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Perseids 2000 over the UK and elsewhere

By Alastair McBeath, SPA Meteor Section Director

Introduction

The 2000 British summer, though significantly cooler and wetter in many parts than for some years, produced some better skies right on cue for the Perseids. Indeed in SPA Meteor Section (SPAMS) data, only 4 of the 25 nights from July 19-20 to August 12-13 inclusive produced no visual meteor reports, a situation virtually unique for at least the past 17 years!

Since the preliminary Perseid report was issued on this Webpage in 2000 August, more observations have arrived, and additional analyses have been carried out, including an examination of the radio data submitted to the SPAMS, and a detailed report by Rainer Arlt and Isabel Haendel of the International Meteor Organization (IMO) on the near-maximum Perseid visual results collected by 131 observers around the globe (published in WGN, the Journal of the IMO 28:5 (2000 October), pages 166-171). The revised report given here adds to and amends the earlier information about how the Perseids behaved in 2000 July-August.


The Observers

The list of observers active in July and August follows, and as normal, includes those who reported successful watches, and those whose efforts were thwarted by clouds but who still troubled to send in details. Visual observers in England have no additional notes given. Those elsewhere are listed with the country they observed from. Non-visual observers are denoted by the letters "P" = photographic, "R" = radio, or "V" = video. A "+" sign before the letter indicates the observer also carried out visual watching. Of the radio reports, all the data except that from the team led by Albert Heyes were provided by Chris Steyaert in Radio Meteor Observation Bulletins 84-86 inclusive, dated August to October 2000 respectively (contact e-mail: steyaert@vvs.be, Website: http://page.to/rmob/). The German Arbeitskreis Meteore (AKM) data were chiefly taken from their journal Meteoros 3:8-9 and 3:10 (2000) submitted by Ina Rendtel. The Iranian results were forwarded to us by Mohammad Ali Khodayari.

AKM members (all in Germany, except where noted): Rainer Arlt, Pierre Bader, Lukas Bolz, Frank Enzlein, Mathias Growe, Andre Knoefel (V), Daniel Koehn, Detlef Koschny (Netherlands; V), Hartwig Luethen, Sirko Molau (+V), Sven Naether, Mirko Nitschke (V), Ina Rendtel (Austria and Germany), Juergen Rendtel (+V, P), Joerg Strunk (V, P), Roland Winkler, Nikolai Wuensche, Oliver Wusk (Germany and Sweden); Enric Fraile Algeciras (Spain; R), Eva Bojurova (Bulgaria; including reports from two Astroclub Canopus observing camps) Mike Boschat (Canada; R), Julie Brandon, Jay Brausch (North Dakota, USA), Michael Brooke, Mary Cook, Maggie Daly, Maurice de Meyere (Belgium; R), Clive Down (Wales), Steve Evans (Spain), Guy Fennimore (Wales), Elham Ghanbarian (Iran), Ghent University (Belgium; R), Shelagh Godwin, Valentin Grigore (Romania), Philip Heppenstall (England and France), Zoltan Hevesi (Hungary), Albert Heyes (R; with John Blakeley and Jim Leviston), Will Kelsey (Arkansas, USA; R), Werfried Kuneth (Austria; R), Jeff Lashley (Scotland; V), Bob Lunsford (California, USA), Tony Markham, Alastair McBeath, Tom McEwan (Scotland), Shefteh Mihanyar (Iran), R B Minton (New Mexico, USA; R), Sadao Okamoto (Japan; R), Trevor Pendleton, Mohammad Ali Rahmani (Iran), Layla Rostami (Iran), Ton Schoenmaker (Netherlands; R), George Spalding, Dave Swan (R), Pierre Terrier (France; R), Garfield Tsao (Taiwan; R), Ilkka Yrjola (Finland; R).


Shower Overview

per2000-1-3.jpgAlthough severe problems were anticipated in covering the Perseid maxima in 2000 because of the bright waxing gibbous Moon, full on August 15, enthusiasm among watchers was high right over the shower's best. Three peaks on August 12 were possible from recent returns. The primary maximum was expected around 05h UT, but was not found in the IMO investigation. This peak had shown marked signs of declining from its highest Zenithal Hourly Rates (ZHRs) of 400+ over Japan in 1991, to ~ 100-110 by 1998-99, and was also occurring somewhat later each year, which was beginning to blend it in with the secondary or "traditional" maximum. This blending may have continued in 2000, as the secondary peak produced rather stronger rates than for some years in the IMO data, with a ZHR of ~ 125 +/- 15 around 09h30m UT, marginally earlier than anticipated (predicted for ~ 10h UT). A tertiary peak, first noted in 1997, was expected to occur near 19h UT, but there is a gap in the IMO observations then. A slight resurgence raising ZHRs from ~ 40 +/- 5 to 60-65 +/- 5 happened between roughly 22h-00h UT on August 12-13, but it is not clear how important this may have been.

Radio results were hampered by various forms of interference all summer, most notably by some exceptionally severe Sporadic-E events throughout May-August, but the chief problem over the Perseid maxima was a huge auroral storm on August 12! Visual observers in North America were able to enjoy the unusual spectacle of this superb, if moonlit, storm as a backdrop to the best from the Perseids, though regrettably the combined effects of the Moon and auroral light often meant only the brightest Perseids remained visible. There is a weak confirmation of the visual Perseid peak timing in the radio reports, but too many operators were unable to detect much except noise all day.

The accompanying graph shows how SPAMS Perseid mean ZHRs were recorded from when Perseid numbers were high enough to compute reliable rates on July 26-27, until August 13-14, although the first swift-flying Perseid meteors were noted in even casual sky-checks from about a week before this July date, much as normal. The ZHRs from August 9-10 to 13-14 especially suffered problems because of increasingly strong moonlight, which persisted until almost the start of morning twilight from Britain by August 11-12. When August's full Moon had waned sufficiently for observing to recommence, Perseid rates had dropped well back, with ZHRs on August 19-20 averaging 7 +/- 5.

Using better-sky data from July and August, where less than 20% cloud cover was present, and the sky's limiting magnitude was at least +5.5 (this latter parameter relaxed to +5.0 or better for the moonlit period near the Perseid peaks), corrected mean magnitudes for the Perseids and July-August sporadics of +2.3 (487 meteors) and +3.5 (324 meteors) were computed respectively. The bar-graph here illustrates the full magnitude distribution, while the graph below it gives details for the persistent trains seen during the same period. Such ionization trains were left by 34.4% of Perseids and just 1% of sporadics (not shown in the graph as too few were seen) during the summer.

 


Observers' Reactions Near the Perseid Peak

Correspondence from UK watchers shows much of England enjoyed a good night on August 11-12 in spite of the Moon, with only thin, typically hazy, cirrus clouds reported, though these were quite widespread. Limiting magnitudes with the Moon still up were around +4.9 to +5.3 at best, but a few people were lucky in getting a +5.5 sky briefly between moonset and morning twilight. As often happens near Perseid maximum, several watchers were tempted into continuing their observing into too-strong twilight, still spotting occasional bright Perseids until just an hour before sunrise in one case.

English observers seemed generally pleased with their night's work on August 11-12, though as Rainer Arlt in Germany also noted, a little clearer sky would have been even better. Perseid rates were good without being spectacular, as veteran George Spalding commented, echoing the thoughts of other experienced meteor watchers, which suggested the best was still to come after dawn over Europe. Plenty of bright Perseids (magnitude +2 or brighter) were seen, but fireball gems were relatively rare, the brightest of magnitude -6, a blue-green-violet event at 00h37m UT on August 12, which produced two flares and a 13-second long persistent train.

In North America, where some of the highest Perseid rates were seen this year, Bob Lunsford remarked that the impressive meteor display was scarcely dimmed by a layer of smoke over his usually excellent Californian sky, the smoke due to the horrendous, extensive, forest fires all across the western USA. Thankfully, there were no casualties among our North American meteor observing colleagues because of these fires, though most unfortunately, R B Minton's radio set-up was wrecked in a lightning strike during a storm on August 27. Bob Lunsford mentioned the smoke layer concealed any sign of the auroral activity which was spotted from numerous other sites in North America coincident with the Perseids' best, though people at less smoke-influenced locations in California did see this wonderful auroral storm.

Eva Bojurova reported the Bulgarian "Astroclub Canopus" watchers had a very successful observing camp at Avren from July 24th to August 5th, mainly concentrating on the various Aquarid-Capricornid showers. They then returned to Kamen Bryag on the Black Sea coast to celebrate the first anniversary of the total solar eclipse beautifully witnessed from there on 1999 August 11. Their 2000 Perseid peak observing was less fortunate, as overcast skies appeared nicely in time for moonset on August 11-12!


Conclusion

The Perseids continue to provide fascinating new features, even at a Moon-affected return like that in 2000. Theoretical calculations suggested the disappearance of the primary maximum was most likely in 2001-2002, but it seems from the 2000 return it has faded away somewhat sooner than expected. However, the same calculations also indicated its activity could revive again in 2004-2006, which will no doubt help keep the Perseids as one of the meteor observers' favourite showers.

Many thanks go to all the observers and correspondents who have provided the details to make this report possible. Clear skies for your next watches!

The 2000 British summer, though significantly cooler and wetter in many parts than for some years, produced some better skies right on cue for the Perseids. Indeed in SPA Meteor Section (SPAMS) data, only 4 of the 25 nights from July 19-20 to August 12-13 inclusive produced no visual meteor reports, a situation virtually unique for at least the past 17 years!

Since the preliminary Perseid report was issued on this Webpage in 2000 August, more observations have arrived, and additional analyses have been carried out, including an examination of the radio data submitted to the SPAMS, and a detailed report by Rainer Arlt and Isabel Haendel of the International Meteor Organization (IMO) on the near-maximum Perseid visual results collected by 131 observers around the globe (published in WGN, the Journal of the IMO 28:5 (2000 October), pages 166-171). The revised report given here adds to and amends the earlier information about how the Perseids behaved in 2000 July-August.

Alastair McBeath, SPA Meteor Section Director. vice_president@imo.net

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