IMO Meteor Shower Calendar 2003

• Introduction
• Highlights January to March
• Quadrantids
• alpha-Centaurids
• delta-Leonids
• Highlights April to June
• Lyrids
• pi-Puppids
• eta-Aquarids
• June Bootids
• Highlights July to September
• Pegasids
• Aquarids
• alpha-Aurigids
• Piscids
• Highlights October to December
• Orionids
• Leonids
• alpha-Monocerotids
• chi-Orionids
• Coma Berenicids
• Ursids
• Radiant sizes and meteor plotting
• Optimum radiant diameters for shower association
• Error limits for the angular velocity
• Angular meteor velocities
• Abbreviations
• Tables
• Lunar phases for 2003
• Working list of visual meteor showers
• Radiant positions during the year in alpha and delta
• Working list of daytime radio meteor streams
• Useful addresses

Welcome to the 2003 International Meteor Organization (IMO) Meteor Shower Calendar. The year sees two of the "big three" major showers - the Perseids and Geminids - lost to bright moonlight, but the third, the Quadrantids, are well-placed, along with the alpha-Centaurids, eta-Aquarids, and Southern delta-Aquarids. Minor or uncertain sources like the delta-Leonids, June Bootids, alpha-Aurigids, alpha-Monocerotids, Coma Berenicids and Ursids also enjoy often moonless skies, amongst others. What the Leonids may do in 2003 needs checking as well. Do not forget that monitoring of meteor activity should ideally be carried on throughout the rest of the year, 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 timing 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, video, visual 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 (see Table 5, 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, plus some of their own, 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 and video 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!

For the major showers, the year begins with a superb northern-hemisphere Quadrantid return, and the southern-hemisphere alpha-Centaurids in early February are also Moon-free at their best. The minor streams enjoy mixed fortunes. The delta-Cancrids are lost to full Moon (peak January 17; full Moon January 18!), though their possibly earlier maximum on January 11 (sol = 291°) has the gibbous Moon setting between local midnight and 1h and would be worth checking. By contrast, the delta-Leonids are mostly moonless. The diffuse ecliptical stream complex of the Virginids gets underway by late January, running through to mid April, probably producing several low, and poorly-observed, maxima in March or early April. The interesting late January to early February spell, during which several new minor showers have been suggested in recent years, is partly Moon-free, but effectively only between last and first quarter Moon, January 25 to February 9, not ideal, especially for most of the January 20-27 period. Mid-March brings a badly moonlit spell for checking on the southern-hemisphere gamma-Normids, whose details are most uncertain. A maximum may occur on either March 14 or 17 from recent results, with ZHRs virtually undetectable more than a day or two away from the peak. Daylight radio shower peaks are theoretically due from the Capricornids/Sagittarids around February 1, 20h UT, and the chi-Capricornids on February 13, 21h UT. Recent radio results suggest the Cap/Sgr maximum may variably fall up to 2 or 3 days later than this however, while activity near the expected chi-Capricornid peak has tended to be slight and perhaps a day or so later in 1999-2001. Both showers have radiants < 10°-15° west of the Sun at maximum, so cannot be regarded as visual targets even from the southern hemisphere.

Active       : January 1-5; 
Maximum      : January 4, 0h UT (sol = 283.16);
ZHR          = 120 (can vary ~ 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 0h local time alpha = 150°, delta = +70°; 
               after 0h local time alpha = 180°, delta = +40° 
               and alpha = 240°, delta = +70° (beta > 40° N).

An excellent return of the Quadrantids for northern observers starts the year perfectly, with an expected peak around midnight UT on January 3-4. The waxing crescent Moon is less than 28 hours old then, so produces no problems at all. For many northern locations the shower's radiant is circumpolar, in northern Bootes (see Fig. 1), but it attains a useful elevation only after local midnight, rising higher in the sky towards morning twilight. Consequently Europe eastwards to the Near East, and North Africa, are the most favored places to catch the shower's best this year. 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 places.

The maximum time given above is based on the best-observed return of the shower ever analyzed, in IMO 1992 data, confirmed by radio results in 1996, 1997, 1999 and 2001. The peak itself is normally short-lived, and can be easily missed in just a few hours of poor northern-winter weather, 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. Oddly, 2000 and 2001 saw primarily radio maxima following the main visual one by some 9-12 hours. Visual confirmation of any repeat near this time in 2003 would fall for sites in the Far Eastern eastwards to North Pacific regions.

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 outside 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, 10h20m UT (sol = 319.2);
ZHR          = variable, usually ~ 6, but may reach 25+;
Radiant      : alpha = 210°, delta = -59°, Radiant drift: see Table 6;
V            = 56 km/s; 
r            = 2.0.

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 -4). 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.

Thanks to their brilliance, even a normal alpha-Centaurid return is worth looking out for, with almost one-third of shower meteors leaving persistent trains. The radiant is nearly circumpolar for much of the sub-equatorial inhabited Earth, and is at a useful elevation from late evening onwards, good news this year with the Moon a waxing crescent just before first quarter, setting by 23h local time on February 8 for most typical southern hemisphere sites.

Active       : February 15-March 10; 
Maximum      : February 25 (sol = 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 = 00° (beta < 10° N).

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 an advantage for covering this shower, though southern hemisphere watchers should not ignore it, as they are better-placed to note many of the other Virginid radiants. The waning crescent Moon rises between about 3h-5h local time for typical northern sites, but around midnight for the mid-southern hemisphere, though it should not be too great a distraction. The delta-Leonid radiant is well on view for most of the night near its peak.

Active       : April 16-25; 
Maximum      : April 22, 22h00m UT (sol = 32.32, but may vary - see text);
ZHR          = 18 (can be variable, up to 90);
Radiant      : alpha = 271°, delta = +34°; Radiant drift: see Table 6;
V            = 49 km/s; 
r            = 2.1;
TFC          : alpha = 262°, delta = +16° and 
               alpha = 282°, delta = +19° (beta > 10° S).

Audrius Dubietis and Rainer Arlt published a detailed investigation of the Lyrids in IMO results from 1988-2000 in 2001, the most detailed examination of the shower in modern times. Several fresh features were found, the most important of which was to redefine the maximum time as variable from year to year between sol = 32.0-32.45 (equivalent to 2003 April 22, 14h10m UT to April 23, 01h15m UT), with an ideal time of sol = 32.32. Although the mean peak ZHR was 18 over the thirteen years, actual peak ZHRs varied dependent on when the maximum time occurred. A peak at the ideal time produced the highest ZHRs, ~23, while the further the peak happened from this ideal, the more the ZHRs were reduced, to as low as ~14. (The last very high maximum occurred outside the examined interval, in 1982 over the USA, when a short-lived ZHR of 90 was recorded.) While generally thought of as having a short, quite sharp, maximum, this latest work revealed the shower's peak length was variable too. This was measured by how long ZHRs were above half the maximum value, the Full-Width-Half-Maximum (FWHM) time. It varied from 14.8h in 1993 to 61.7h in 2000, with a mean value of 32.1h. Best rates are normally achieved for just a few hours however. One other aspect found, confirming data from earlier in the 20th century was that occasionally, as their highest rates occurred, the Lyrids produced a short-lived increase of fainter meteors. Overall, the unpredictability of the shower in any given year always makes the Lyrids worth watching, since we cannot say when the next unusual return may occur.

The shower is best viewed from the northern hemisphere, but it is visible from many sites north and south of the equator, and is suitable for all forms of observation. As the shower's radiant rises during the night, watches can be usefully carried out from about 22h 30^\m local time onwards. The waning gibbous Moon rises between ~ 2h-3h local time for mid-northern sites on April 22-23, giving several hours of darker skies for observers before this. The earlier moonrise south of the equator is much less favorable. The ideal maximum time, if it recurs, would be best-seen from sites in central Asia westwards to eastern Europe, but other maximum times are perfectly possible, as noted above.

Active       : April 15-28; 
Maximum      : April 24, 3h UT (sol = 33.5);
ZHR          = periodic, up to around 40;
Radiant      : alpha = 110°, delta = -45°; Radiant drift: see Table 6;
V            = 18 km/s; 
r            = 2.0;
TFC          : alpha = 135°, delta = -55° and 
               alpha = 105°, delta = -25° (beta < 20° N).

This is a young stream produced by Comet 26P/Grigg-Skjellerup, and shower activity has only been detected from it since 1972. Notable short-lived shower maxima of around 40 meteors per hour took place in 1977 and 1982, both years when the parent comet was at perihelion, but before 1982, little activity had been seen at other times. In 1983, a ZHR of about 13 was reported, perhaps suggesting that material has begun to spread further along the comet's orbit, as theory predicts. Comet Grigg-Skjellerup reached perihelion last in October 2002, so this will be an interesting year to check for whatever happens.

The shower is best-seen from the southern hemisphere, with useful observations mainly possible before local midnight, as the radiant is very low to setting after 1h local time. The last quarter Moon will be rising around 23h-0h local time from such locations on April 23-24, which should work out reasonably well for watchers. Well-placed sites are likely to be across Central and South America, if the maximum time proves correct. So far, visual and radio data have been collected on the shower, but the slow, bright nature of the meteors makes them ideal photographic subjects too. No telescopic or video data have been reported in any detail as yet.

Active       : April 19-May 28; 
Maximum      : May 6, 11h30m UT (sol = 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).

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 low, eta-Aquarid meteors tend to have very long paths, which can mean observers underestimate the apparent speeds of the meteors, so extra care is needed when making such angular speed reports.

A relatively broad maximum, sometimes with a variable number of submaxima, usually occurs in early May. ZHRs are generally above 30 between about May 3-10, based on IMO observations during 1988-1997, analyzed by Tim Cooper, and confirmed by visual and radio observations since. The waxing crescent Moon on May 6 will have set long before radiant-rise, so conditions are ideal in 2003. All forms of observing can be used to study the eta-Aquarids, with radio work allowing activity to be followed even from many northern latitude sites throughout the daylight morning hours. The radiant culminates at about 8h local time.

Active       : June 26-July 2; 
Maximum      : June 27, 19h 30m UT (sol = 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).

Following the wholly unexpected strong return of this shower in 1998, when ZHRs of 50-100+ were visible for more than half a day, we reintroduced this source to the Working List of Visual Meteor Showers, and encourage all observers to routinely monitor the expected activity period in case of future outbursts. Prior to 1998, only three returns of the shower had been detected, in 1916, possibly in 1921 and 1927, and with no significant reports between 1928-1997, it seemed probable the stream no longer encountered Earth. The dynamics of the stream are poorly understood. The shower's parent comet 7P/Pons-Winnecke was at perihelion in January 1996 and again in May 2002. Its orbit currently lies around 0.24 astronomical units outside the Earth's at its closest approach, and the 1998 outburst is thought to be caused by old material in mean-motion resonance with Jupiter. We pass the resonant cloud in 2004 again and may already hope for heightened rates in 2003 (June 27, 19h UT). The radiant is at a useful elevation for most of the short summer night in the northern hemisphere (only), and the waning crescent Moon, less than two days from new on June 27-28, will present no problems for watching.

Active       : July 7-13; 
Maximum      : July 10 (sol = 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, which with a waxing gibbous Moon on July 10, will allow most observers from mid-northern latitudes southwards a 1h+ window of darker skies between moonset and dawn twilight starting (local moonset is around 0:30-1:30 at mid-northern latitudes, or between 3h-4h for typical southern hemisphere sites). The maximum ZHR is generally low, and swift, faint meteors can be expected, favoring telescopic observing.

Piscis Austrinids & Aquarid/Capricornid Complex

Piscis Austrinids

Active       : July 15-August 10; 
Maximum      : July 28 (sol = 125°); 
ZHR          = 5;
Radiant      : alpha = 341°, delta = -30°, Radiant drift: see Table 6;
V            = 35 km/s; 
r            = 3.2;
TFC          : alpha = 255° to 000°, delta = 00° to +15°, 
               choose pairs separated by about 30° in alpha (beta < 30° N).

Southern delta-Aquarids

Active       : July 12-August 19; 
Maximum      : July 28 (sol = 125°); 
ZHR          = 20;
Radiant      : alpha = 339°, delta = -16°, Radiant drift: see Table 6;
V            = 41 km/s; 
r            = 3.2;
TFC          : alpha = 255° to 000°, delta = 00° to +15°, 
               choose pairs separated by about 30° in alpha (beta < 40° N).

alpha-Capricornids

Active       : July 3-August 15; 
Maximum      : July 30 (sol = 127°); 
ZHR          = 4;
Radiant      : alpha = 307°, delta = -10°, Radiant drift: see Table 6;
V            = 23 km/s; 
r            = 2.5;
TFC          : alpha = 255° to 000°, delta = 00° 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°).

Southern iota-Aquarids

Active       : July 25-August 15; 
Maximum      : August 4 (sol = 132°); 
ZHR          = 2;
Radiant      : alpha = 334°, delta = -15°, Radiant drift: see Table 6;
V            = 34 km/s; 
r            = 2.9;
TFC          : alpha = 255° to 000°, delta = 00° to +15°, 
               choose pairs separated by about 30° in alpha (beta < 30° N).

Northern iota-Aquarids

Active       : August 11-31; 
Maximum      : August 20 (sol = 147°); 
ZHR          = 3;
Radiant      : alpha = 327°, delta = -06°; Radiant drift: see Table 6;
V            = 31 km/s; 
r            = 3.2;
TFC          : alpha = 255° to 000°, delta = 00° to +15°, 
               choose pairs of fields separated by about 30° in alpha (beta < 30° N).

Figure 6: Radiant position of the Piscis Austrinids, Northern and Southern iota-Aquarids

The Aquarids and Piscis Austrinids are all showers 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 ~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. Visual watchers in particular should plot any potential shower 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 2003 new Moon on July 29 favors all the July-August maxima from these sources except the Northern delta-Aquarids. In late August, the Northern iota-Aquarids showed an ill-defined maximum between sol = 148°-151° in 1988-1995 results, which could mean the highest rates (even so, very weak) happen several days after the suspected peak time given here. The early-rising last quarter Moon on August 20 for northern hemisphere sites makes more southerly sites favored this year, but moonlight conditions will improve even a few days later in the month. All these radiants are above the horizon for much of the night.

Active       : August 25-September 8; 
Maximum      : September 1, 12h UT (sol= 158.6); 
ZHR          = 7;
Radiant      : alpha = 84°, delta = +42°, Radiant drift: see Table 6;
V            = 66 km/s; 
r            = 2.6;
TFC          : alpha = 052°, delta = +60°; alpha = 043°, delta = +39° 
               and alpha = 023°, delta = +41° (beta > 10° S).

[image:670

This shower and its less-favorable nearby source, the delta-Aurigids, 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 ~30-40 in 1935, 1986 and 1994, although they have not been monitored regularly until very recently, so other outbursts may have been missed. Audrius Dubietis and Rainer Arlt published a detailed investigation of IMO data between 1986-2000 on this shower in 2002, following which a few minor amendments have been made to the shower parameters given above and used in the Working List of Visual Meteor Showers below. The very tiny number of reports on the 1986 and 1994 outbursts (just three observers in total!) meant almost no useful details could be derived on these regrettably, reinforcing the need for more observers to be active in a favorable year such as 2003. The radiant reaches a useful elevation after 23h-00h local time, so lunar circumstances are ideal, with a waxing crescent Moon setting by mid-evening. 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.

Active       : September 1-30; 
Maximum      : September 20 (sol = 177°); 
ZHR          = 3;
Radiant      : alpha = 005°, delta = -01°; Radiant drift: see Table 6;
V            = 26 km/s; 
r            = 3.0;
TFC          : alpha = 340° to 020°, delta = -15° to +15°, 
               choose pairs of fields separated by about 30° in alpha (beta any).

Audrius Dubietis carried out an examination of IMO data on the Piscids (earlier known as the Southern Piscids; no other Piscid radiant has been clearly defined as visually active for many years) between 1985-1999 in early 2001, which essentially confirmed the current details on the shower are correct, including that this is another poorly-studied minor shower! Its radiant near the maximum is very close to the March equinox point in the sky, and consequently, it can be observed equally well from either hemisphere throughout the night near the September equinox. This year, the waning crescent Moon gives at least the first half of the night with dark skies for observers (longer in the southern hemisphere). Telescopic and video methods can be usefully employed to study the Piscids, along with methodical visual plotting.

Active       : October 2-November 7; 
Maximum      : October 21, 21h UT (sol = 208°); 
ZHR          = 20;
Radiant      : alpha = 095°, delta = +16°; Radiant drift: see Table 6;
V            = 66 km/s; 
r            = 2.9;
TFC          : alpha = 100°, delta = +39° and 
               alpha = 075°, delta = +24° (beta > 40° N); 
               or alpha = 080°, delta = +01° and 
               alpha = 117°, delta = +01° (beta < 40° N).

October's waning crescent Moon partly favors the Orionids near their best. They are noted for having several maxima other than the main one above, with activity sometimes remaining almost constant for several consecutive nights centered on this peak. In 1993 and 1998, a submaximum as strong as the normal peak was detected on October 17-18 from Europe, for instance. All observers should be aware of these possibilities, though covering October 17-18 in dark skies will not be possible in 2003. Several subradiants have been reported in the past, but recent video work suggests the radiant is far less complex; photographic, telescopic and video work to confirm this would be useful, as visual observers have clearly had problems with this shower's radiant determination before. With a radiant near the celestial equator, the shower can be seen from most of the globe, and observations are possible from midnight onwards in both hemispheres, perhaps a little before in the north.

Active       : November 14-21; 
Maximum      : November 18, 2h30m UT (sol = 235.27); 
ZHR          = 100+?;
Radiant      : alpha = 153°, delta = +22°; Radiant drift: see Table 6;
V            = 71 km/s; 
r            = 2.5;
TFC          : alpha = 140°, delta = +35° and 
               alpha = 129°, delta = +06° (beta > 35° N); or
               alpha = 156°, delta = -03° and 
               alpha = 129°, delta = +06° (beta < 35° N).
PFC          : alpha = 120°, delta = +40° before 0h local time (beta > 40° N); 
               alpha = 120°, delta = +20° before 4h local time and 
               alpha = 160°, delta = 00° after 4h local time (beta > 00° N); 
               alpha = 120°, delta = +10° before 0h local time and 
               alpha = 160°, delta = -10° (beta < 00° N).

Following the series of strongly enhanced to storm level returns of the Leonids since 1998, associated with the 1998 perihelion passage of the shower's parent comet 55P/Tempel-Tuttle, 2003 may well see falling rates as the shower begins its decline to more "normal" levels of activity. Certainly, no very strongly enhanced activity is predicted, although as meteor enthusiasts know well, surprises can occur from even the best-known showers on occasion! Observers should be alert to covering whatever the shower produces, as following the post-storm phases after this best-ever observed series of storm returns is as vital to our understanding of the stream as seeing the storms themselves.

The Leonid radiant rises usefully only around local midnight (or indeed afterwards south of the equator), not good news, as the last quarter Moon in Leo rises around the same time this year on November 17-18. Observers should persevere however, facing away from the Moon where possible. If the peak occurs at the nodal crossing time (above), it will favor sites across Europe, Africa and the Near East especially, but other peak times cannot be excluded, and observers should be watching for as much of November 16-17 to 19-20 as conditions will allow, in case something unexpected happens. All observing techniques can be usefully employed.

Active       : November 15-25; 
Maximum      : November 22, 2h45m UT (sol = 239.32);
ZHR          = variable, usually ~ 5, but may produce outbursts to ~ 400+;
Radiant      : alpha = 117°, delta = +01°; 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 = 098°, delta = +06° (beta < 20° N).

Another late-year shower capable of producing surprises, the alpha-Monocerotids gave their most recent brief outburst in 1995 (the top EZHR, ~ 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 (two more years to go!), so all observers should continue to monitor this source closely. New Moon on November 23 makes this an ideal year for detailed scrutiny. The radiant is well on view from either hemisphere after about 23h local time, so the expected peak falls especially well for sites across the Near East, Africa and all of Europe.

Active       : November 26-December 15; 
Maximum      : December 2 (sol = 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).

A weak visual stream, but one moderately active telescopically. Some brighter meteors have been photographed from it 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 in late November. 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. It is well on display in both hemispheres throughout the night, and with the waxing gibbous Moon setting between 0h30m-1h30m local time in either hemisphere on December 2, the second half of the night should be fully employed to cover the stream.

Active       : December 12-January 23; 
Maximum      : December 20 (sol = 268°); 
ZHR          = 5;
Radiant      : alpha = 175°, delta = +25°; Radiant drift: see Table 6;
V            = 65 km/s; 
r            = 3.0;
TFC          : alpha = 180°, delta = +50° and 
               alpha = 165°, delta = +20° before 3h local time, 
               alpha = 195°, delta = +10° and 
               alpha = 200°, delta = +45° after 3h local time (beta > 20° N).

A weak minor shower that is usually observed only during the Geminid and Quadrantid epochs, but which needs more coverage at other times too, especially to better define its maximum. The shower is almost unobservable from the southern hemisphere, so northern watchers must brave the winter cold to improve our knowledge of it, especially this year as its expected peak benefits from a nearly-new Moon. The radiant is at a useful elevation from local midnight onwards.

Active       : December 17-26; 
Maximum      : December 23, 1h UT (sol = 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 = 063°, delta = +84° and 
               alpha = 156°, delta = +64° (beta 30° to 40° N).

A very poorly-observed northern hemisphere shower, but one which has produced at least two major outbursts in the past 60 years, in 1945 and 1986. Several other rate enhancements, recently in 1988, 1994 and 2000, 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 sol = 270.8, for instance, which might suggest a slightly later maximum time in 2003 of December 23, 3h UT, while the 2000 enhancement was seen surprisingly strongly (EZHR ~ 90) by video at sol = 270.78 (equivalent to 2003 December 23, 2h40m UT), although the visual enhancement was much less, ZHR ~ 30±5. 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. New Moon makes this a perfect year for seeing whatever happens. The expected peak times favor northerly sites between western Asia westwards to eastern North America.

If you are not observing during a major-shower maximum, it is essential to associate meteors with their radiants correctly, since the total number of meteors will be small for each source. Meteor plotting allows shower association by more objective criteria after your observation than the simple imaginary back-prolongation of paths under the sky. With meteors plotted on gnomonic maps, you can trace them back to their radiants by extending their straight line paths. If a radiant lies on another chart, you should find common stars on an adjacent chart to extend this back-prolongation correctly.

How large a radiant should be assumed for shower association? The real physical radiant size is very small, but visual plotting errors cause many true shower meteors to miss this real radiant area. Thus we have to assume a larger effective radiant to allow for these errors. Unfortunately, as we enlarge the radiant, so more and more sporadic meteors will appear to line up accidentally with this region. Hence we have to apply an optimum radiant diameter to compensate for the plotting errors loss, but which will not then be swamped by sporadic meteor pollution. Table 1 gives this 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 path-direction is not the only criterion for shower association. The angular velocity of the meteor should match the expected speed of the given shower meteors according to their geocentric velocities. Angular velocity estimates should be made in degrees per second (°/s). To do this, make the meteors you see move for one second in your imagination at the speed you saw them. 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 for such estimates are given in Table 2.

angular velocity °/s     5   10   15   20   30
permitted error  °/s     3    5   6     7    8

If you find a meteor in your plots which passes the radiant within the diameter given by Table 1, check its angular velocity. Table 3 gives the angular speeds for a few geocentric velocities, which can then 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 10.0
40°   1.6  3.2  5.9  8.0  9.3    2.6  5.0  9.5 13.0 15.0    3.7  6.7 13.0 17.0 20.0
60°   2.2  4.3  8.0 11.0 13.0    3.5  6.8 13.0 17.0 20.0    4.6  9.0 17.0 23.0 26.0
90°   2.5  4.9  9.3 13.0 14.0    4.0  7.9 15.0 20.0 23.0    5.3 10.0 20.0 26.0 30.0

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, an equivalent ZHR (EZHR) is used measuring the activity as if it would have lasted for an hour.

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 2     January 10     January 18     January 25 
February 1    February 9     February 16    February 23 
March 3       March 11       March 18       March 25 
April 1       April 9        April 16       April 23 
May 1         May 9          May 16         May 23 
May 31        June 7         June 14        June 21 
June 29       July 7         July 13        July 21 
July 29       August 5       August 12      August 20 
August 27     September 3    September 10   September 18 
September 26  October 2      October 10     October 18 
October 25    November 1     November 9     November 17 
November 23   November 30    December 8     December 16 
December 23   December 30   

Shower                    Activity         Maximum        Radiant   V    r   ZHR 
                           Period        Date  lambda  alpha delta
                                                 °       °     °   km/s
Quadrantids (QUA)        Jan 01-Jan 05  Jan 04  283.16  230   +49  41   2.1  120
delta-Cancrids (DCA)     Jan 01-Jan 24  Jan 17  297     130   +20  28   3.0    4
alpha-Centaurids (ACE)   Jan 28-Feb 21  Feb 08  319.2   210   -59  56   2.0    6
delta-Leonids (DLE)      Feb 15-Mar 10  Feb 24  336     168   +16  23   3.0    2
gamma-Normids (GNO)      Feb 25-Mar 22  Mar 14  353     249   -51  56   2.4    8
Virginids (VIR)          Jan 25-Apr 15 (Mar 25)  (4 )   195   -04  30   3.0    5
Lyrids (LYR)             Apr 16-Apr 25  Apr 22   32.32  271   +34  49   2.1   18
pi-Puppids (PPU)         Apr 15-Apr 28  Apr 24   33.5   110   -45  18   2.0  var
eta-Aquarids (ETA)*      Apr 19-May 28  May 06   45.5   338   -01  66   2.7   60
Sagittarids (SAG)        Apr 15-Jul 15 (May 20) (59 )   247   -22  30   2.5    5
June Bootids  (JBO)      Jun 26-Jul 02  Jun 27   95.7   224   +48  18   2.2  var
Pegasids (JPE)           Jul 07-Jul 13  Jul 10  107.5   340   +15  70   3.0    3
July Phoenicids (PHE)    Jul 10-Jul 16  Jul 13  111      32   -48  47   3.0  var
Piscis Austrinids (PAU)  Jul 15-Aug 10  Jul 28  125     341   -30  35   3.2    5
South. delta-Aqr. (SDA)  Jul 12-Aug 19  Jul 28  125     339   -16  41   3.2   20
alpha-Capricornids (CAP) Jul 03-Aug 15  Jul 30  127     307   -10  23   2.5    4
South. iota-Aqr. (SIA)   Jul 25-Aug 15  Aug 04  132     334   -15  34   2.9    2
North. delta-Aqr. (NDA)  Jul 15-Aug 25  Aug 09  136     335   -05  42   3.4    4
Perseids (PER)*          Jul 17-Aug 24  Aug 13  140.0    46   +58  59   2.6  110
kappa-Cygnids (KCG)      Aug 03-Aug 25  Aug 18  145     286   +59  25   3.0    3
North. iota-Aqr. (NIA)   Aug 11-Aug 31  Aug 20  147     327   -06  31   3.2    3
alpha-Aurigids (AUR)     Aug 25-Sep 08  Sep 01  158.6    84   +42  66   2.6    7
delta-Aurigids (DAU)     Sep 05-Oct 10  Sep 09  166      60   +47  64   3.0    6
Piscids (SPI)            Sep 01-Sep 30  Sep 20  177       5   -01  26   3.0    3
Draconids (GIA)          Oct 06-Oct 10  Oct 09  195.4   262   +54  20   2.6  var
epsilon-Geminids (EGE)   Oct 14-Oct 27  Oct 18  205     102   +27  70   3.0    2
Orionids (ORI)           Oct 02-Nov 07  Oct 21  208      95   +16  66   2.9   20
Southern Taurids (STA)   Oct 01-Nov 25  Nov 05  223      52   +13  27   2.3    5
Northern Taurids (NTA)   Oct 01-Nov 25  Nov 12  230      58   +22  29   2.3    5
Leonids (LEO)*           Nov 14-Nov 21  Nov 18  235.27  153   +22  71   2.5  100+
alpha-Monocerotids (AMO) Nov 15-Nov 25  Nov 22  239.32  117   +01  65   2.4  var
chi-Orionids (XOR)       Nov 26-Dec 15  Dec 02  250      82   +23  28   3.0    3
Dec Phoenicids (PHO)     Nov 28-Dec 09  Dec 06  254.25   18   -53  22   2.8  var
Puppid/Velids (PUP)      Dec 01-Dec 15 (Dec 07)(255 )   123   -45  40   2.9   10
Monocerotids (MON)       Nov 27-Dec 17  Dec 09  257     100   +08  42   3.0    3
sigma-Hydrids (HYD)      Dec 03-Dec 15  Dec 12  260     127   +02  58   3.0    2
Geminids (GEM)           Dec 07-Dec 17  Dec 14  262.0   112   +33  35   2.6  120
Coma Berenicids (COM)    Dec 12-Jan 23  Dec 20  268     175   +25  65   3.0    5
Ursids (URS)             Dec 17-Dec 26  Dec 23  270.7   217   +76  33   3.0   10

         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   EGE    262 +54
Oct 15 034 +16 035  +9 091 +15         099 +27
Oct 20 038 +17 039 +11 094 +16         104 +27
Oct 25 043 +18 043 +12 098 +16         109 +27
Oct 30 047 +20 047 +13 101 +16
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 01 312.5 299 -15  11h-14h 09h-14h medium
chi-Capricornids Jan 29-Feb 28 Feb 13 324.7 315 -24  10h-13h 08h-15h low
Piscids (April)  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 09 048.7 044 +21  08h-15h 10h-14h low
Arietids (May)   May 04-Jun 06 May 16 055.5 037 +18  08h-15h 09h-13h low
omicron-Cetids   May 05-Jun 02 May 20 059.3 028  -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

Useful addresses

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                              NL-2264 SN Leidschendam, 
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                              Hilo, HI 96720, 
                              USA.
                              e-mail: tele@imo.net

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                              D-15366 Hönow, 
                              Germany.
                              e-mail: video@imo.net

Visual Commission:            Rainer Arlt, 
                              Friedenstrasse 5, 
                              D-14109 Potsdam, 
                              Germany.
                              e-mail: visual@imo.net

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