 13 13 67 18 ±2 22 0000 31.922 10 10 128 28 ±2 22 0100 31.962 14 12 117 19 ±2 22 0230 32.023 10 10 90 33 ±3 22 0900 32.287 8 5 54 27 ±4 22 2130 32.795 3 2 19 24 ±5 23 2200 33.791 2 2 7 8 ±3 ------------------------------------------------------
We are very grateful to the following observers for their efforts and quick reporting of data:
ANTDU Dusan Antic (Serbia) MENHU Huan Meng (China) ARLRA Rainer Arlt (Germany) MILAA Ana Milovanovic (Serbia) BASLU Luc Bastiens (Belgium) MISKO Koen Miskotte (Netherlands) BETFE Felix Bettonvil (Netherlands) MODAM Amruta Modani (India) BHANE Neha Bhandari (India) NISMA Markku Nissinen (Finland) BHASU Sushrut Bhanushali (India) PATSO Sonali Patil (India) DECGO Goedele Deconink (Belgium) PEEBJ Bjorn Peeters (Belgium) DEOPA Parag Deotare (India) PRAMA Mayuresh Prabhune (India) DUBAU Audrius Dubietis (Lithuania) PUNNI Nilesh Puntambekar (India) FANYU Yuwei Fan (China) RENJU Juergen Rendtel (Germany) GADSH Shirish Gadkar (India) SAVBR Branislav Savic (Serbia) GEOPE Petros Georgopoulos (Greece) SONWA Wanfang Song (China) GEYBE Benny Geys (Belgium) SUNHU Huiming Sun (China) GLIGE George Gliba (USA) TRIJO Josep Trigo-Rodriguez (Spain) GOLDA Darja Golikowa (Germany) TUKAR Arnold Tukkers (Netherlands) HASTA Takema Hashimoto (Japan) UCHSH Shigeo Uchiyama (Japan) JOHCA Carl Johannink (Netherlands) VELKR Kristina Veljkovic (Serbia) KULMA Manali Kulkarni (India) VERJN Jan Verbert (Belgium) KULRH Rhikesh Kulkarni (India) VUJKA Katarina Vujic (Serbia) KULVI Vineet Kulkarni (India) VUJRO Romana Vujasinovic (Serbia) LANMA Marco Langbroek (Netherlands) WANSH Shuo Wang (China) LINMI Mike Linnolt (USA) WISJE Jean-Marc Wislez (Belgium) LUNRO Robert Lunsford (USA) ZERZO Zorana Zeravcic (Serbia) MARAN Antonio Martinez (Venezuela) ZHUJI Jin Zhu (China) MCBAL Alastair McBeath (UK) ZUPLJ Ljubica Zupunski (Serbia)
Solar longitudes refer to equinox J2000.0. nObs is the number of individual observing periods, nIND is the number of individual observers providing them, nLYR is the number of Lyrids seen. The radiant position was assumed at alpha=271°, delta=+34°, the population index used was r=2.9. The expectation value of the ZHR,
ZHR = (1 + sum nLYR) / sum(Teff/C),
was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction. Times are rounded to the nearest 10 minutes.
information provided by:
Rainer Arlt and
Vladimir Krumov
(2001/04/24)
Favorable lunar conditions accompanied the maximum of the 2001 Quadrantid meteor shower. Peak activity was expected near 12h UT on January 3, corresponding to a solar longitude of lambda=283.16°.
Observers were satisfied by good Quadrantid rates in the UT afternoon and evening hours of January 3, 2001. Radio forward- scatter observations as reported by Hiroshi Ogawa, Japan, showed increased Quadratid activity until 20h UT on January 3, compared with the background activity of December 30-January 1. Geometrical effects of radiant direction changes will play a significant role though.
The highest ZHR value is found for 13h30m UT on January 3 or a solar longitude of lambda=283.24° (J2000.0). The ZHR of about 130 is a typical value for the Quadrantids, but the number of reports for the peak period is very small whence conclusions are tentative. The peak time may easily shift by one hour to either side once a more comprehensive dataset is available.
We are very grateful to the following 23 observers who sent their reports to the Visual Commission or to the various mailing lists in time for this first activity overview:
ANDBI Birger Andresen (Norway) MEIMA Marcel Meima (UK) BIVNI Nicolas Biver(USA) NICTE Ted A. Nichols II (USA) BURWI Wlliam Burton (USA) PUNNI Nilesh Puntambekar (India) DAVMA Mark Davis (USA) RENJU Jurgen Rendtel (Germany) GLIGE George W. Gliba (USA) SPAGE George Spalding(UK) GODSH Shelagh Godwin (UK) STOWE Wes Stone (USA) HALWA Wayne T. Hally (USA) TAIRI Richard Taibi (USA) HASTA Takema Hashimoto (Japan) TUKAR Arnold Tukkers (the Netherlands) HOSDA Dave Hostetter (USA) UCHSH Shigeo Uchiyama (Japan) JOHCA Carl Johannink (Germany) YOUKI Kim S. Youmans (USA) LINMI Mike Linnolt (USA) ZHUJI Jin Zhu (China) MCBAL Alastair McBeath (UK) --------------------------------------------------- Date Time (UT) Sollong nObs nIND nQUA ZHR --------------------------------------------------- Jan 02 2300 282.63 2 2 17 13 +- 9 Jan 03 0230 282.78 5 3 40 26 +- 4 Jan 03 0510 282.89 13 5 109 17 +- 3 Jan 03 0740 283.00 9 5 98 56 +- 6 Jan 03 0940 283.08 10 8 192 61 +- 4 Jan 03 1120 283.15 6 4 90 68 +- 7 Jan 03 1330 283.24 3 2 33 131 +-23 Jan 03 1500 283.31 4 3 53 118 +-16 Jan 03 1720 283.41 5 3 76 82 +- 9 Jan 03 1910 283.48 10 5 217 95 +- 6 Jan 03 2110 283.57 5 4 98 79 +- 8 Jan 04 0400 283.86 2 1 19 16 +- 4 ---------------------------------------------------
Solar longitudes refer to equinox J2000.0. nObs is the number of individual observing periods, nIND is the number of individual observers providing them, nQUA is the number of Quadrantids seen. The radiant position was assumed at alpha=230, delta=+49, the population index used was r=2.1. The expectation value of the ZHR,
ZHR = (1 + sum nQUA) / sum(Teff/C),
was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction. Times are rounded to the nearest 10 minutes.
information provided by:
Rainer Arlt and
Vladimir Krumov
(2001/01/04)
The 2000 return of this shower was eagerly awaited because an enhanced activity was expected. Indeed, the rates were significantly higher than the average. The last reported Ursid activity enhancement occurred on Dec. 22, 1996 at solar long. 270.7 with ZHR of the order of 30.
In 2000 the conditions were good as the Moon was almost new. The long northern nights allow a good overlap. Unfortunately, this first summary indicates that the most interesting period is not well covered. Most European observers had to finish around 6h UT (morning twilight). The number of North American data is scarce so far. As a consequence, we cannot yet achieve a good profile. Below find the preliminary data. The high ZHR at the end agrees with Japanese data published here before, although the errors are still quite large.
We are very grateful to the following 15 observers who sent in their reports in time for this first activity overview:
ARLRA Rainer Arlt (Germany)
BADPI Pierre Bader (Germany)
BUCAN Andreas Buchmann (Switzerland)
CANED Ed Cannon (USA)
ENZFR Frank Enzlein (Germany)
HOSDA Dave Hostetter (USA)
LANMA Marco Langbroek (Netherlands)
LUNRO Robert Lunsford (USA)
LUTHA Hartwig Luthen (Germany)
MOLSI Sirko Molau (Germany)
OSAKA Kazuhiro Osada (Japan)
PUNNI Nilesh Puntambekar (India)
RENJU Jurgen Rendtel (Germany)
STOEN Enrico Stomeo (Italy)
ZHUJI Jin Zhu (China)
------------------------------------------------------
Date Time (UT) Sollong nObs nIND nURS ZHR
------------------------------------------------------
Dec 22 0240 270.553 5 4 16 5.1 +- 1.2
22 0330 270.586 12 9 46 8.2 1.2
22 0410 270.620 16 9 76 12.7 1.5
22 0510 270.658 16 10 104 19.6 1.9
22 0535 270.676 8 6 58 26.1 3.4
22 0935 270.847 2 2 29 53 10
------------------------------------------------------
Solar longitudes refer to equinox J2000.0. nObs is the number of
individual observing periods, nIND is the number of individual
observers providing them, nURS is the number of Ursids seen. The
population index used was r=2.5. The expectation value of the ZHR,
ZHR = (1 + sum nURS) / sum(Teff/C),
was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction [sin (h_R)]. Times are rounded to the nearest 10 minutes.
information provided by:
Jürgen Rendtel
(2000/12/25)
The 2000 return of the strong shower reached its maximum under poor (moonlit) circumstances, restraining many observers from meteor watches. The currently available data show no unusual activity level or any peculiarities, but the near-maximum period is not (yet) well covered with data. So the list given below is a first, preliminary information only. Most observations were carried out under very poor skies. So a maximum correction factor of 7 was allowed, and all observations with the radiant more than 25 deg above the horizon were included. Although the (northern) nights are long and the radiant is above the horizon for (almost) the entire night, there are gaps which may become filled with further data. A list of observations was published by the NMS, but has not been included here at this stage.
We are very grateful to the following 17 observers who sent in their reports in time for this first activity overview:
DETPE Peter Detterline (USA)
GEOPE Petros Georgopoulos (Greece)
GLIGE George W. Gliba (USA)
GRALE Lew Gramer (USA)
KULRH Rhishikesh Kulkarni (India)
LI DO Dong Li (China)
LINMI Michael Linnolt (USA)
MCBAL Alastair McBeath (UK)
PUNNI Nilesh Puntambekar (India)
PURTU Tushar Purohit (India)
RENJU Jurgen Rendtel (Germany)
SHAJA Jason Shanley (USA)
SHASH Shashank Shalgar (India)
SPAGE George Spalding (UK)
TAIRI Richard Taibi (USA)
TRIJO Josep Trigo-Rodriguez (Spain)
WANSO Song Wanfang (China)
------------------------------------------------------
Date Time (UT) Sollong nObs nIND nGEM ZHR
------------------------------------------------------
Dec 13 0340 261.43 4 3 15 55 +- 13
13 0600 261.55 5 5 134 68 8
13 2000 262.12 3 3 24 118 20
13 2130 262.19 3 3 86 124 12
13 2240 262.24 3 3 102 126 11
14 0310 262.43 3 3 181 122 9
14 0850 262.67 1 1 10 79 24
14 2020 263.16 2 2 7 33 10
Solar longitudes refer to equinox J2000.0. nObs is the number of individual observing periods, nIND is the number of individual observers providing them, nGEM is the number of Geminids seen. The population index used was r=2.5. The expectation value of the ZHR,
ZHR = (1 + sum nGEM) / sum(Teff/C),
was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction [sin (h_R)]. Times are rounded to the nearest 10 minutes.
information provided by:
Jürgen Rendtel
(2000/12/18)
This minor shower is known to having produced short-lived activity peaks with ZHRs of the order of 30 to 40. Since this shower has not been monitored regularly until very recently, other outbursts may have been missed. In 2000 the conditions were good (almost New Moon).
According to observations in previous years, the peak period was expected near 18h UT (lambda = 158.6°) on August 31, 2000. Within the monitored intervals no unusual activity was reported, but there is still a gap in the available data between 158.0 and 158.7° (i.e. Aug 31, 3h UT and Aug 31, 20h UT). The highest rates occurred in the first period centered at 158.77°, but care must be taken because these ZHRs were obtained from European sites when the radiant elevation was around or even below 20° and are thus uncertain.
Intervals with the radiant being less than 15° above the horizon were not considered in the averages. However, there are no signs for unusual rates in these periods as well. Furthermore, video recordings and forward scatter data (Radio Observation Meteor Bulletin No. 85) also indicate a rather low activity of the alpha Aurigids in 2000.
We are very grateful to the following 15 observers who sent in their reports in time for this first activity overview:
ATAJU Jure Atanackov (Slovenia)
BUCAN Andreas Buchmann (Switzerland)
COOMA Mary Cook (UK)
DUBAU Audrius Dubietis (Lithuania)
ENZFR Frank Enzlein (Germany)
GEOPE Petros Georgopoulos (Greece)
GODSH Shelagh Godwin (UK)
JOHCA Carl Johannink (Germany)
KACJA Javor Kac (Slovenia)
LINMI Mike Linnolt (USA)
MCBAL Alastair McBeath (UK)
MCLNO Norman McLeod (USA)
RENJU Jurgen Rendtel (Germany)
WUSOL Oliver Wusk (Germany)
ZAKJU Jure Zakrajsek (Slovenia)
------------------------------------------------------
Date Time (UT) Sollong nObs nIND nAUR ZHR
------------------------------------------------------
Aug 29 0120 156.024 2 2 1 2.6 +- 1.8
31 0150 157.967 1 1 3 7.8 3.9
31 2130 158.770 3 2 7 10.4 3.7
31 2240 158.813 8 5 17 6.4 1.5
Sep 01 0030 158.884 7 5 12 3.1 0.9
01 0830 159.201 1 1 1 1.0 0.7
01 2330 159.781 10 6 21 3.3 0.7
Solar longitudes refer to equinox J2000.0. nObs is the number of individual observing periods, nIND is the number of individual observers providing them, nAUR is the number of Aurigids seen. The population index used was r=2.5. The expectation value of the ZHR,
ZHR = (1 + sum nAUR) / sum(Teff/C),
was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction. Times are rounded to the nearest 10 minutes.information provided by:
Jürgen Rendtel
(2000/09/07)
Apart from the traditional maximum at a solar longitude of 140.0 degrees, a pre-maximum peak has been observed for more than 10 years with variable strength. For the first time after the return of the parent comet 109P/Swift-Tuttle, the 2000 Perseids do not show this early peak.
The fresh Perseid peak was expected near 5h UT on August 12. The below Table gives a preliminary ZHR graph showing no significant maximum at this time. The traditional maximum of the Perseids was well pronounced in 2000. The peak time fell near a solar longitude of 140.0 degrees. The small number of observers covering the maximum allows us to give only a rough estimate of the amplitude of about ZHR=110-120.
We are very grateful to the following 49 observers who sent in their reports in time for this first activity overview:
ANDLU Luka Andrisic (Croatia) LISIR Irena Lisovski (Israel) ARLRA Rainer Arlt (Germany) LUTHA Hartwig Luthen (Germany) ATAJU Jure Atanackov (Slovenia) MAKVE Veikko Makela (Finland) BACNJ N.J. Bachmayer (Germany) MARAN Antonio Martinez (Venezuela) BARAS Asaf Barveld (Israel) MARJO Jose dos Reis Martins (Portugal) DEVMI Miha Devetak (Slovenia) MCBAL Alastair McBeath (UK) EINSH Shlomi Eini (Israel) MOLSI Sirko Molau (Germany) ENZFR Frank Enzlein (Germany) NAYAL Aliakbar Nayyeri (Iran) FESMO Mohsen Fesharaki (Iran) OSAKA Kazuhiro Osada (Japan) GLIGE George W. Gliba (USA) PALER Eric Palmer (USA) HALCA Cathy Hall (Canada) PARMO Mojahed Parsi (Iran) HASAM Amir Hassanzadeh (Iran) PERSU Suyin Perret Gentil (Venezuela) HASTA Takema Hashimoto (Japan) PEYNA Najmeh Peyvandi (Iran) HAVRO Roberto Haver (Italy) PLSMA Martin Plsek (Czech Republic) HEVZO Zoltan Hevesi (Hungary) RENJU Jurgen Rendtel (Germany) HODKE Ken Hodonsky (USA) SERMI Miguel A. Serra (Spain) HORKM Kamil Hornoch (Czech Rep.) SKOIV Skokic Ivica (Croatia) IVAMA Marko Ivanovic (Croatia) SWADA David Swann (USA) JERMA Maja Jeromel (Slovenia) TRIJO Josep Trigo-Rodriguez (Spain) KACJA Javor Kac (Slovenia) WUSOL Oliver Wusk (Germany) KHOSA Saedeh Khoshabadi (Iran) YOUKI Kim Youmans (USA) LEHMA Lehky Martin (Czech Rep.) YRJIL Ilkka Yrjola (Finland) LEUMA Marko Leustek (Croatia) ZAGDA David Zagorc (Slovenia) LEVAN Anna Levina (Israel) ZNOVL Vladimir Znojil (Czech Republic) LINMI Mike Linnolt (USA) --------------------------------------------------- Date Time (UT) Sollong nObs nIND nPER ZHR --------------------------------------------------- Aug 11 1840 139.378 11 8 263 40 +- 2 Aug 11 2100 139.472 15 13 88 37 +- 4 Aug 11 2200 139.512 19 15 192 57 +- 4 Aug 11 2300 139.552 17 16 248 55 +- 4 Aug 12 0000 139.592 22 18 387 55 +- 3 Aug 12 0100 139.632 28 21 796 69 +- 2 Aug 12 0200 139.672 24 20 709 75 +- 3 Aug 12 0330 139.728 3 3 78 84 +-10 Aug 12 0730 139.891 4 2 130 82 +- 7 Aug 12 0850 139.945 8 6 125 82 +- 7 Aug 12 0950 139.985 7 4 149 105 +- 9 Aug 12 1100 140.031 5 2 103 130 +-13 Aug 12 1500 140.191 6 2 200 62 +- 4 Aug 12 2240 140.498 10 3 64 29 +- 4 Aug 13 0220 140.644 6 4 55 28 +- 4 Aug 13 0650 140.824 11 3 178 48 +- 4 Aug 13 2210 141.438 4 2 20 18 +- 4 ---------------------------------------------------Solar longitudes refer to equinox J2000.0. nObs is the number of individual observing periods, nIND is the number of individual observers providing them, nPER is the number of Perseids seen. The radiant position was assumed at alpha=45, delta=+58, the population index used was r=2.0. The expectation value of the ZHR,
ZHR = (1 + sum nPER) / sum(Teff/C),
was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction. Times are rounded to the nearest 10 minutes.information provided by:
Rainer Arlt
(2000/08/16)
The excellent conditions with a New Moon on July 1 were used by many observers for monitoring the activity of the June Bootids despite activity was not expected to be extra-ordinary. Nevertheless, the detection of a weak, but distinct annual activity was a challenge for visual observing experts, too.
We are grateful to the following observers for the quick submission of data and careful shower association of their meteors:
ANTKA Karl Anthier (France) KACJA Javor Kac (Slovenia) ARLRA Rainer Arlt (Germany) LINMI Mike Linnolt (USA) ATAJU Jure Atanackov (Slovenia) LUNRO Robert Lunsford (USA) BOJEV Eva Bojurova (Bulgaria) MARPI Pierre Martin (Canada) BUCAN Andreas Buchmann (Switzerl.) MIHMI Mihail Mihov (Bulgaria) COOMA Mary Cook (UK) RASLI Lina Rashkova (Bulgaria) DECGO Goedele Deconink (Belgium) SAREL Elena Sarbinska (Bulgaria) GONRU Rui Goncalves (Portugal) STALE Leo Stachowicz (UK) HALCA Cathy Hall (USA) VELVA Valentin Velkov (Bulgaria) HAVRO Roberto Haver (Italy) VERJN Jan Verbert (Belgium) JOHCA Carl Johannink (Netherlands) YORYA Yordan Yordanov (Bulgaria)
In 1998, the June Bootids produced an outburst of activity with ZHRs near 80, possibly reaching 200, near a solar longitude of 95.7 degrees (J2000.0). The below Table gives an overview of the activity of the June Bootids in 2000. No outburst was observed. The apparent noise of ZHR values suggests a typical visual detection limit of minor showers near ZHR=1. Significant activity was therefore observed between June 27, 0400-2300 UT. This is about 0.3 to 0.8 degrees later (or 7 to 19 hours later) than in 1998. It will be worthwhile to revisit previous moon-free years to confirm an annual activity level of ZHR = 2 to 3.
The radiant position of the June Bootids was found to vary considerably during detections in previous years back to 1916. This could be a physical effect of orbital perturbations, but is strongly enhanced by a purely geometrical effect: As the meteoroids approach the Earth from behind, vectorial addition with the motion of the Earth is very sensitive to slightest orbital variations. (The reader may check this with vector parallelograms.)
Additional uncertainties are thus being introduced if the actual radiant position was not equal to what observers used for shower association. It is strongly suggested to send in the details on plotted meteors for a more thorough analysis. A first radiant analysis of data obtained by ARLRA, BOJEV, RASLI, SAREL, VELVA, MIHMI, YORYO in the observing camp at Avren, Bulgaria, delivers a distinct source at alpha=215, delta=+47. Whereas the radiant is sharply defined at its western edge, a "tail" of convergences extends towards east from this position. The radiant position is corrected for zenithal attraction and diurnal aberration.
--------------------------------------------------------- Date Time (UT), avg. Sollon nObs nIND nJBO ZHR +- --------------------------------------------------------- Jun 26 2300-0650 0250 94.81 6 3 2 1.3 0.8 Jun 26 2100-2300 2200 95.57 5 5 2 0.8 0.5 Jun 27 2300-0252 0040 95.68 9 5 4 1.3 0.6 Jun 27 0400-1102 0730 95.95 5 2 8 3.6 1.2 Jun 27 2010-2300 2135 96.51 10 8 14 1.9 0.5 Jun 27 2300-0020 2340 96.59 9 9 2 0.6 0.3 Jun 28 0300-0740 0520 96.82 6 2 4 1.2 0.6 Jun 28 2020-0100 2240 97.51 8 6 1 0.4 0.3 Jun 29 2010-2330 2150 98.43 4 3 0 0.4 0.4 ---------------------------------------------------------
Solar longitudes refer to equinox J2000.0. nObs is the number of individual observing periods, nIND is the number of individual observers providing them, nJBO is the number of June Bootids seen. The the radiant position was assumed at alpha=224, delta=+48, the population index used wa r=2.2 as derived from the outburst in 1998. The extremely low meteor numbers require a careful statistical treatment. For a given meteor number, various true rates would have been possible. The expectation value of the ZHR is, therefore, the average of all these rates (the integral over the distribution function) which are naturally all greater than or equal to 0. The resuls is most obvious in the last row (June 29): 0 meteors could have been caused by ZHRs between 0.0 and 0.8. The longer the observers keep seeing 0 meteors, the lower the expectation value for ZHR. The actual small-number ZHR formula is
ZHR = (1 + sum nJBO) / sum(Teff/C),
where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction. Zenith attraction was not taken into account here; most of the observing periods had radiant elevations hR>40 degrees.
information provided by:
Rainer Arlt
(2000/07/04)
The large number of observing reports coming in after the first Shower Circular about the eta-Aquarids allowed an update of the activity graph. The shower appears to exhibit a period of about three days with ZHRs above 50. The data set does not allow to conclude about the fluctuations; yet the broad maximum and the maximum ZHR of ~60 are a clear result of this preliminary compilation based on the reports of the following observer:
ATAJU Jure Atanackov (Slovenia) BUCAN Andreas Buchmann (Switzerland) CERJA Jakub Cerny (Czech Republic) COOTI Tim Cooper (South Africa) DAVMA Mark Davis (USA) DIAAS Asdai Diaz Rodriguez (Cuba) HOLDA David Holman (USA) JOHCA Carl Johannink (the Netherlands) KONKH Khalil Konsul (Jordan) KOUWE Wen Kou (China) LANMA Marco Langbroek (the Netherlands) LINMI Mike Linnolt (USA) MARAD Adam Marsh (Australia) MARPI Pierre Martin (Canada) MATMI Michael Matiazzo (Australia) MCLAL Alex M'clintock (Spain) MISKO Koen Miskotte (the Netherlands) MOLSI Sirko Molau (Germany, from Jordan) MOSSC Scott Moser (USA) MOTER Erick Mota Perez (Cuba) NATSV Sven Nather (Germany, from Morocco) NITMI Mirko Nitschke (Germany, from Jordan) TELKH Khaled M. Tell (Jordan) YOUKI Kim Youmans (USA) -------------------------------------------- Date Time (UT) Sol. nETA nObs <ZHR> +- -------------------------------------------- Apr 29 1800 39.71 1 2 2.4 1.7 Apr 30 1740 40.67 18 4 18 4.1 May 01 2210 41.82 34 5 28 4.6 May 03 0050 42.90 33 4 36 6.1 May 04 0520 44.05 15 4 36 8.9 May 04 1820 44.58 17 5 54 13 May 05 0040 44.84 64 8 65 8.0 May 05 1330 45.35 86 6 48 5.2 May 06 0140 45.84 105 11 56 5.4 May 06 0840 46.13 35 7 35 5.9 May 06 1610 46.43 119 6 51 4.7 May 07 0630 47.01 61 8 38 4.8 May 08 0630 47.98 57 4 60 7.8 May 10 0210 49.73 23 4 24 5.0 May 11 0120 50.67 4 2 26 12 --------------------------------------------
Solar longitudes refer to equinox J2000. Average times are given with 10-minute accuracy though often refer to many hours coverage. The average ZHR was computed by <ZHR> = sum n / sum(Teff/C) where Teff is the effective observing time, C is the total correction according to limiting magnitude, possible field obstruction and radiant elevation as sin(hR). The ZHR refers to a limiting magnitude of +6.5 and a radiant elevation of 90 degrees. nETA is the number eta-Aquarids seen, nObs is the number of observing periods contributing to the average; the number of individual observers is smaller in most of the cases.
information provided by:
Rainer Arlt
(2000/05/18)
The meteor shower of the eta-Aquarids is not easily observed from mid-northern latitudes where the majority of visual observers is located, because of the very late rising of the radiant before dawn, and fewer amateurs are observing from the southern hemi- sphere where dawn is much later, and the radiant climbs higher before the end of the meteor watch.
It is therefore even more challenging to produce a meaningful activity graph of the eta-Aquarids quickly after their maximum, and I am very grateful for the immediate submission of the reports by the following observers:
DAVMA Mark Davis (USA) JOHCA Carl Johannink (the Netherlands) LANMA Marco Langbroek (the Netherlands) LINMI Mike Linnolt (USA) MARAD Adam Marsh (Australia) MARPI Pierre Martin (Canada) MATMI Michael Matiazzo (Australia) MCLAL Alex M'clintock (Spain) MISKO Koen Miskotte (the Netherlands) MOSSC Scott Moser (USA) YOUKI Kim Youmans (USA)
The gradual increase of activity is nicely show in the below Table. The maximum time is, however, hard to fix because of a severe dip in the UT morning of May 6 when the ZHR fell below half-value of its neighbours. Maximum ZHRs appear to be at the lower end of previous years' typical values of 60-70 per hour.
-------------------------------------------- Date Time (UT) Sol. nETA nObs <ZHR> +- -------------------------------------------- Apr 29 1800 39.71 1 2 2.4 1.7 Apr 30 1640 40.63 2 1 20 11 May 01 1730 41.64 25 3 24 4.8 May 03 0050 42.90 23 4 36 6.1 May 04 0840 44.19 15 3 38 9.5 May 04 1750 44.56 14 4 50 13 May 05 1330 45.35 80 5 49 5.5 May 06 0530 46.00 12 5 24 6.8 May 06 1610 46.43 119 6 51 4.7 May 07 0530 46.96 19 4 25 5.7 --------------------------------------------Solar longitudes refer to equinox J2000. Average times are given with 10-minute accuracy though often refer to many hours coverage. The average ZHR was computed by <ZHR> = sum n / sum(Teff/C) where Teff is the effective observing time, C is the total correction according to limiting magnitude, possible field obstruction and radiant elevation as sin(hR). The ZHR refers to a limiting magnitude of +6.5 and a radiant elevation of 90 degrees. nETA is the number eta-Aquarids seen, nObs is the number of observing periods contributing to the average; the number of individual observers is smaller in most of the cases.
information provided by:
Rainer Arlt
(2000/05/08)
Observations of the 2000 Lyrids were hampered by a gibbous waning Moon, which rose before midnight shortly after the radiant of the Lyrids had reached altitudes above 30 degrees. Typically, the annual maximum of the Lyrids falls between solar longitudes 32.1 deg and 32.5 deg, corresponding to April 21, 22:10 UT to April 22, 05:40 UT this year.
The return of the Lyrid meteor shower in 2000 was normal, according to the present information. The amount of data available is far from conclusive. High ZHRs of roughly 15 to 20 were recorded all through the (UT) evening of April 21 and the whole morning of April 22. We would like to thank the following observers for their quick reports after the observation:
ARLRA Rainer Arlt (Germany) ATAJU Jure Atanackov (Slovenia) BUCAN Andreas Buchmann (Switzerland) DIAAS Asdai Diaz Rodriguez (Cuba) DUBAU Audrius Dubietis (Lithuania) ENZFR Frank Enzlein (Germany) HANIS Isabel Handel (Germany) KACJA Javor Kac (Slovenia) LINMI Mike Linnolt (USA) OSAKA Kazuhiro Osada (Japan) PETNA Natasa Petelin (Slovenia) RENJU Jurgen Rendtel (Germany) TRIJO Josep M. Trigo (Spain) WUSOL Oliver Wusk (Germany) YOUKI Kim Youmans (USA) YRJIL Ilkka Yrjola (Finland) ------------------------------------------------------------------------- Date UT Sollong nLYR nObs ZHR +- Remarks ------------------------------------------------------------------------- April 21 02:00 31.28 3 1 5.4 3.1 April 21 20:00 32.01 55 9 17 9 April 22 01:20 32.23 31 5 12 5 April 22 08:30 32.52 16 5 20 10 low LM for two indiv. values April 22 21:00 33.02 29 11 7.0 5.0 April 22 22:50 33.10 17 6 8.3 3.7 -------------------------------------------------------------------------
Solar longitudes refer to equinox J2000. ZHRs are based on a population index of r=2.9. Errors are standard deviations of the averages except for the first value based on a single observation where we give ZHR/sqrt(nLYR).
information provided by:
Rainer Arlt
(2000/04/25)