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An SPA Meteor Section Special Report
Up to two storm-strength maxima were predicted for the badly moonlit Leonids in 2002, and as with the 2001 double-peaked storm, the shower did not disappoint the fortunate watchers with clearer skies. Unlike in 2001 though, British observers were not only favourably placed to catch one of the storm peaks under night-time skies, but also were luckier with the weather, and many people were able to see something near the shower's best from here. This report provides details on how the visual observers enjoyed the event, along with information on how the storms were recorded by radio and imaging results. Moonlight and poor weather meant too few visual and video datasets were available from nights other than November 18-19 during the Leonids to make a sensible analysis of them practical, so here we concentrate on looking at results from near the peaks only. While the Moon hindered visual observers, the storm level meteor rates survived remarkably well.
As usual, the essential element in these reports is the numerous dedicated meteor watchers and casual witnesses, who troubled to observe and provided data to us from 2002 November 16-17 to 20-21 (most from November 18-19), including those who were unlucky with their sky conditions. Very many most grateful thanks go the list of people below for their work during the 2002 Leonids. Additional thanks for provision of often extensive data summaries go to: Bob Lunsford of the American Meteor Society (AMS - website: http://www.amsmeteors.org) via the AMS's journal Meteor Trails No.18 (March 2003); Ina Rendtel of the German Arbeitskreis Meteore group (AKM; data in their journal Meteoros 5:12 (2002) and 6:1 (2003) - website: http://www.meteoros.de); and Chris Steyaert, editor of the Radio Meteor Observation Bulletins (RMOBs - website: http://www.rmob.org), with data from numbers 112 and 113, November and December 2002 respectively. In the listing, observers whose data was taken chiefly from the one of these sources are credited with the appropriate abbreviation. Other letters indicate the type of observing undertaken, including "P" = photographic results, "R" = radio observations, "Vi" = video data and "+ V" = "and visual results". Those not otherwise noted provided visual reports.
Enric Fraile Algeciras (RMOB, Spain; R), Ardalan Alizadeh (AMS, Iran), Rainer Arlt (AKM, France), Dirk Artoos (Belgium; R), Jure Atanackov (AMS, France), Daniel Bailey (AMS, Illinois, USA), Kacem Bankih (AMS, Algeria), Colin Begg (Scotland), Abdellah Bekkaye (AMS, Algeria), Leslie Bell (AMS, Virginia, USA), Larry Black (AMS, Iowa, USA), Lukas Bolz (AKM, France), Mike Boschat (RMOB, Nova Scotia, Canada; R), Walter Boschin (RMOB, Italy; R), Jay Brausch (North Dakota, USA), Paul Brierley (England), David Briggs (England), Jeff Brower (RMOB, Colorado, USA; R), Dave Campbell (England), Ed Cannon (AMS, Texas, USA), Laverne Castillo (AMS, Virginia, USA), Cui Chenzhou (AMS, China), Diane Cherry (Scotland), Alessandro Ciano (AMS, France), Paul Clark (England), Si Clarke (England), Douglas Clayton (AMS, Virginia, USA), Russell Cockman (Scotland; P + V), Mike Collins (England), Heather Couper (England), Mike Dale (Scotland), Maurice de Meyere (RMOB, Belgium; R), Parag Deotare (AMS, India), Mario di Maggio (Scotland), Gina Donohue (England), Matt Donohue (England), Peter Duffy (England), David Entwistle (England; P, R + V), Anita Evans (England), Steve Evans (Spain; Vi + V; video summary also in Meteoros 6:12), Didier Favre (RMOB, France; R), Mike Feist (England), Guy Fennimore (England), Dave Gavine (Scotland), Valter Gennaro (RMOB, Italy; R), P Georgopoulos (AMS, Greece), Christoph Gerber (AKM, Germany), Ghent University (RMOB, Belgium; R), Andrei Dorian Gheorghe (Romania; who also provided notes on observations by others in Romania, including group leaders: Stefan Berinde, Alexandru Conu, Valentin Grigore, Dan Mitrut, Raul Truta, Cristina Tinta Vaas, and individuals: Virgil Chiriac, Gabriel Ivanescu, C Matei, Emil Neata, Teodora Plaesu, Gelu Claudiu Radu), George Gliba (AMS, West Virginia, USA), Shelagh Godwin (England), Darja Golikowa (AKM, France), Glen Gorsuch (AMS, Wisconsin, USA), Valentin Grigore (Romania), Patrice Guerin (RMOB, France; R), Rafael Haag (RMOB, Brazil; R), Walter Haas (AMS, New Mexico, USA), Meredic Hallett (Wales), Steve Hansen (RMOB, Massachusetts, USA; R), A Hassanzadeh (AMS, Iran), Robert Hays (AMS, Illinois, USA), Chris Heapy (England), Craig Heden (AMS, California, USA), Nigel Henbest (England), Mike Holmes (Scotland), Terry Holmes (England), Chris Holt (England), Martin Hoerenz (AKM, Canary Islands), James Hyder (AMS, Maryland, USA), Adrian Jannetta (England), Steve Jaworiwsky (AMS, Maryland, USA), Edwin Jones (AMS, Arkansas, USA), Paul Jones (AMS, Florida, USA), Javor Kac (AMS, France), Gene Kispert (AMS, Minnesota, USA), Nigel Knighton (England), Andre Knoefel (AKM, Spain), Ralf Koschack (AKM, Germany), Detlef Koschny (AKM, Spain), Michael Krocil (RMOB, Czech Republic; R), Gary Kronk (AMS, Illinois, USA), Michael Lacombe (AMS, Maine, USA), Peter Lawrence (England), Thomas Lazuka (AMS, Illinois, USA), Robin Leadbeater (England; Vi, P + V), Bob Lunsford (airborne between southern Europe and the USA, with the NASA MAC Leonid teams), Hartwig Luethen (AKM, Canary Islands), Xiaoyun Ma (AMS, China), G Maravelias (AMS, Greece), Tony Markham (England), Nick Martin (Scotland), Pierre Martin (AMS, Florida, USA), Felix Martinez (AMS, North Carolina & Virginia, USA), Paul Martsching (AMS, Arizona & Iowa, USA), Bert Matous (AMS, Kansas, USA), Alastair McBeath (England), Tom McEwan (Scotland), Jim McGraw (AMS, Iowa, USA), Banouh N Mefnoun (AMS, Algeria), Cliff Meredith (England; P + V), Toshihide Miyake (RMOB, Japan; R), Sirko Molau (AKM, Germany; Vi), Naoki Moriwaki (RMOB, Japan; R), Michael Morrow (AMS, Hawaii, USA), Selina Mueller (AKM, France), Sven Naether (AKM, Canary Islands), Stan Nelson (RMOB, New Mexico, USA; R), Ben Notarianni (England), Robert Obraz (RMOB, Croatia; R), Hiroshi Ogawa (RMOB, Japan; R), Sadao Okamoto (RMOB, Japan; R), Guy Ottewell (England), Cedric Peinado (AMS, France), Peter Phillips (Northern Ireland), Nilesh Puntambekar (AMS, India), Ankur Puranik (AMS, India), Steve Quirk (AKM, Australia; Vi), Rabat Astronomical Observatory (Morocco; 33 visual observers' data was summarised by Hamid Touma of the Observatory in a report kindly forwarded by Andrei Dorian Gheorghe; the observers were: Mamoune Alaoui, Catherine Almouatamid, Ka Bencheikr, Nessrine Bencheikr, Mariem Benkirane, Younes Ben Otmane, Amine Boubnane, Foudil Chakib, Fouad Elamrani, Chakib El Kabbaj, Mohamed Amine El Kabbaj, Hanane El Khadri, Ali El Khedri, Tarik El Mellouki, Ahmed Graigaa, Amine Graigaa, Mohamed Hakam, Ilharne Jemmah, Amal Kadiri, Reda Kadiri, Samir Kadiri, Noudine Laghrissi, Abdelkrim Lyazidi, Abdelkrim Lyazidi (two watchers with the same name), Annyssa Lyazidi, Chaymae Lyazidi, Ghita Lyazidi, Youssef Lyazidi, Rachid Maaninou, Anas Medkouri, Bachir Nsiri, Naoufal Rih, Hamid Touma), F A R Ramirez (AMS, Canary Islands), Ingo Reimann (RMOB, Germany; R), Juergen Rendtel (AKM, Canary Islands; Vi + V), Petra Rendtel (AKM, Canary Islands), Gilberto Klaar Renner (Brazil; R), Morgan Renner (AMS, Wyoming, USA), Paul Richardson (England), David Riggs (AMS, Virginia, USA), Ian Rigney (England), Vanya Rodiger (Croatia), Robert Savard (RMOB, Quebec, Canada; R), Robin Scagell (France), Sally Scagell (France), Ton Schoenmaker (Netherlands; R; data also in RMOB 112), Walter Scott Jr. (Scotland), M Seyyednezhad (AMS, Iran), Jonathan Shanklin (France), Caroline Shelnut (AMS, Virginia, USA), Karl Simmons (AMS, Florida, USA), George Spalding (England), Roger Stapleton (Scotland), Chris Stephan (AMS, Florida), C Stevenson (AMS, Newfoundland, Canada), Craig Stobo (Scotland), Enrico Stomeo (Italy), Paul Sutherland (France), Dave Swan (RMOB, England; R), David Swann (AMS, Texas, USA), Rich Taibi (North Carolina, USA; data summaries also in Meteor Trails 18), Mustapha Tellai (AMS, Algeria), Istvan Tepliczky (RMOB, Hungary; R), Pierre Terrier (RMOB, France; R), Rocky Togni (AMS, Arkansas, USA), Stanley Toyn (England), Mihaela Triglav (Slovenia), Yung Cheich Tsao (RMOB, Taiwan, China; R), Hendrik Vandenbruaene (Belgium), Jan Verbert (France), Roy Watson (Scotland), Sarah Watson (Scotland), Chris Wilson (Scotland), Roland Winkler (AKM, Germany), Paul Wolstenholme (England), Oliver Wuesk (AKM, Queensland, Australia), Kim Youmans (AMS, Georgia, USA), Bruce Young (RMOB, Queensland, Australia; R), Ilkka Yrjola (RMOB, Finland; R), Jure Zakrajsek (AMS, France), Joseph Zammit (AMS, Malta).
In the Section's Leonids 2001 Special Report on this website, some of the problems in computing zenithal hourly rates (ZHRs) from times of very high meteor activity were discussed, where observers may struggle to give accurate magnitude distributions during phases of storm activity, in turn leading to the calculation of less accurate estimated ZHRs than normal. This year, although more observers were able to provide magnitude details, even during the storm peak heights, moonlight seriously affected the sky limiting magnitudes (LMs). In order to keep reasonable numbers of meteors in the magnitude and ZHR analyses, the usual strictures regarding LMs were relaxed from +5.5 or better, to +4.0 or better. This means the ZHRs still give a useful guide to the general character and relative strengths of the activity seen at different times, but are less reliable for the specific numbers involved. This relaxation in the LM criterion meant an assumed "population index", r, had to be used, instead of that normally calculated from the observed magnitude distributions. The r-value was taken as 2.5. There are indications in the International Meteor Organization (IMO) results (website: http://www.imo.net) that this is probably a good mean value for the 2002 Leonids as a whole. However, before the first peak, it may have been nearer 1.9-2.1 (meaning more bright meteors were present), and shortly before the second maximum it may have been about 3.1-3.4 (indicating a lot more faint meteors than expected), improving to 2.7-2.8 during the second peak itself. As in 2001, the ZHRs discussed here were derived using 5-15 minute intervals to help give a better picture of any briefer changes in activity, and the main maxima timings. Again, these shorter intervals reduce the numerical accuracy of the final results, but provide a better view of what happened and when. The results presented here are still generally reliable in demonstrating what the 2002 Leonids produced.
We begin with a percentage magnitude distribution histogram for the Leonids overall and during three main intervals on November 18-19, before, during to soon after the main European peak, and in the period after this, covering the main North American maximum. Values for the sporadics are also shown, along with the corrected mean magnitude values for all these intervals and sources. In total 930 Leonids, but just 45 sporadics, are represented. Most meteors were reasonably bright (or they would not have survived the moonlight!), so the distributions are not what we would normally expect. For instance, in 2001 50% of the Leonids were magnitude +2 or brighter, and about 25% of the sporadics. In 2002, the respective values were nearer 75% and 50%. The Leonid mean magnitudes decreased over time, and there is an indication that somewhat more fireballs were seen before the first maximum than subsequently. The faintest mean magnitude covering the second storm maximum is in-line with the IMO findings of many more faint meteors during that later peak. The small number of sporadic magnitude estimates gives their details less reliability, although the overall character of the distribution graph is fairly typical of what we would expect.
The first two ZHR graphs show the activity across both storm maxima on November 18-19, derived from 27,585 Leonids seen in almost 348 hours of watching. The first graph uses a linear ZHR axis, and indicates the short, sharp nature of both maxima compared to the lower activity away from them. The second graph, this time with a logarithmic y-axis, allows some detail in the activity away from the main peaks to be appreciated. This includes the fact that the typical Leonid ZHRs of around 10-15, seen for many years prior to the late 1990s, when rates began to rise towards the shower's near-millennial storms, would scarcely have registered this time! Note the steep outer curves in the approach to the first storm peak, and in the departure from the second, while the inner curves are somewhat more gentle. ZHRs were above 100 virtually throughout the whole interval these graphs represent, although parts of the dip between roughly 06h-08h30m UT were not well-covered, a "North Atlantic gap" between the last European observations near dawn, and the majority of North American watchers starting to enjoy a useful Leonid radiant elevation.
The next two graphs close-in on the two storm maxima, each using a linear y-axis. The first maximum reached its highest ZHR of 3180 +/- 80 at 04h05m +/- 5 min UT, with a Full Width Half Maximum, FWHM, time (during which rates were above half the highest value) of 44 min +/- 5 min between 03h52m-04h36m UT. The preliminary IMO data, drawing on roughly twice the number of meteors available for the SPAMS analysis, indicated a peak at 04h08m +/- 1 min UT, ZHR = 2505 +/- 55, FWHM = 39 min +/- 3 min. The second peak in SPAMS data was achieved at 10h45m +/- 5 min UT, ZHR = 2640 +/- 110, FWHM = 35 min +/- 5 min (10h27m-11h02m UT), although near-peak rates appear to have been sustained at only slightly reduced levels until 10h55m UT (ZHRs around 2300-2450). In IMO results, this second peak showed the following characteristics: time = 10h46m +/- 1 min UT; ZHR = 2940 +/- 210; FWHM = 25 min +/- 3 min. The IMO's second peak was computed assuming more faint meteors were present than in the SPAMS analysis, and also does not show the extended nature of the maximum rates suggested here nearly as well, though ZHRs were still 2250 +/- 160 by 10h50m UT.
It is difficult to be sure if the "shoulder" of near-constant rates seen both after the first maximum, between roughly 04h15m-04h30m UT, and before the second, around 10h30m- 10h40m UT were real effects in the shower, or simply artefacts in the analysis. The number of observations available during these times gives some confidence that they were genuine features however.
The relative strengths of the two maxima remain open for debate. This analysis, assuming a constant r-value throughout, implies the European or first peak was the stronger, while the IMO data allowed the estimation of the probable change in r during the 2002 Leonids, which indicated the North American or second peak was stronger. Judging by some of the observers' comments from North America, whatever the actuality, the impression was that the Leonid peak there was not as impressive a storm as seen in 2001. This could be the case if meteor rates were actually lower, or if they seemed lower because many meteors during the storm were faint, too faint to be seen in the bright moonlight.
Echoing the 2001 results once more, relatively few Leonid meteor train reports were secured. Part of the reason was that observers rightly concentrated on getting accurate magnitude distributions during the storm, but part was down to the poor sky conditions. Faint trains, like faint meteors, do not show up well on a moonlit night. In 2002, about 58% of Leonids from the magnitude distributions had the presence or absence of trains noted, compared with 78% of sporadics (but remember that few sporadics were seen anyway), yielding train populations of 29% and 6% respectively. While the sporadic value is typical for them overall, the lower Leonid one reflects the expected problems. Too few train reports were received during the North American maximum to say if the potentially greater numbers of faint meteors then might have reduced the train proportion still further.
The six graphs here give a representative sample of the radio observations received from the various geographic regions around the world - Australia (Bruce Young), Japan (Toshihide Miyake), East Asia (Yung Cheich Tsao on Taiwan, who as the most westerly of the Far Eastern observers was just able to catch something of the first storm peak as the radiant was getting ready to set for him), Europe (Ton Schoenmaker, whose results were corrected for the amount of time lost to his receiver being saturated with meteor echoes during the higher activities), South America (Gilberto Klar Renner, in which a log y-axis scale has been used in order not to lose the lesser detail in the lower count times away from the Leonid storm. His system was only operational from midnight UT on November 17) and North America (Stan Nelson).
Each graph gives hourly counts of meteor echoes reported between 12h UT on November 16 to 12h UT on November 19 as the thick, irregular line (green = Far East and Australia; red = Europe; blue = the Americas), which is keyed to the left-hand y-axis. The thinner, red, daily-symmetrical curves describe the Leonid radiant's elevation above the horizon for each site, values keyed to the right-hand y-axis. In general, times when interference intervened, preventing accurate data collection, are shown by the count line dropping to zero.
As I have discussed before in earlier Leonid reports and other SPAMS results, the interpretation of radio data is not easy, but it is less difficult during very strong meteor activity such as a Leonid storm. Leonid activity was good enough in 2002 to produce at least one very clear radio peak for most of the observers reporting to us, either in the hours shortly before midnight UT on November 18-19 or during the UT day of November 19, as the accompanying radio graphs demonstrate. Even where neither storm maximum was radio-visible, such as in Japan and Australia, the build-up towards the best activity was very obvious. Europe was almost ideally located to catch both storm peaks under similar radiant elevation conditions, allowing a comparison of the relative appearances of both in the same observer's data in some cases. Over the Americas, the second storm peak was well-caught.
A consensus in most of the available radio results suggests Leonid rates began rising strongly from about 21h-22h UT onwards on November 18 over the Far East and Australia. The actual start of the rise was probably a few hours before this, possibly as early as 18h-19h UT. The Leonid radiant set around the time of the first storm maximum from most of these sites - except Taiwan, as noted earlier - so it was left to Europe to enjoy the best of this peak, as the radiant had yet to rise across the Americas. A possible minor pre-maximum peak, relatively rich in longer-duration echoes (normally taken to be produced by brighter meteors) seems to have happened around 03h-04h UT on November 19, perhaps centred around 03h30m-03h40m UT, though this is not certain. It would largely tally with the visually brighter magnitudes before 03h30m UT certainly. The first maximum fell in the one-hour interval between 04h-05h UT, unsurprisingly, and in the few datasets that reported 10-minute counts as well as the usual hourly intervals, the best activity occurred between 04h10m-04h20m UT. Given the collecting intervals and possible slight timing variations, this is very close to the visual results. The observers at the Ondrejov meteor radar in the Czech Republic announced their results on IMO-News late on November 19, indicating a peak time of 04h06m UT, conveniently very close to the SPAMS visual maximum timing too! The Ondrejov radar detects meteors as faint as magnitude +9, but their results indicated most Leonids were significantly brighter than this.
As activity declined after the first maximum, another possible minor peak was found around 05h-06h UT, most likely between 05h00m-05h10m UT. The Ondrejov radar also showed a small, short peak at about 05h06m UT, which gives some support for this feature. After this, radio activity trundled along in an elevated, but non-peak, state for several hours, until a potential longer-duration minor maximum cropped up in the 09h-10h UT interval, perhaps around 09h00m-09h10m UT. This does not show up clearly in the visual data, though only two observers were active during the critical 10-minute interval anyway.
The second maximum was clearly defined in the 10h-11h UT period, and there were possibly two phases of longer-duration echo counts, around 10h40m-10h50m and 11h10m-11h20m UT, but these did not appear especially strongly in all the available longer-duration data. There is little to support these in the visual findings, although the first did coincide with the main peak's timing, while after 11h UT, very few visual observers were able to remain active in North America, as dawn approached.
As noted above, European observers were almost ideally-sited to cover both maxima. On the whole, the second storm peak was recorded less strongly than the first in such data. There are a number of reasons why this might be so, dependent on things like transmitter-receiver geometries, the elevation and direction of the Leonid radiant at the time, although the number of results which show the same feature mean these reasons probably played a relatively minor role. It may be the second storm peak produced fewer meteors than the first, as our visual results suggest, but the picture appears more complex than this. The next two radio graphs here show hourly radio echo counts collected by two European observers throughout November 19, compared to the Leonid radiant elevation. David Entwistle in England provided information on the total numbers of meteor echoes he recorded, and the number of those echoes which were of longer duration, so give an indication of the likely proportions of brighter meteors. Ton Schoenmaker in the Netherlands provided corrected counts allowing for the amount of time lost each hour because his system was saturated by subsequent Leonid echoes blurring into one another. He also gave the percentage of such dead time per hour, and this is plotted on the same graph. System saturation like this seems to occur both when there are many meteors present and when higher rates of brighter meteors are happening (so the major shower maxima through the year often produce this kind of problem, even when there is no meteor storm).
Looking at the two graphs, the first Leonid maximum is plain enough, along with the second maximum at a lower level in the all-echo count lines. (The drop around 05h UT in David Entwistle's results was due to an uncertain cause; it does not recur so obviously in the other European data.) The swift rise to, and slower decline after, the first peak, and the relatively slow rise and sharper fall around the second maximum helpfully reflect the visual findings too. However, looking at David's longer duration counts, and Ton's lost-time percentages, the second maximum does not appear at all. This strongly suggests the second maximum was indeed lacking in brighter meteors, as the IMO visual data suggested and the SPAMS data hinted. Consequently, recomputing the SPAMS second peak value at 10h45m UT using the IMO r-value of 2.8 suggested for near that time, would bring this visual ZHR up to 3460 +/- 140, making the second peak now slightly higher than the first. Although somewhat conjectural, this value may well be closer to the true rate. More discussion of the two peaks is given below.
In sum, the radio data support the visual findings of two main peaks, similar in character and at coincident times for the two techniques, the first one of which was richer in brighter meteors. Several lesser items found in the radio analysis may have analogues in a close inspection of the visual results as well, though not necessarily all.
Photographic and video observations were submitted by only a few people. Drawing on data from four UK observers, Russell Cockman (Dumfries & Galloway), David Entwistle (Lancashire), Robin Leadbeater (Cumbria) and Cliff Meredith (Manchester), it has been possible to determine a surprisingly accurate Leonid radiant position for November 19 during and near the storm peak. A total of 52 Leonid trails were available, of which only 37 were suitable for the radiant derivation, and yielded a position centred at RA 10h12m +/- 10m, Dec +20 degrees +/- 3 degrees. This is an impressive result given the often poor sky conditions the imaging was carried out under, and compares very favourably with the theoretical Leonid radiant position for November 19 at RA 10h12m, Dec +21.3 degrees. Using 202 Leonid trails, part of his own video data collected on November 18-19 from southern Spain, Steve Evans computed a radiant position at RA 10h11.2m +/- 0.8m, Dec +21.7 degrees +/- 0.2 degrees, again an excellent result for the observing circumstances. Seven Leonid images are given below. More can be found on the following websites:
http://www.russellc.pwp.blueyonder.co.uk/Meteors/2002%20Leonids.htm (Russell Cockman)
http://www.d-entwistle.fsnet.co.uk/leonid.htm (David Entwistle)
http://www.leadbeaterhome.fsnet.co.uk/astro_image_21.htm (Robin Leadbeater)
|A superb Leonid fireball caught crossing through the Plough in Ursa Major, and perfectly in-shot (a great rarity as most meteor photographers will know only too well!), by David Entwistle at 02:56 UT on November 19, 2002, from Peel Park, Accrington, Lancashire. The magnitude was estimated at about -6. Conditions were bright moonlight and slight haze, as the image suggests. Taken using a Pentax MV with a 50mm lens, f/1.7, 30-second exposure, on Fuji Superia ISO 800 colour film. David managed to photograph two further images showing this meteor's train, which lasted for approximately one minute. On the first of these, another, but notably fainter, Leonid is seen crossing that image (not shown here).|
|Steve Evans had travelled from his home in England to Andalucia in Spain, joining teams from the Dutch Meteor Society and the Czech Republic's Ondrejov observatory, in the hopes of catching the Leonid storm under better skies than in Britain. In that, he was right, as his normal UK locations were overcast all night apparently. Unfortunately, even Spain managed to provide more moonlit cloud than he'd hoped. Steve had borrowed Andrew Elliott's video system "Elli" for the trip, which uses a 25mm second-generation MCP image intensifier and an f/2.8 16mm lens, giving a field of view of 90 degrees, and a stellar limiting magnitude under normal conditions of about +3.5.|
Taken at 05:17 UT on November 18 (the video-stamped date was incorrectly set on the first night), just about moonset, showing how good the sky in Andalucia can be. The Plough and the brighter stars of Ursa Minor are obvious in the centre and centre-left of the image, as is the bright Leonid.
This field of view at 03:51 UT on November 19 is the same as in Steve's Image 1, though now the effects of the moonlit thin cloud sheet blot out virtually all the stars. Luckily, not all the meteors met the same fate, as another splendid Leonid slips down into where Hercules should be!
|Robin Leadbeater in Cumbria was one of the UK's most successful video observers of the Leonid storm. He used a very sensitive Sony CCD video camera with a 70 x 50 degree field of view, and treated it a little like a very short exposure still camera, taking a series of 2-second exposures between 03:29-04:35 UT, recording a total of 43 easily-identified trails in 15.83 minutes. He was lucky in getting a 90% clear sky on November 18-19, and close to the storm peak, between 03:59-04:11 UT, he recorded a meteor about every 10-15 seconds! We show four of Robin's images here, each with a single Leonid on.|
Taken at 03:36 UT, Jupiter is the brightest "stellar" object to the right, with the "Sickle" or "Head" of Leo below it, and the "Bowl" of the Plough asterism in Ursa Major to the lower left. Castor and Pollux in Gemini and Procyon in Canis Minor are near the top right edge. The Leonid lies between Ursa Major's "Legs". The image has been slightly cropped and reprocessed to bring up the stars and the meteor trail better.
Similarly reprocessed to Image 1, and covering a similar area of sky, this shot at 04:01 UT near the storm's height, shows a Leonid darting across Lynx heading for Auriga. The brightest object is again Jupiter.
At 04:12 UT, a bright Leonid slips away by Jupiter. This is a cropped and reprocessed image just showing what the cloud has left uncovered of Leo's "Sickle" and Jupiter. The light-coloured area to the top right is thin cloud.
Now looking north, at 04:25 UT. Polaris is the brightest star visible near the middle, with the rest of Ursa Minor off to its right. Cassiopeia is on the left-centre edge, with Cepheus below it, just above the treeline. This shows the effects of moonlight on some of the thin cloud which drifted over during Robin's observations. The image has been slightly reprocessed to try to overcome the worst effects of this.
The video trail numbers recorded by Steve Evans and Robin Leadbeater showed closely similar patterns across the European storm maximum, and it has been possible to compare these combined raw video trail numbers with the visual, and some of the radio, results made at the same time. This is shown on the first of the two graphs here. The second graph of this pair shows a comparison between the visual and selected radio data for the North American storm peak (for which regrettably no video results were submitted to us). The abbreviated observer's names are: ENTDA = David Entwistle, REIIN = Ingo Reimann, and RENGI = Gilberto Klar Renner. These observers were chosen as they provided 10-min radio echo count data during the selected time intervals. Gilberto provided information on the amount of time per 10-min interval his system recorded longer duration echoes, which information has also been plotted on the second peak's graph.
The first maximum shows a simple pattern, with the video and visual peak times coinciding with one another, and in general showing similar trends throughout the 90 minutes of the graph. The radio peak timings all coincide with one another too, but seem to fall slightly later than the video-visual peak. This may be due to the fact that the radio data are given in 10-minute intervals, rather than the 5-minute ones for the other techniques, or may be a genuine aspect of the shower, but all the curves are quite similar to one another in shape and character, and to the video-visual activities.
In the second peak's graph, the patterns are not as straightforward. The visual and two of the radio count lines coincide as to the peak time, but the two South American longer-duration time peaks bracket the visual and all the radio maxima, without correlating to features shown by the other methods. Intriguingly, the European longer-duration echo line peaks just before the second South American one, coincident with one of the two European radio peak timings. Some of these problems may be due to the time interval lengths, although even more likely are problems with the radio observing technique overall, and the different systems detecting slightly different aspects of the shower peak to one another. There may remain a suggestion here that the second peak was rather more complex in nature than the first one, perhaps with overlapping sub-streams within the Leonid stream as a whole, each with varying meteoroid size-mass populations.
Following the pattern set in previous SPAMS Leonid reports, in addition to discussing the scientific results, we will now turn to how the observers reacted to what they saw - or sometimes missed seeing - on the maximum night, based on correspondence received in the weeks after the event. Before beginning a commentary on what actually happened however, it is worth noting that the British media had decided in advance that the event was going to be clouded-out across the country. For instance, The Independent for November 19, written the evening before, had a small item on how "the weather was expected to be cloudy enough to obscure the Leonids", while their leading article, "Damp squib", was more definite, with phrases like "Trust the British weather to spoil it", "And what happens? The usual cloud and rain, that's what", as if the event had already passed. Yet as the sketch map here illustrates, some observers barely 30km away from the newspaper's registered office in East London enjoyed the Leonids under partly clear skies, and many people away from the southern one-third of the mainland UK had an even better view!
This map draws on details sent to the Section, and on data kindly provided by the SPA Cloudwatch Project coordinator Terry Holmes, giving a view of how the UK fared on the critical Leonid storm night, with one symbol at times representing a number of people at the same or nearby sites. Terry himself, in the West Midlands, was unlucky: "I didn't see anything of the Leonids. After sunset...the sky was clearing and I prepared my equipment. But the weather forecast predicted cloud to increase, and this is what happened...By midnight there was the first fog of the autumn." However, just 70km north in Cheshire, skies were clear right through the storm maximum. Such was the fickle nature of the weather on November 18-19, as the remarks below help demonstrate.
Conditions were at their poorest in the post-midnight hours across parts of southern and central England. On the south-west coast, for Guy Ottewell in Dorset, "...the sky at 11 p.m. was almost covered with beautiful clouds like ice-floes, moonlit so that I could see the gaps between them and hope to see a few meteors...but from midnight onward the cloud had solidified." Further east in Sussex, Mike Feist, "...saw just one Leonid - at 2:27 a.m. - in a small hole in the clouds...That was it, as the clouds got worse and worse, and then nothing was visible by the magical 4 a.m." Pete Lawrence near Selsey Bill struggled with occasionally broken clouds, finally giving up at 4:40 a.m. after solid clouds since 3. He rose again at 6 a.m. for work: "Popping outside while I was getting ready for a 7 a.m. meeting, the area around Leo was covered by a large clear patch...I did 10 minutes of sight-seeing and saw 5 Leonids..." As Pete noted, a frustrating night, but at least he saw a few Leonids.
A little way north, in Surrey, skies were also trying, but rather less frustrating. Assistant SPAMS Director Shelagh Godwin at Godalming: "When I got up at 1:30 a.m. and saw cloud, I really thought `Am I going to be cheated yet again of the chance of a Leonid storm?' and went back to bed. However, encouraged by a bird singing an hour later, I did get up and go outside to find the clouds had melted away. For a blissful 45 minutes I watched Leonids coming at a rate of 2 or 3 every 10 minutes, and mostly bright. Then, at 3:20, just as the rates appeared to be increasing, thick clouds started rolling in from the south east. However they often had a few holes in them, and as the critical time of 3:50 approached, these holes got larger. Then I started seeing bright Leonids in the clouds and through the holes. It was obvious that the rates were much, much higher. Then amazingly, just after 4 a.m., the clouds parted like the Red Sea leaving a crystal clear sky full of meteors, and I had a wonderful 20 minutes or so. At 4:15 the clouds came back and stayed persistently for the next half hour. After they cleared at 4:45, there was still a good show of meteors, about 6 every 10 minutes. I finally went inside at 5:15 when the clouds came in again. But what a night. I was so pleased to have seen a Leonid storm at last."
Nearby, Paul Wolstenholme had been fogged-out on Epsom Downs, so moved to Box Hill, Surrey, observing between 3:20-4:50 a.m., spotting 190 Leonids. His feeling was that the shower, "reached maximum as predicted, at around 4 a.m., when I would estimate there were as many as 10 per minute...An excellent show." Slightly north in and near London, things were hopeless. Nigel Knighton, West London: "Well, I went out at 0, 2, 3, 4 hrs only to find cloud. Could not even see the Moon." Dave Campbell, Middlesex: "Broken clouds at 10 p.m. Misty and nearly overcast at midnight. And very misty with just a faint glimmer of Jupiter at 4 a.m. ...I did see one very faint flash that might have been a Leonid at about 4:20 a.m., but altogether a very disappointing night."
Further north-west, in Oxfordshire, former Meteor Section Director George Spalding had a difficult night too with fog lifting into low clouds from midnight till 3:40 a.m., when a breeze picked up and a few gaps appeared. "I was able to cover 4:00-4:30 and 4:45-5:15 a.m., though cloud cover was usually about 99% and rarely better than 95%, LM was at the very best, about 4, and more often I could see little except Jupiter." George spotted 18 Leonids, as he said, merely a tantalising glimpse of what lay above the near-overcast. Yet just a few kilometres away, Chris Holt had a better time, with a gap from Ursa Major to Leo and about as far south again of Leo from 4-4:50 a.m., sometimes with several Leonids a minute visible in the first half hour. "All meteors seen were bright - they needed to be...bright enough to be seen through tenuous cloud", or at times even while still in thicker patches.
Over in Essex, Si Clarke discovered thick fog and clouds at 3 a.m., but a second check at 3:30 a.m. revealed a clearer area to the east, still leaving 75-85% of the sky obscured: "From 3:45 to 4 a.m. I saw 8 Leonids, which is an 800% increase on all previous attempts to witness them...The clouds rolled back in at 4 a.m. and didn't break again, with the rain starting at 4:55 a.m. At which point I went back in - I know when I'm beaten."
As mentioned, central England had very poor conditions all night. Former SPA President Heather Couper with Nigel Henbest in Buckinghamshire, spotted a combined tally of just five Leonids beneath cloudy, foggy, and very damp skies between 3:30-4:30 a.m., while SPA Secretary Guy Fennimore in Nottinghamshire `enjoyed' only thick fog all night.
North-west of here were the best skies in England, over Cheshire, Manchester, Lancashire and Cumbria, extending west to include parts of North Wales. Meredic Hallett in Conwy had generally only a little thin, wispy cloud to contend with, and observed from 3:16-5:05 a.m. His best spell brought 54 Leonids in eight minutes from 4:04-4:12 a.m. "Some of the meteors came in bursts of 3 to 5 and were difficult to count they were so quick."
Paul Brierley, Cheshire: "Fortunately we did have clear skies for the peak at 4 a.m., when the sky lit up; it was a truly amazing spectacle...there were too many Leonids to record - I gave up trying at 3:51 and just enjoyed the view...One thing that struck me was how brief the peak was. It appeared to last for only a number of minutes." Paul Clark, Cheshire: "We saw 10-15 a minute around 4:00-4:10 a.m., including several groups of three through the `bowl' and `handle' of the Plough. Too many to count at 4:00. Once in a lifetime? I hope not." Former SPA Planetary Section Director Cliff Meredith, Manchester: "To my surprise the sky stayed clear, though milky...and it turned out to be one of those special astronomical occasions...which I will particularly remember." Long-standing observer Ian Rigney, Manchester: "As the night went on there was a slow but steady build up of meteors as the Leonid radiant climbed higher. At 3 a.m. it was as if someone had turned on a switch, as meteors started to come at one a minute and more...Just after 3:40 a.m. the Leonids stepped up another gear and meteors were coming so often that I could only keep a count; meteors were coming at 3-4 a second at times...the spell from 4:00-4:10 being particularly busy."
Paul Richardson, Lancashire: "Can't believe that just for once, the Manchester area seems to have been exceptionally clear for an astronomical event! I was very poorly prepared, having expected cloud cover from the west during the night...but the display was certainly the best I have ever seen". David Entwistle, Lancashire, observing 2-5:30 a.m.: "During the Leonids I concentrated on trying to get a decent photograph [succeeded! - see image above - AM], and didn't attempt to count rates...Generally, activity seemed to come in bursts, with several meteors in the space of a few seconds followed by a brief lull. However, during the peak, you'd seldom have to wait more than a few seconds for a meteor...Bright meteors seemed more common early on...Those arriving later, at the predicted peak, generally seemed fainter." Peter Duffy, Lancashire, having driven over from Yorkshire seeking better skies: "At first [about 1:30 a.m.] I was only seeing about one every ten minutes, but things suddenly picked up at 3:40, until at about 3:55 there were two breathtaking short bursts during which I lost count of the number of meteors visible. I really have never seen anything like it. At about 4:20, things were slowing down again, the clouds were thickening, and the cold and chattering teeth finally won!...A memorable night."
Robin Leadbeater, Cumbria: "...we were blessed with 9/10 clear skies (at least from 3:30 to 4:30 a.m. when I was looking skyward). I was concentrating on imaging, so did not keep any accurate records of visual activity, but...I spotted perhaps 2 or 3 per minute on average through the hour, with a couple of periods of higher activity around 4:00-4:15 where the rate was significantly higher, perhaps 7-10 a minute...mostly bright ones but almost all with short trails and no fireballs." Anita Evans, Cumbria: "I set my alarm for 3:55 a.m. and was out in the garden a few minutes after...I saw one quite bright one and wondered if that was the lot, then they started coming thick and fast. I suppose at about 4:10 it quietened down a bit...Then there was enough to keep me thinking `wow' until just after 4:30 when it started to get quiet again...half an hour on the sun-lounger (more action than it saw all summer)...rewarded by quite a display."
Westward in Northern Ireland, as has seemed often the case during the Leonids, skies were useless. Peter Phillips, Co Tyrone: "I'm afraid I was clouded out AGAIN! for the Leonids (5th year in a row, would you believe it?)" Meanwhile well east of Cumbria, Northumberland's skies did allow something of the Leonids to be seen at their best, both for myself, and a group elsewhere from the Northumberland Astronomical Society, as Adrian Janetta relates: "Against the odds, we had a fairly clear spell from about 3:35 to 4:25 a.m. Activity seemed to be most intense for a few minutes either side of 4:10 a.m...Sometimes there would be a flurry of meteors streaking across different parts of the sky at the same time. I wonder how many we weren't seeing?"
Southern to central Scotland was a splendid place to be for the Leonids, especially further west, but even in the east some better views were had. Mike Holmes, Edinburgh: "We went up Blackford Glen around 1 a.m.... There was sporadic misty cloud which seemed quite high...We saw a couple of dozen Leonids up to 3:45. After that there were two times when we saw 5 in a minute, and things took off at 4:00; we saw 26 between then and 4:10. We saw 19 in the next ten minutes and 5 in the ten minutes after that...Things petered out from 4:30 though we stayed until Castor and Pollux were lost in twilight around 7:00, with only an occasional meteor visible." Mike Dale of Royal Observatory Edinburgh: "On entering the garden at 3:10 a.m. my first impression was of a beautifully clear sky, but I soon realised that there was a thin haze over most of it. The Moon was yellowish and very murky-looking...However I quickly realised that there was a fairly steady stream of Leonids coming in. They were mainly faint with the odd one a little brighter. They were mainly single but with occasionally two or three in spurts...Overall I was quite delighted." Tom McEwan (with Nick Martin), Perth & Kinross: "It was raining here in N Ayrshire on the evening of the 19th...so, we drove through to Powmill, Perth and Kinross, and managed 90 minutes of observing, catching the peak. Conditions were not however ideal - there was a patchy veil of thin cloud and drifting cumulus...but we did see some striking activity."
Russell Cockman (with Walter Scott Jr.), Balmaclellan, Dumfries & Galloway: "There were many bright (mag 0 and brighter) events... Observation of the radiant around the time of the predicted maximum showed very brief bursts of activity with several meteors appearing simultaneously, then nothing. Overall impressions either side of the maximum were of meteor rates of several per minute. Even as dawn twilight intervened, meteors continued to be observed...The display was very entertaining despite the almost full Moon, patchy cloud cover and the cold." Roy Watson, East Dunbartonshire: "In spite of the negative weather predictions, I was able to observe the shower, cloud-free, from 3:22 until 6:25 a.m...it was a truly awesome and memorable display. The bulk of the Leonids were very bright, and there was much activity around 4:00." Colin Begg (with Craig Stobo, Sarah Watson and Chris Wilson), in Stirlingshire not far from Loch Lomond: "The peak for us clearly happened at 4:00-4:15 a.m. We were treated to a good display of meteors...Many - indeed a sizeable minority - left good trails and several easily outshone Jupiter."
European reports suggest conditions were patchy across the Continent too. Clearer skies were available for parts of Italy, southern France, Spain, Romania (especially for Transylvania; Moldavia was very poor, but Wallachia good in parts) and Morocco, but only overcast conditions were apparent in Belgium, the northern Netherlands, Slovenia and Croatia. Further afield, positive reports were received from large tracts of North America, especially in the eastern half of the USA, but the best view of all our regular overseas correspondents was Bob Lunsford's, who had been invited to observe with the NASA MAC Leonid team in two high-altitude aircraft. On the maximum night, the pair of aircraft flew across the Atlantic from Spain to Kansas in the USA, far above the clouds, so Bob was treated to a superb view of BOTH storm maxima - aside from the distraction of an aurora filling almost the entire sky at times over the USA! Comments from others of our overseas correspondents follow.
Ton Schoenmaker, Netherlands: "Visually, I saw almost nothing, 99% moonlit clouds most of the time." Hendrik Vandenbruaene, leader of the Belgian VVS meteor observing group, Belgium: "Leonids were terrible in Belgium... Most observers only saw a handful of meteors, if they were lucky...BUT, some other colleagues went to southern Spain and southern France, where they could make observations of the complete event." SPA Comet Section Director, Jonathan Shanklin, southern France: "...one of the first meteors was a bright, fragmenting Taurid, followed by a long-trailed Leonid. Rates were initially slow, with a meteor every few minutes...until half an hour before the predicted maximum...Rates then rapidly escalated, and at maximum, rose to about a dozen a minute, with some meteors appearing simultaneously...The three brightest meteors with long-lasting trains (about 30 seconds) occurred during the decline, and were bright enough to light up the ground. Even as dawn brightened the sky, rates were still around one a minute...a fantastique pluie des etoiles!" SPA Vice-President Robin Scagell (with his wife Sally and SPA Webmaster Paul Sutherland), southern France: "Around the peak, Sally counted 100 Leonids in just 10 minutes. There were few fireballs, but there were large numbers of fainter ones...As dawn began to break, the peak had passed, but meteors could still be seen falling at a rate of one or more a minute."
Mihaela Triglav, Slovenia: "...we were clouded and rained out...I went to sleep with the alarm set for 3 a.m., but it rained then, so I changed it to 4 a.m. - it rained again. At 5 it didn't rain any more, but there were low clouds everywhere, so I missed the maximum...I was a little bit disappointed not to see any Leonids, but I saw them three times in recent years, so I got my part of them already." Steve Evans, southern Spain: "I travelled to Spain with the DMS and Ondrejov observers again...as in 2000...The expedition was very enjoyable, and conditions on November 17-18 were superb...Leonid activity was low, but did seem to pick up a bit towards dawn. The maximum night started in promising fashion, with very clear skies, but thin cloud started to roll-in from the SW just after midnight, and was troublesome for the rest of the night...because of the clouds/Moon it was difficult to be completely objective about activity, but...the elevated activity was short-lived - starting around 3:30 a.m., peaking around 4:00 and tailing-off very rapidly after 4:30."
Rich Taibi, North Carolina, USA: "...forecasts suggested that travelling to North Carolina would help ensure clearer skies. The good news is that for the 2nd peak period, the sky was cloudless. The bad news was that tape problems distracted me, and I [accidentally] recorded over about two hours' data...[thankfully not from the most critical time! - AM] Like others who have commented on the 2nd peak, I saw mostly fainter meteors." Jay Brausch, North Dakota, USA: "I figured because the Moon was all full this year that my sky would finally be clear for the Leonids, and it was after 1:30 a.m...when I went out at 3:10, I was `lured' to my observing site by the activity. So, this strong shower...literally rose to the occasion...At best [in the hour after 3 a.m.] I was seeing 2-3 meteors per minute." All-in-all, a lot of very happy, lucky observers provided a generally positive view of the shower.
Lastly, on a sombre note, brief obituaries to two good friends who died in March 2003, Stanley Toyn of Exmouth, Devon, and Kath Hodges of Manchester. Neither were SPA members, nor even amateur astronomers, but both had provided notes and cuttings to the Section in the past, notably in recent years regarding the Leonids. Stanley had confirmed how poor his skies were for the 2002 Leonids, for instance. He was 79, and many years retired from his business in Manchester producing geological microscope slides and specimens. His interest in microscopy and his friendship with my father was how I came to know him. Although partly disabled by illness for a long time, he died unexpectedly of a heart attack on March 2. Kath worked in bioscience publishing, having a PhD in Fungal Genetics, and was just 39. Having successfully battled against breast cancer in the late 1990s, it was a dreadful blow when she was diagnosed with terminal liver cancer in November 2002. Given at least a year to live, she died unexpectedly early on March 29-30. Both are greatly missed by their families and many friends.
The following are a short selection of items published on the Leonids since our Annual Report 2001 was circulated. Brief notes are given only where the title was not felt to be descriptive enough.
Many and fulsome thanks go to all of our contributors in what was a wonderfully-observed and successful Leonid campaign in 2002. Good luck and clear skies for your next observing.
Alastair McBeath, SPA Meteor Section Director. 25th July 2003.