![[QUA-map]](qua.gif)
Welcome to the 2000 International Meteor Organization (IMO) Meteor Shower Calendar. The year promises many Moon-free major showers (except the Lyrids, Perseids, Orionids and Geminids), and the Leonids may produce high to storm rates in November. Of especial interest is the chance to see what the June Bootids produce in late June after their unexpected outburst in 1998. Do not forget that monitoring of meteor activity should ideally be carried on throughout the rest of the year too, however! We appreciate that this is not practical for many observers, and this Calendar was devised as a means of helping observers deal with reality by highlighting times when a particular effort may most usefully be employed. Although we include to-the-hour predictions for all the more active night-time and daytime shower maxima, based on the best available data, please note that in many cases, such maxima are not known more precisely than to the nearest 1° of solar longitude (even less accurately for the daytime radio showers, which have only recently begun to receive regular attention again). In addition, variations in individual showers from year to year mean past returns are at best only a guide as to when even major shower peaks can be expected, plus as some showers are known to show particle mass-sorting within their meteoroid streams, the radio, telescopic, visual/video and photographic meteor maxima may occur at different times from one another, and not necessarily just in these showers. The majority of data available are for visual shower maxima, so this must be borne in mind when employing other observing techniques.
The heart of the Calendar is the Working List of Visual Meteor Showers, thanks to regular updating from analyses using the IMO's Visual Meteor Database, the single most accurate listing available anywhere today for naked-eye meteor observing. Even this can never be a complete list of all meteor showers, since there are many showers which cannot be properly detected visually, and some which only photographic, radar, telescopic, or video observations can separate from the background sporadic meteors, present throughout the year.
The IMO's aims are to encourage, collect, analyze, and publish combined meteor data obtained from sites all over the globe in order to further our understanding of the meteor activity detectable from the Earth's surface. Results from only a few localized places can never provide such total comprehension, and it is thanks to the efforts of the many IMO observers worldwide since 1988 that we have been able to achieve as much as we have to date. This is not a matter for complacency, however, since it is solely by the continued support of many people across the whole world that our steps towards constructing a better and more complete picture of the near-Earth meteoroid flux can proceed. This means that all meteor workers, wherever they are and whatever methods they use to record meteors, should follow the standard IMO observing guidelines when compiling their information, and submit their data promptly to the appropriate Commission for analysis.
Visual and photographic techniques remain popular for nightly meteor coverage (weather permitting), although both suffer considerably from the presence of moonlight. Telescopic observations are much less popular, but they allow the fine detail of shower radiant structures to be derived, and they permit very low activity showers to be accurately detected. Video methods continue to be dynamically applied as in the last few years, and are starting to bear considerable fruit. These have the advantages, and disadvantages, of both photographic and telescopic observing, but are increasing in importance. Radio receivers can be utilized at all times, regardless of clouds, moonlight, or daylight, and provide the only way in which 24-hour meteor observing can be accomplished for most latitudes. Together, these methods cover virtually the entire range of meteoroid sizes, from the very largest fireball-producing events (using all-sky photographic patrols or visual observations) through to tiny dust grains producing extremely faint telescopic or radio meteors.
However and whenever you are able to observe, we wish you all a most successful year's work and very much look forward to receiving your data. Clear skies!
The year's first quarter brings several low activity showers, including the diffuse ecliptical stream complex of the Virginids, active from late January to mid-April. Both major showers, the northern-hemisphere Quadrantids and the southern-hemisphere alpha-Centaurids are excellently-placed with regard to the Moon this year. The minor delta-Cancrids are lost in the near-full Moon glare in January, but the weak delta-Leonids in late February and the gamma-Normids in mid-March fare better. Daylight radio peaks are theoretically due from the Capricornids/Sagittarids around 02h UT on February 2, and the chi-Capricornids on February 14, around 03h UT. Recent radio results suggest the Cap/Sgr peak may fall 2..3 days later than this however, while no significant enhancement in radio rates was found near the expected chi-Capricornid peak between 1994..1999. As both showers have radiants <10°..15° west of the Sun at maximum, they cannot be regarded as visual targets even from the southern hemisphere.
Active : January 1-5;
Maximum : January 4, 05h UT (lambda = 283.16°);
ZHR = 120 (can vary around 60-200);
Radiant : alpha = 230°, delta = +49°;
Radiant drift: see Table 6;
V = 41 km/s;
r = 2.1 at maximum, but variable;
TFC : alpha = 242°, delta = +75° and
alpha = 198°, delta = +40° (beta>40° N);
PFC : before 00h local time alpha = 150°, delta = +70°;
after 00h local time alpha = 180°, delta = +40° and
alpha = 240°, delta = +70° (beta>40° N).
Figure 1: Radiant position and drift of the Quadrantids
The year opens with a superb return of the Quadrantids for northern hemisphere observers, as the Moon is just two days before new on January 4. Since the shower's radiant is in northern Bootes, it is circumpolar for many northern locations, but it attains a useful elevation only after local midnight or so, and gets higher towards morning twilight. An interesting challenge is to try spotting the occasional long-pathed shower member from the southern hemisphere around dawn, but sensible Quadrantid watching cannot be carried out from such locations.
The maximum time given above is based on the best-observed return of the shower ever analyzed, from IMO 1992 data, confirmed by radio results in 1996, 1997 and 1999. A repeat of this time in 2000 would favor sites from Europe to the east coast of North America. The peak itself is normally short-lived, and can be easily missed in just a few hours of poor winter weather in the north, which may be why the ZHR level apparently fluctuates from year to year, but some genuine variability is probably present too. For instance, visual ZHRs in 1998 persisted for over two hours at their best. An added level of complexity comes from the fact that mass-sorting of particles across the meteoroid stream may make fainter objects (radio and telescopic meteors) reach maximum up to 14 hours before the brighter (visual and photographic) ones, so observers should be alert throughout the shower!
Past observations have suggested the radiant is very diffuse away from the maximum, contracting notably during the peak itself, although this may be a result of the very low activity normally seen away from the hours near maximum. Photographic and video observations from January 1..5 would be particularly welcomed by those investigating this topic, using the PFCs and TFCs given above, along with telescopic and visual plotting results.
Active : January 28-February 21; Maximum : February 8, 16h UT (lambda = 319.2°); ZHR = variable, usually around 6, but may reach 25+; Radiant : alpha = 210°, delta = -59°; Radiant drift: see Table 6; V = 56 km/s; r = 2.0. Figure 2: Radiant position and drift of the alpha-Centaurids![[ACE-map]](ace.gif)
The alpha-Centaurids are one of the main southern hemisphere high points in the opening months of the year, producing many very bright, even fireball-class, objects (meteors of at least magnitude -3). Their peak ZHR is normally around 5..10, but in 1974 and again in 1980, bursts of only a few hours' duration yielded activity closer to 20..30. As we have no means of telling when another such event might happen, photographic, video and visual observers are urged to be alert, especially this year, as the Moon is new just three days before their maximum. Thanks to their brilliance, even a normal alpha-Centaurid return is worth looking out for, and almost one-third leave fine persistent trains after them. The radiant is nearly circumpolar for much of the sub-equatorial inhabited Earth, and is at a useful elevation from late evening onwards.
Active : February 15 - March 10;
Maximum : February 25 (lambda = 336°);
ZHR = 2;
Radiant : alpha = 168°, delta = +16°;
Radiant drift: see Table 6;
V = 23 km/s;
r = 3.0;
TFC : alpha = 140°, delta = +37° and
alpha = 151°, delta = +22° (beta>10° N);
alpha = 140°, delta = -10° and
alpha = 160°, delta = 0° (beta<10° N).
Figure 3: Radiant position and drift of the delta-Leonids
![[DLE-map]](dle.gif)
This minor shower is probably part of the early Virginid activity. Rates are normally low, and its meteors are predominantly faint, so it is a prime candidate for telescopic investigation. Visual observers must make very accurate plots of the meteors to distinguish them from the nearby Virginids and the sporadics. Northern hemisphere sites have a distinct advantage for covering this stream, especially this year as the waning gibbous Moon will rise around or after midnight at the peak for sites north of 35° N latitude. Southern hemisphere watchers should not ignore the stream, as they are better-placed to note many of the other Virginid radiants, but with moonrise as early as 22h 30m at 35° S latitude on February 25, conditions are not ideal. At least the delta-Leonid radiant in mid-Leo is well on view for most of the night near the peak.
Active : February 25-March 22;
Maximum : March 13, (lambda = 353°);
ZHR = 8;
Radiant : alpha = 249°, delta= -51°;
Radiant drift: see Table 6;
V = 56 km/s;
r = 2.4;
TFC : alpha = 225°, delta = -26° and
alpha = 215°, delta = -45° (beta< 15° S).
Figure 4: Radiant position and drift of the gamma-Normids
![[GNO-map]](gno.gif)
gamma-Normid meteors are similar to the sporadics in appearance, and for most of their activity period, their ZHR is virtually undetectable above this background rate. The peak itself is normally quite sharp, with ZHRs of 3+ noted for only a day or two to either side of the maximum. Activity may vary somewhat at times, with occasional broader, or less obvious, maxima having been reported in the past. Post-midnight watching yields best results, when the radiant is rising to a reasonable elevation from southern hemisphere sites. First quarter Moon on March 13 is thus excellent news, as it will set before midnight. All forms of observation can be carried out for the shower, though most northern observers will see nothing from it.
April Piscids -- April 20, 02h UT; delta-Piscids -- April 24, 01h UT; epsilon-Arietids -- May 9, 00h UT; May Arietids -- May 16, 01h UT; o-Cetids -- May 20, 00h UT; Arietids -- June 7, 03h UT; zeta-Perseids -- June 9, 03h UT; beta-Taurids -- June 28, 02h UT.
Some signs of most of these peaks were found in data from 1994-1998, except the April Piscids and May Arietids. The ecliptical complexes continue with some late Virginids and the best from the minor Sagittarids in May..June. Visual observers hoping to see any possible June Lyrid peak this year on June 15 will be severely hampered by full Moon.
Active : April 19-May 28;
Maximum : May 5, 17h UT (lambda = 45.5°);
ZHR = 60 (occasionally variable);
Radiant : alpha = 338°, delta = -01°;
Radiant drift: see Table 6;
V = 66 km/s;
r = 2.7;
TFC : alpha = 319°, delta = +10° and
alpha = 321°, delta = -23° (beta<20° S).
Figure 5: Radiant position and drift of the eta-Aquarids
![[ETA-map]](eta.gif)
This is a fine, rich stream associated with Comet 1P/Halley, like the Orionids of October, but it is visible for only a few hours before dawn essentially from tropical and southern hemisphere sites. Some useful results have come even from sites around 40° N latitude in recent years however, and occasional meteors have been reported from further north, but the shower would benefit from increased observer activity generally. The fast and often bright meteors make the wait for radiant-rise worthwhile, and many events leave glowing persistent trains after them. While the radiant is still very low, eta-Aquarid meteors tend to have very long paths too, which can mean observers underestimate the apparent speeds of the meteors, so extra care is needed when making such angular speed estimates.
A relatively broad maximum, sometimes with a variable number of submaxima, usually occurs in early May. ZHRs are generally above 30 for almost a week centred on the main peak, based on IMO observations between 1988..1997. With new Moon on May 4, the shower is perfectly-placed for watchers in 2000. All forms of observing can be used to study the eta-Aquarids, with radio work allowing activity to be followed even from mid-northern latitude sites throughout the daylight morning hours. The radiant culminates at about 08h local time.
Active : June 26-July 2;
Maximum : June 27, 01h UT (lambda = 95.7°);
ZHR = variable, 0..100+
Radiant : alpha = 224°, delta = +48°;
Radiant drift: see Table 6;
V = 18 km/s;
r = 2.2;
TFC : alpha = 156°, delta = +64° and
alpha = 289°, delta = +67° (beta=25..60° N).
Figure 6: Radiant position and drift of the June Bootids
![[JBO-map]](jbo.gif)
Following the wholly unexpected strong return of this shower in 1998, we are delighted to reintroduce the June Bootids to the Working List of visual meteor showers this year, and to encourage all observers to routinely monitor the expected activity period in case of future outbursts. Prior to 1998, only four definite returns of the shower had been detected, in 1916, 1921 and 1927. With no significant visual reports between 1928..1997, we were justified in assuming the stream no longer encountered the Earth, and accordingly removed the shower from the Working List in 1996. The dynamics of the stream are not well understood. The shower's parent comet 7P/Pons-Winnecke was last at perihelion in January 1996, and its orbit currently lies around 0.24 astronomical units outside the Earth's orbit at its closest approach, so we have no way at present to predict likely future activity. In 1998, high Bootid rates (ZHRs 50..100+) were visible for more than half a day, beginning shortly before the time indicated above, again quite contrary to the short-lived nature of other known shower outbursts. The radiant is at a useful elevation for most of the short summer night in the northern hemisphere (only), and the waning crescent Moon, just four days from new, will present no real problems.
Minor shower activity continues apace from near-ecliptic sources throughout this quarter, first from the Sagittarids, then the Aquarid and Capricornid showers, and finally the Piscids (whose most likely peak on September 19 will suffer from the bright waning Moon) into September. The two strongest sources, the Southern delta-Aquarids and the alpha-Capricornids, are free from moonlight this year, along with the less-active Piscis Austrinids, Southern iota-Aquarids and Northern delta-Aquarids. Something of the Pegasids should still be seen in early July as well, but the July Phoenicids (peak July 13), Perseids (maxima expected near 05h and 10h UT on August 12; if the tertiary peak - seen so far only in 1997 - repeats in 2000, that should fall around 19h UT on August 12), kappa-Cygnids (maximum August 17) and Northern iota-Aquarids (peak August 19) all lose their best rates to bright moonlight. The alpha-Aurigids are much more favourable, and even the delta-Aurigids in early September are not too unfavourable. For daylight radio observers, the interest of May..June has waned, but there remain the visually-inaccessible gamma-Leonids (peak circa August 25, 03h UT, though not found in recent radio results), and a tricky visual shower, the Sextantids (maximum expected September 27, 03h UT, but possibly occurring a day earlier). The latter prediction is perfectly timed for new Moon, though the radiant rises less than an hour before dawn in either hemisphere.
Active : July 7-13;
Maximum : July 9 (lambda = 107.5°);
ZHR = 3;
Radiant : alpha = 340°, delta = +15°;
Radiant drift: see Table 6;
V = 70 km/s;
r = 3.0;
TFC : alpha = 320°, delta = +10° and
alpha = 332°, delta = +33° (beta>40° N);
alpha = 357°, delta = +02° (beta<40° N).
Monitoring this short-lived minor shower is never easy, as a few cloudy nights mean its loss for visual observers. The shower is best-seen in the second half of the night, good news as the waxing gibbous Moon will set soon after midnight for the more favorable northern hemisphere sites, to 00h 30m at 35° S latitude. The maximum ZHR is generally low, and swift, faint meteors can be expected. Telescopic observing would be especially useful.
Active : July 15-August 10;
Maximum : July 27 (lambda = 125°);
ZHR = 5;
Radiant : alpha = 341°, delta = -30°;
Radiant drift: see Table 6;
V = 35 km/s;
r = 3.2;
TFC : alpha = 255° to 0°, delta = 0° to +15°,
choose pairs separated by about 30° in alpha (beta<30° N).
Active : July 12-August 19; Maximum: July 27, 18h UT (lambda = 125°);
ZHR = 20;
Radiant : alpha = 339°, delta = -16°;
Radiant drift: see Table 6;
V : 41 km/s;
r = 3.2;
TFC : alpha = 255° to 0°, delta = 0° to +15°,
choose pairs separated by about 30° in alpha (beta<40° N).
Active : July 3-August 15;
Maximum : July 29 (lambda = 127°);
ZHR = 4;
Radiant : alpha = 307°, delta = -10°;
Radiant drift: see Table 6;
V = 23 km/s;
r = 2.5;
TFC : alpha = 255° to 0°, delta = 0° to +15°,
choose pairs separated by about 30° in alpha (beta<40° N).
PFC : alpha = 300°, delta = +10° (beta>45° N),
alpha = 320°, delta = -05° (beta = 0° to 45° N),
alpha = 300°, delta = -25° (beta<0° S.)
Active : July 25-August 15;
Maximum : August 4 (lambda = 132°);
ZHR = 2;
Radiant : alpha = 334°, delta = -15°;
Radiant drift: see Table 6;
V = 34 km/s;
r = 2.9;
TFC : alpha = 255° to 0°, delta = 0° to +15°,
choose pairs separated by about 30° in alpha (beta<30° N).
Active : July 15-August 25;
Maximum : August 8 (lambda = 136°);
ZHR = 4;
Radiant : alpha = 335° , delta = -05°;
Radiant drift: see Table 6;
V = 42 km/s;
r = 3.4;
TFC : alpha = 255° to 0°, alpha = 0° to +15°,
choose pairs separated by about 30° in alpha (beta<30° N).
Figure 7: Radiant position and drift of Aquarid radiant complex
![[AQR-map]](aqr.gif)
The Aquarids and Piscis Austrinids are all streams rich in faint meteors, making them well-suited to telescopic work, although enough brighter members exist to make visual and photographic observations worth the effort too, primarily from more southerly sites. Radio work can be used to pick up the Southern delta-Aquarids especially, as the most active of these showers. The alpha-Capricornids are noted for their bright - sometimes fireball-class - events, which, combined with their low apparent velocity, can make some of these objects among the most impressive and attractive an observer could wish for. A minor enhancement of alpha-Capricornid ZHRs to about 10 was noted in 1995 by European IMO observers, although the Southern delta-Aquarids were the only one of these streams previously suspected of occasional variability.
Such a concentration of radiants in a small area of sky means that familiarity with where all the radiants are is essential for accurate shower association for all observing nights. Visual watchers in particular should plot all potential stream members seen in this region of sky rather than trying to make shower associations in the field. The only exception is when the Southern delta-Aquarids are near their peak, as from southern hemisphere sites in particular, rates may become too high for accurate plotting.
In 2000 the Piscis Austrinid, Southern delta-Aquarid, alpha-Capricornid and Northern iota-Aquarid maxima benefit from new Moon on July 31, while the Northern delta-Aquarid peak has only a few problems from the waxing gibbous Moon, which will set between 23h and 01h 30m local time in either hemisphere. All these radiants are above the horizon for much of the night.
Active : August 25-September 5;
Maximum : August 31, 18hUT (lambda = 158.6°);
ZHR = 10;
Radiant : alpha = 084°, delta = +42 ;
Radiant drift: see Table 6;
V = 66 km/s;
r = 2.5.
TFC : alpha = 052°, delta = +60°,
alpha = 043°, delta = +39° and
alpha = 023°, delta = +41° (beta>10° S).
Active : September 5 - October 10;
Maximum : September 8 (lambda = 166°);
ZHR = 6;
Radiant : alpha = 060° , delta = +47°;
Radiant drift: see Table 6;
V = 64 km/s;
r = 3.0.
TFC : alpha = 052°, delta = +60°,
alpha = 043°, delta = +39° and
alpha = 023°, delta = +41° (beta>10° S).
Figure 8: Radiant position and drift of the alpha- and delta-Aurigids
![[AUR/DAU-map]](aur.gif)
These are both essentially northern hemisphere showers, badly in need of more observations. They are part of a series of poorly-observed showers with radiants in Aries, Perseus, Cassiopeia and Auriga, active from late August into October. British and Italian observers independently reported a possible new radiant in Aries during late August 1997 for example. Of the known showers, the alpha-Aurigids are the more active, with short unexpected bursts having given EZHRs of about 30..40 in 1935, 1986 and 1994, although they have not been monitored regularly until very recently, so other outbursts may have been missed. The delta-Aurigids typically produce low rates of generally faint meteors, and have yet to be well-seen in more than an occasional year. Both radiants reach a useful elevation only after 23h..00h local time, meaning lunar circumstances are near perfect for the alpha-Aurigid peak in 2000, with new Moon on August 29, while the delta-Aurigids enjoy dark skies after moonset (between 00h..01h local time north of 20° N latitude). Telescopic data to examine all the radiants in this region of sky - and possibly observe the telescopic beta-Cassiopeids simultaneously - would be especially valuable, but photographs, video records and visual plotting would be welcomed too.
Ecliptical minor shower activity reaches what might be regarded as a peak in early to mid November, with the Taurid streams in action. Unfortunately, both Northern and Southern Taurid maxima suffer from bright moonlight this year, but the interesting late October to early November period which sometimes produces more Taurid fireballs is excellently Moon-free. Taurid activity in late October 1998 reached levels comparable to the usual maximum rates, and checking what happens this year would be valuable, though nothing unusual has been predicted. Before then is a partly moonless Draconid epoch, together with badly Moon-affected epsilon-Geminid and Orionid maxima, all in October. The main Orionid peak is likely around 02h..03h UT on October 21 for radio observers. Some predictions suggest a Leonid storm may occur in November, but moonlight will be a problem. However, the alpha-Monocerotid peak is nearly Moon-free, together with the chi-Orionids in December. Shower maxima lost to moonlight in December include those of the Phoenicids (December 6 around 02h UT), early December's best from the Puppid-Velids, the Monocerotids (December 8), sigma-Hydrids (December 11), Geminids (December 13, 17h UT to December 14, 02h UT) and Coma Berenicids (December 19). The Ursids at least survive this lunar-light onslaught.
Active : October 6-10;
Maximum : October 8, 01h 30m UT, (lambda = 195.075°), or
October 8, 09h UT (lambda = 195.4°);
ZHR = periodic, up to storm levels;
Radiant : alpha = 262°, delta = +54°;
Radiant drift: negligible;
V = 20 km/s;
r = 2.6;
TFC : alpha = 290°, delta = +65° and
alpha = 288°, delta = +39° (beta>30° N).
Figure 9: Radiant position and drift of the Draconids
![[GIA-map]](gia.gif)
Unfortunately for potential Draconid observers, although this periodic shower has produced spectacular, brief, meteor storms twice already this century, in 1933 and 1946, and lower rates in several other years (ZHRs about 20..500+), so far, detectable activity has only been seen in years when the stream's parent comet, 21P/Giacobini-Zinner, has returned to perihelion. It did this last in 1998 November, and in 1998 October, a short-lived Draconid outburst yielding ZHRs of about 700 was seen from Far Eastern sites, as well as being recorded by radio. This occurred at lambda=195.075°, but a later time towards lambda=195.4° may be more generally applicable, based on the Earth's closest approach to the comet orbit's node. Activity in 2000 is unlikely, and conditions are far from ideal with a waxing gibbous Moon, but checking is important. The radiant is circumpolar from many northern hemisphere locations, but is higher in the pre-midnight and near-dawn hours on October 8..10. With moonset only after local midnight, a repeat of the 1998 peak time would favour sites in central to eastern North America, while the later time would be better for European to West Asian observers. Note that Draconid meteors are exceptionally slow-moving, a characteristic which helps separate genuine shower meteors from sporadics accidentally lining up with the radiant.
Active : November 14-21;
Maximum : November 17, 08h UT (lambda = 235.27°),
ZHR = 100+ (about 150? in 1997, about 340 in 1998), but may reach storm levels in 2000;
Radiant : alpha = 153°, delta = +22°;
Radiant drift: see Table 6;
V = 71 km/s;
r = 2.9;
TFC : alpha = 140°, delta = +35° and
alpha = 129°, delta = +6° (beta>35° N); or
alpha = 156°, delta = -3° and
alpha = 129°, delta = +6° (beta<35° N);
PFC : before 00h local time alpha = 120°, delta = +40° (beta>40° N);
before 04h local time alpha = 120°, delta = +20° (beta>0° N);
and after 04h local time alpha = 160°, delta = 0° (beta>0° N);
before 04h local time alpha = 120°, delta = +10° (beta<0° N)
and after 04h local time alpha = 160°, delta = -10° (beta<0° N).
Figure 10: Radiant position and drift of the Leonids
![[LEO-map]](leo.gif)
The Leonids' parent comet, 55P/Tempel-Tuttle, reached perihelion last in 1998 February, but recent stream evolution studies suggest high to storm-level Leonid activity may still occur in 2000 or even until 2002. There are, of course, no guarantees that this will happen, but all observers must realise that even discovering the absence of any unusual Leonid activity would still be very valuable information - albeit not all that interesting to witness! Young material from the most recent, i.e. the 1965 and 1932 perihelion passages of the comet, is likely to cause enhanced activity near closest approach to the comet's node on November 17, 08h UT (lambda = 235.27°), as also indicated by the stream model developed by Peter Brown, but the model finds an older trail from 1733 suggesting a peak as late as November 18, 08h UT. This finding is supported by the studies of David Asher and Robert McNaught yielding November 18, 03h 45m for the 1733 trail and another possible peak at 07h 50m for the 1866 trail. A repeat of the spectacular and extended fireball outburst seen in 1998 is regrettably unlikely this year.
The radiant rises only around local midnight (or indeed afterwards south of the equator), so the waning gibbous Moon will be a considerable nuisance for all observers. The two about 08h UT peak timings would favor locations across North America, while the 03h 45m possible peak would be best-seen from Europe and North Africa. Even minor variations from these timings would mean places east or west of these zones may see something of the shower's best too. Look out for further updates in the IMO's journal WGN after the 1999 return. All observing methods should be utilised, especially photography and video if a storm manifests.
Active : November 15-25;
Maximum : November 21, 08h UT (lambda = 239.32°),
ZHR = variable, usually around 5 but may produce outbursts to around 400+;
Radiant : alpha = 117°, delta = +1°;
Radiant drift: see Table 6;
V = 65 km/s;
r = 2.4;
TFC : alpha = 115°, delta = +23° and
alpha = 129°, delta = +20° (beta>20° N); or
alpha = 110°, delta = -27° and
alpha = 98°, delta = +6° (beta<20° N);
Figure 11: Radiant position and drift of the alpha-Monocerotids
![[AMO-map]](amo.gif)
Another late-year shower capable of producing surprises, the alpha-Monocerotids gave their most recent brief outburst in 1995 (the top EZHR, about 420, lasted just five minutes; the entire outburst 30 minutes). Many observers across Europe witnessed it, and we have been able to completely update the known shower parameters as a result. Whether this indicates the proposed ten-year periodicity in such returns is real or not, only the future will tell, however, so all observers should continue to monitor this source closely. We are currently at the mid-point of any decade-long cycle. The waning crescent Moon on November 21 makes this a good year for such scrutiny, with the radiant well on view in both hemispheres after about 23h local time or so. The expected peak time falls especially well for North America.
Active : November 26-December 15;
Maximum : December 1, (lambda = 250),
ZHR = 3;
Radiant : alpha = 082°, delta = +23°;
Radiant drift: see Table 6;
V = 28 km/s;
r = 3.0;
TFC : alpha = 083°, delta = +09° and
alpha = 080°, delta = +24° (beta>30° S).
Figure 12: Radiant position and drift of the chi-Orionids
![[XOR-map]](xor.gif)
A weak visual stream, but moderately active telescopically. Some brighter meteors have been photographed too. The shower has at least a double radiant, but the southern branch has been rarely detected. The chi-Orionids may be a continuation of the ecliptic complex after the Taurids cease to be active. The radiant used here is a combined one, suitable for visual work, although telescopic or video observations should be better-able to determine the exact radiant structure. The waxing crescent Moon should give few problems, as the radiant is well on display in both hemispheres throughout the night.
Active : December 17-26;
Maximum : December 22, 06h UT (lambda = 270.7°);
ZHR = 10 (occasionally variable up to 50);
Radiant : alpha = 217°, delta = +76°;
Radiant drift: see Table 6;
V = 33 km/s;
r = 3.0;
TFC : alpha = 348°, delta = +75° and
alpha = 131°, delta = +66° (beta>40° N);
alpha = 63°, delta = +84° and
alpha = 156°, delta = +64° (beta 30° to 40° N);
Figure 13: Radiant position of the Ursids
![[URS-map]](urs.gif)
A very poorly-observed northern hemisphere shower, but one which has produced at least two major outbursts in the past half-century or so, in 1945 and 1986. Several other rate enhancements, recently in 1988 and 1994, have been reported too. Other similar events could easily have been missed due to poor weather or too few observers active. All forms of observation can be used for the shower, since many of its meteors are faint, but with so little work carried out on the stream, it is impossible to be precise in making statements about it. The radio maximum in 1996 occurred around lambda=270.8°, for instance, which might suggest a slightly later maximum time in 1998 of December 22, 08h 30m UT. The Ursid radiant is circumpolar from most northern sites (thus fails to rise for most southern ones), though it culminates after daybreak, and is highest in the sky later in the night. The nearly-new Moon will give dark skies for observations almost all night on December 22.
If you are not observing during a major-shower maximum, it is much more essential to associate meteors with their radiants correctly, since the total numbers will be small. Meteor plotting allows the a shower association by more objective criteria than the prolongation of paths under the sky. As you plotted the meteors on gnomonic maps, you can trace the radiant by straight lines. If the radiant lies on another chart, you should find common stars on an adjacent chart to extend the backward prolongation there.
How large should the radiant be assumed for shower association? The physical radiant size is very small; visual plotting errors cause many true shower meteors to pass the radiant outside this area. We have to asume a larger radiant. The opposite behavior is caused by sporadic meteors - more and more sporadics line up accidentally upon enlarging the radiant. Hence, we have to apply an optimum radiant diameter compensating the loss due to plotting errors, and the sporadic meteor pollution. Table 1 gives the optimum diameter as a function of the distance of the meteor from the radiant.
D optimum
diameter
15° 14°
30° 17°
50° 20°
70° 23°
The direction of the path is not the only criterion for shower association. The angular velocity of the meteor should match the expected speed of the shower meteors according to the geocentric velocity of the meteoroids. Angular velocity estimates should be made in degrees per second (°/s). In your imagination you make the meteors move for one second. The path length of this imaginary meteor is the angular velocity in °/s. Note that typical speeds are in the range 3°/s to 25°/s. Typical errors of such estimates are given in Table 2.
angular velocity °/s 5 10 15 20 30 permitted error °/s 3 5 6 7 8
In you found a meteor which hits the radiant within the above diameter, check its angular velocity. Table Table 3 gives the angular speeds for a few geocentric velocities, which can be looked up in Table 5 for each shower.
V=25 km/s V=40km/s V=60km/s
D 10° 20° 40° 60° 90° 10° 20° 40° 60° 90° 10° 20° 40° 60° 90°
10° 0.4 0.9 1.6 2.2 2.5 0.7 1.4 2.6 3.5 4.0 0.9 1.8 3.7 4.6 5.3
20° 0.9 1.7 3.2 4.3 4.9 1.4 2.7 5.0 6.8 7.9 1.8 3.5 6.7 9.0 10
40° 1.6 3.2 5.9 8.0 9.3 2.6 5.0 9.5 13 15 3.7 6.7 13 17 20
60° 2.2 4.3 8.0 11 13 3.5 6.8 13 17 20 4.6 9.0 17 23 26
90° 2.5 4.9 9.3 13 14 4.0 7.9 15 20 23 5.3 10 20 26 30
alpha, delta: Coordinates for a shower's radiant position, usually at maximum; alpha is right ascension, delta is declination. Radiants drift across the sky each day due to the Earth's own orbital motion around the Sun, and this must be allowed for using the details in Table 6 for nights away from the listed shower maxima.
r: Population index, a term computed from each shower's meteor magnitude distribution. r = 2.0..2.5 is brighter than average, while r above 3.0 is fainter than average.
lambda: Solar longitude, a precise measure of the Earth's position on its orbit which is not dependent on the vagaries of the calendar. All lambda are given for the equinox J2000.0.
V: Atmospheric or apparent meteoric velocity given in km/s. Velocities range from about 11 km/s (very slow) to 72 km/s (very fast). 40 km/s is roughly medium speed.
ZHR: Zenithal Hourly Rate, a calculated maximum number of meteors an ideal observer would see in perfectly clear skies with the shower radiant overhead. This figure is given in terms of meteors per hour. Where meteor activity persisted at a high level for less than an hour, or where observing circumstances were very poor, an estimated ZHR (EZHR) is used, which is less accurate than the normal ZHR.
TFC and PFC: suggested telescopic and photographic field centers respectively. beta is the observer's latitude ("<" means "south of" and ">" means "north of"). Pairs of telescopic fields must be observed, alternating about every half hour, so that the positions of radiants can be defined. The exact choice of TFC or PFC depends on the observer's location and the for video camera fields as well.
New First Full Last Moon Quarter Moon Quarter January 06 January 14 January 21 January 28 February 05 February 12 February 19 February 27 March 06 March 13 March 20 March 28 April 04 April 11 April 18 April 26 May 04 May 10 May 18 May 26 June 02 June 09 June 16 June 25 July 01 July 08 July 16 July 24 July 31 August 07 August 15 August 22 August 29 September 05 September 13 September 21 September 27 October 05 October 13 October 20 October 27 November 04 November 11 November 18 November 25 December 04 December 11 December 18 December 25
Shower Activity Maximum Radiant V r ZHR IMO
Period Date lambda alpha delta Code
° ° ° km/s
Quadrantids Jan 01-Jan 05 Jan 04 283.16 230 +49 41 2.1 120 QUA
delta-Cancrids Jan 01-Jan 24 Jan 17 297 130 +20 28 3.0 4 DCA
alpha-Centaurids Jan 28-Feb 21 Feb 08 319.2 210 -59 56 2.0 6 ACE
delta-Leonids Feb 15-Mar 10 Feb 25 336 168 +16 23 3.0 2 DLE
gamma-Normids Feb 25-Mar 22 Mar 13 353 249 -51 56 2.4 8 GNO
Virginids Jan 25-Apr 15 (Mar 24)(004) 195 -04 30 3.0 5 VIR
Lyrids Apr 16-Apr 25 Apr 21 032.1 271 +34 49 2.9 15 LYR
pi-Puppids Apr 15-Apr 28 Apr 23 033.5 110 -45 18 2.0 var. PPU
eta-Aquarids Apr 19-May 28 May 05 045.5 338 -01 66 2.7 60 ETA}
Sagittarids Apr 15-Jul 15 (May 19)(059) 247 -22 30 2.5 5 SAG
June Bootids Jun 26-Jul 02 Jun 27 095.7 224 +48 18 2.2 var. JBO
Pegasids Jul 07-Jul 13 Jul 09 107.5 340 +15 70 3.0 3 JPE
July Phoenicids Jul 10-Jul 16 Jul 13 111 032 -48 47 3.0 var. PHE
Piscis Austrinids Jul 15-Aug 10 Jul 27 125 341 -30 35 3.2 5 PAU
Southern delta-Aquarids Jul 12-Aug 19 Jul 27 125 339 -16 41 3.2 20 SDA
alpha-Capricornids Jul 03-Aug 15 Jul 29 127 307 -10 25 2.5 4 CAP
Southern iota-Aquarids Jul 25-Aug 15 Aug 04 132 334 -15 34 2.9 2 SIA
Northern delta-Aquarids Jul 15-Aug 25 Aug 08 136 335 -05 42 3.4 4 NDA
Perseids Jul 17-Aug 24 Aug 12 139.8 046 +58 59 2.6 140 PER
kappa-Cygnids Aug 03-Aug 25 Aug 17 145 286 +59 25 3.0 3 KCG
Northern iota-Aquarids Aug 11-Aug 31 Aug 19 147 327 -06 31 3.2 3 NIA
alpha-Aurigids Aug 25-Sep 05 Aug 31 158.6 084 +42 66 2.5 10 AUR
delta-Aurigids Sep 05-Oct 10 Sep 08 166 060 +47 64 3.0 6 DAU
Piscids Sep 01-Sep 30 Sep 19 177 005 -01 26 3.0 3 SPI
Draconids Oct 06-Oct 10 Oct 08 195.4 262 +54 20 2.6 var. GIA
epsilon-Geminids Oct 14-Oct 27 Oct 18 205 102 +27 70 3.0 2 EGE
Orionids Oct 02-Nov 07 Oct 21 208 095 +16 66 2.9 20 ORI
Southern Taurids Oct 01-Nov 25 Nov 05 223 052 +13 27 2.3 5 STA
Northern Taurids Oct 01-Nov 25 Nov 12 230 058 +22 29 2.3 5 NTA
Leonids Nov 14-Nov 21 Nov 17 235.27 153 +22 71 2.5 100+ LEO
alpha-Monocerotids Nov 15-Nov 25 Nov 21 239.32 117 +01 65 2.4 var. AMO
chi-Orionids Nov 26-Dec 15 Dec 01 250 082 +23 28 3.0 3 XOR
Phoenicids Nov 28-Dec 09 Dec 06 254.25 018 -53 18 2.8 var. PHO
Puppid-Velids Dec 01-Dec 15 (Dec 07)(255) 123 -45 40 2.9 10 PUP
Monocerotids (Dec) Nov 27-Dec 17 Dec 09 257 100 +08 42 3.0 3 MON
sigma-Hydrids Dec 03-Dec 15 Dec 11 260 127 +02 58 3.0 2 HYD
Geminids Dec 07-Dec 17 Dec 13 262.0 112 +33 35 2.6 120 GEM
Coma Berenicids Dec 12-Jan 23 Dec 19 268 175 +25 65 3.0 5 COM
Ursids Dec 17-Dec 26 Dec 22 270.7 217 +76 33 3.0 10 URS
Showers may have other or additional peak times; see text.
COM DCA QUA
Jan 0 186 +20 112 +22 228 +50
Jan 5 190 +18 116 +22 231 +49
Jan 10 194 +17 121 +21
Jan 20 202 +13 130 +19 ACE VIR
Jan 30 200 -57 157 +16 DLE
Feb 10 214 -60 165 +10 155 +20 GNO
Feb 20 225 -63 172 +6 164 +18 225 -53
Feb 28 178 +3 171 +15 234 -52
Mar 10 186 0 180 +12 245 -51
Mar 20 192 -3 256 -50
Mar 30 198 -5
Apr 10 SAG LYR PPU 203 -7
Apr 15 224 -17 263 +34 106 -44 ETA 205 -8
Apr 20 227 -18 269 +34 109 -45 323 -7
Apr 25 230 -19 274 +34 111 -45 328 -5
Apr 30 233 -19 332 -4
May 5 236 -20 337 -2
May 10 240 -21 341 0
May 20 247 -22 350 +5
May 30 256 -23
Jun 10 265 -23
Jun 15 270 -23
Jun 20 275 -23 JBO
Jun 25 280 -23 223 +48
Jun 30 284 -23 225 +47 CAP JPE
Jul 5 289 -22 285 -16 SDA 338 +14
Jul 10 293 -22 PHE 289 -15 325 -19 NDA 341 +15 PER PAU
Jul 15 298 -21 032 -48 294 -14 329 -19 316 -10 012 +51 330 -34
Jul 20 299 -12 333 -18 319 -9 SIA 018 +52 334 -33
Jul 25 303 -11 337 -17 323 -9 322 -17 023 +54 338 -31
Jul 30 KCG 308 -10 340 -16 327 -8 328 -16 029 +55 343 -29
Aug 5 283 +58 NIA 313 -8 345 -14 332 -6 334 -15 037 +57 348 -27
Aug 10 284 +58 317 -7 318 -6 349 -13 335 -5 339 -14 043 +58 352 -26
Aug 15 285 +59 322 -7 352 -12 339 -4 345 -13 050 +59
Aug 20 286 +59 327 -6 AUR 356 -11 343 -3 057 +59
Aug 25 288 +60 332 -5 076 +42 347 -2 065 +60
Aug 30 289 +60 337 -5 082 +42 DAU
Sep 5 088 +42 055 +46 SPI
Sep 10 060 +47 357 -5
Sep 15 066 +48 001 -3
Sep 20 071 +48 005 -1
Sep 25 NTA STA 077 +49 009 0
Sep 30 021 +11 023 +5 ORI 083 +49 013 +2
Oct 5 025 +12 027 +7 085 +14 089 +49 GIA
Oct 10 029 +14 031 +8 088 +15 095 +49 262 +54
Oct 15 034 +16 035 +9 091 +15 EGE
Oct 20 038 +17 039 +11 094 +16 099 +27
Oct 25 043 +18 043 +12 098 +16 104 +27
Oct 30 047 +20 047 +13 101 +16 109 +27
Nov 5 053 +21 052 +14 105 +17
Nov 10 058 +22 056 +15 LEO AMO
Nov 15 062 +23 060 +16 150 +23 112 +2
Nov 20 067 +24 064 +16 XOR 153 +21 116 +1
Nov 25 072 +24 069 +17 075 +23 120 0 MON PUP PHO
Nov 30 080 +23 HYD 091 +8 120 -45 014 -52
Dec 5 COM GEM 085 +23 122 +3 096 +8 122 -45 018 -53
Dec 10 169 +27 108 +33 090 +23 126 +2 100 +8 125 -45 022 -53
Dec 15 173 +26 113 +33 094 +23 130 +1 URS 104 +8 128 -45
Dec 20 177 +24 118 +32 217 +75
Shower Activity Max lambda Radiant Best Observed Rate
Date 2000.0 al. de. 50°N 35°S
° ° °
Cap/Sagittarids Jan 13-Feb 04 Feb 02 312.5 299 -15 11h-14h 09h-14h medium
chi-Capricornids Jan 29-Feb 28 Feb 14 324.7 315 -24 10h-13h 08h-15h low
Piscids (Apr.) Apr 08-Apr 29 Apr 20 030.3 007 +7 07h-14h 08h-13h low
delta-Piscids Apr 24-Apr 24 Apr 24 034.2 011 +12 07h-14h 08h-13h low
epsilon-Arietids Apr 24-May 27 May 08 048.7 044 +21 08h-15h 10h-14h low
Arietids (May) May 04-Jun 06 May 16 055.5 037 +18 08h-15h 09h-13h low
o-Cetids May 05-Jun 02 May 19 059.3 028 -4 07h-13h 07h-13h medium
Arietids May 22-Jul 02 Jun 07 076.7 044 +24 06h-14h 08h-12h high
zeta-Perseids May 20-Jul 05 Jun 09 078.6 062 +23 07h-15h 09h-13h high
beta-Taurids Jun 05-Jul 17 Jun 28 096.7 086 +19 08h-15h 09h-13h medium
gamma-Leonids Aug 14-Sep 12 Aug 25 152.2 155 +20 08h-16h 10h-14h low
Sextantids Sep 09-Oct 09 Sep 27 184.3 152 0 06h-12h 06h-13h medium
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