IMO Meteor Shower Calendar 1998

compiled by Alastair McBeath

based on data in IMO Monograph No.2: Handbook for Visual Meteor Observers,
edited by Jürgen Rendtel, Rainer Arlt and Alastair McBeath, IMO, 1995,

with additional contributions from Rainer Arlt, Marc de Lignie,
Jürgen Rendtel and Paul Roggemans.

Layout by André Knöfel.

Prepared for WWW by Sirko Molau

IMO’s Meteor Shower Calendar for 1998 contains the following items:



Introduction

   
     Welcome to the 1998 International Meteor Organization (IMO) Meteor Shower   
     Calendar. This year promises to be an extremely interesting one, with most   
     major showers free from moonlight interference (except the eta-Aquarids and   
     Perseids), the prospect of a Draconid return in October, and a possible   
     meteor storm from the Leonids in November. 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 received little   
     attention in recent years). 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 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 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 less popular, although   
     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 have been dynamically applied 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   
     already 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!   
     


January to March

   
     The opening quarter of the year brings several low activity showers,   
     including the first of the year's main diffuse ecliptical stream complexes,   
     the Virginids, active from late January to mid-April. Of the two better   
     showers, only the northern-hemisphere Quadrantids in early January are free   
     from moonlight. The other, the alpha-Centaurids, a sometimes good southern   
     hemisphere shower (maximum around February 7, 16h UT) is too close to full   
     Moon for non-radio observations. The minor delta-Cancrids in mid-January   
     lose out too to a bright Moon, along with the gamma-Normids in mid-March.   
     Daylight radio peaks are due from the Capricornids/Sagittarids around 13h   
     UT on February 1, and the chi-Capricornids on February 13, probably around   
     14h UT. Neither radio shower has been well-observed in recent times, and as   
     both have radiants under 10°-15° west of the Sun at maximum, they   
     cannot be regarded as visual targets even from the southern hemisphere.   
        
     


Quadrantids

   
     Active  : January 1-5;   
     Maximum  : January 3, 17h UT (lambda = 283.16°);   
     ZHR   = 120 (can vary around 60-200);   
     Radiant  : alpha = 230°, delta = +49°;   
     Radiant drift: see Table 3;   
     Radius  : 5° at maximum;   
     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 of the Quadrantids   
        
     [image:843]   
        
     The year commences with a good return of the Quadrantids for northern   
     hemisphere observers, as the Moon will be a waxing crescent setting by the   
     local late evening hours of January 3. 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. The Moon will thus present no problems in 1998.   
     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 analysed, from IMO 1992 data, confirmed by radio results in   
     1996 and 1997, and a repeat of which time in 1998 would favour sites from   
     Alaska and the Northern Pacific islands to Far Eastern Siberia, China and   
     Japan. The peak itself is 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. 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.   
        
     


delta-Leonids

   
     Active  : February 15 - March 10;   
     Maximum  : February 24 (lambda = 336°);   
     ZHR   = 2;   
     Radiant  : alpha = 168°, delta = +16°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     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 2: Radiant position of the delta-Leonids   
        
     [image:53]   
        
     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, whose radiant is well on view for most of the night   
     near the peak, close to the "Sickle" or "Head" of Leo, but southern   
     hemisphere watchers should not ignore it, as they are better-placed to note   
     many of the other Virginid radiants. With the Moon just two days before new   
     at the shower's maximum, conditions could scarcely be better for observing   
     it.   
     

April to June

Meteor activity picks up towards the April-May boundary, with showers like the Lyrids, p-Puppids and h-Aquarids, and only this latter source suffers from moonlight this year. During May and June, most of the activity is in the daytime sky, with six shower peaks expected during this time. Although a few shower members from the o-Cetids and Arietids have been reported from tropical and southern hemisphere sites visually in previous years, sensible activity calculations cannot be carried out from such observations. For radio observers, the expected UT maxima for these showers and the Moon- affected h- Aquarids are as follows: April Piscids -- April 20, 13h UT; delta-Piscids -- April 24, 13h UT; eta-Aquarids -- May 6, 04h UT; epsilon-Arietids -- May 9, 12h UT; May Arietids -- May 16, 13h UT; o-Cetids -- May 20, 11h UT; Arietids -- June 7, 15h UT; zeta-Perseids -- June 9, 14h UT; beta-Taurids -- June 28, 14h UT. The ecliptical complexes continue with some late Virginids and the best from the minor Sagittarids in May-June.


Lyrids

   
     Active  : April 16-25;   
     Maximum  : April 22, 10h UT (lambda = 32.1°);   
     ZHR   = 15 (can be variable, up to 90);   
     Radiant  : alpha = 271°, delta = +34°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     V   = 49 km/s;   
     r   = 2.9;   
     TFC   : alpha = 262°, delta = +16° and   
         alpha = 282°, delta = +19° (beta>10° S).   
        
     Figure 3: Radiant position of the Lyrids   
        
     [image:54]   
        
     The Lyrids are best viewed from the northern hemisphere, but they are   
     observable from many sites either north or south of the equator, and are   
     suitable for all forms of observation. Maximum rates are usually attained   
     for only an hour or two at best, although in 1996, mean peak ZHRs of 15-20   
     persisted for around 8-12 hours. The ZHR can be rather erratic at times, a   
     variability also seen in 1996, when rates ranged between 10-30 from hour to   
     hour during the peak. The last high maximum occurred in 1982 over the USA,   
     when a very short-lived peak ZHR of 90 was recorded. This unpredictability   
     always makes the Lyrids a shower to watch, since we cannot say when the   
     next unusual return may occur.   
        
     As the shower's radiant rises during the night, watches can be usefully   
     carried out from about 22:30 local time onwards. This year, the Moon will   
     be a waning crescent in Capricornus/Aquarius for the peak, and will rise   
     not long before dawn, so skies should remain dark for much of the night.   
     The predicted maximum should favour sites across North America if correct,   
     but variations in the stream could mean this is not the case in actuality.   
        
     


pi-Puppids

   
     Active  : April 15-28;   
     Maximum  : April 23, 20h UT (lambda = 33.5°);   
     ZHR   : periodic, up to around 40;   
     Radiant  : alpha = 110°, delta = -45°;   
     Radiant drift: see Table 3;   
     radius  : 5°;   
     V   = 18 km/s;   
     r   = 2.0;   
     TFC   : alpha = 135°, delta = -55° and   
         alpha = 105°, delta = -25° (beta<20° N).   
        
     Figure 4: Radiant position of the pi-Puppids   
        
     [image:55]   
        
     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 was due   
     at perihelion on 1997 August 30, but in 1997 an almost full Moon coincided   
     with the shower's peak. At the 1998 return, we reach the closest-approach   
     point to the orbit almost eight months after the comet, so this will be a   
     useful year to check for pi-Puppid activity further from the comet,   
     especially as the Moon is just three days from new for the maximum.   
        
     The shower is best-seen from the southern hemisphere, with useful   
     observations mainly possible before local midnight, as the radiant is very   
     low or setting after 1h local time. 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 either.   
     


July to September

   
     Minor shower activity continues apace from near-ecliptic sources throughout   
     this quarter, first from the Sagittarids, then the Aquarid and Capricornid   
     showers (discussed below with the Piscis Austrinids; the Southern iota-   
     Aquarid and Northern delta-Aquarid maxima lose out to August's full Moon),   
     and finally the Piscids into September. Other showers that vanish into   
     bright moonlight this quarter include the Pegasids and Phoenicids in July;   
     the Perseids in August (coverage is still important, but will be   
     exceptionally difficult with a waning gibbous Moon; the maxima are   
     predicted for August 12, 14h UT and August 12, 22h UT); and the alpha- and   
     delta-Aurigids in September (alpha-Aurigid peak due around September 1, 05h   
     UT). At least the minor kappa-Cygnids still survive this moonlight   
     onslaught! For daylight radio observations, the interest of May-June has   
     waned, but there remain the visually-inaccessible gamma-Leonids (peak due   
     August 25d 14h UT), and a tricky visual shower, the Sextantids (maximum   
     expected September 27d 14h UT). The latter has no problems from the waxing   
     crescent Moon, but its radiant will rise less than an hour before dawn   
     ineither hemisphere.   
        
     


Piscis Austrinids and Aquarid/Capricornid Complex

   
     


Piscis Austrinids

   
     Active  : July 15-August 10;   
     Maximum  : July 28 (lambda = 125°);   
     ZHR   = 5;   
     Radiant  : alpha = 341°, delta = -30°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     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).   
        
     Figure 5: Radiant position of the Piscis Austrinids   
        
     [image:669]   
        
     


Southern delta-Aquarids

   
     Active  : July 12-August 19; Maximum: July 28, 06h UT (lambda = 125°);   
     ZHR   = 20;   
     Radiant  : alpha = 339°, delta = -16°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     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).   
        
     Figure 6: Radiant position of the Southern and Northern delta-Aquarids   
        
     [image:668]   
        
     


alpha-Capricornids

   
     Active  : July 3-August 15;   
     Maximum  : July 30 (lambda = 127°);   
     ZHR   = 4;   
     Radiant  : alpha = 307°, delta = -10°;   
     Radiant drift: see Table 3;   
     Radius  : 8°;   
     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.)   
        
     Figure 7: Radiant position of the Alpha Capricornids   
        
     [image:668]   
        
     


Northern iota-Aquarids

   
     Active  : August 11-31;   
     Maximum  : August 20 (lambda = 147°);   
     ZHR   = 3;   
     Radiant  : alpha = 327°, delta = -6°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     V   = 31 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).   
        
     Figure 8: Radiant position of the Southern and Northern iota-Aquarids   
        
     [image:669]   
        
     The Aquarids and Piscis Austrinids are all 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 around 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.   
        
     All the above listed shower maxima are almost free from lunar interference   
     in 1998. The Piscis Austrinid, Southern delta-Aquarid and alpha-Capricornid   
     maxima have only a waxing crescent Moon to contend with, while August's new   
     Moon falls favourably for the Northern iota-Aquarid peak. All these   
     radiants are above the horizon for much of the night.   
        
     


kappa-Cygnids

   
     Active  : August 3-25;   
     Maximum  : August 18, (lambda = 145°);   
     ZHR   = 3;   
     Radiant  : alpha = 286°, delta= +59°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     V   = 25 km/s;   
     r   = 3.0;   
     TFC   : alpha = 330°, delta = +60° and   
         alpha = 300°, delta = +30° (beta> 20° N).   
        
     The waning crescent Moon will rise during the local early morning hours at   
     the kappa-Cygnid peak this year, a very minor nuisance only for watchers   
     north of the equator, where the shower is chiefly accessible from. Its r-   
     value suggests telescopic and video observers may benefit from its   
     presence, but visual and photographic workers should note that occasional   
     slow fireballs from this source have been reported too. Its almost   
     stationary radiant results from its close proximity to the ecliptic north   
     pole in Draco. There has been some suggestion of a variation in its   
     activity at times, perhaps coupled with a periodicity in fireball   
     sightings, but more data are urgently needed on a shower that often is   
     ignored in favour of the Perseids during August.   
        
     


Piscids

   
     Active  : September 1-30;   
     Maximum  : September 20, (lambda = 177°);   
     ZHR   = 3;   
     Radiant  : alpha = 5°, delta= -1°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     V   = 26 km/s;   
     r   = 3.0;   
     TFC   : alpha = 340° to 20°, delta = -15° to +15°,   
         choose pairs separated by about 30° in alpha (beta any).   
        
     Figure 9: Radiant position of the Piscids   
        
     [image:64]   
        
     The Piscids are a poorly-studied minor shower, with a radiant very close to   
     the March equinox point in the sky. Consequently, they can be studied   
     equally well from either hemisphere throughout the night near the September   
     equinox, close to their probable maximum time. This year, new Moon falls   
     exactly on September 20, but there is some doubt as to exactly when the   
     Piscid peak may occur - or indeed, if there is only the one. Telescopic and   
     video methods can be usefully employed to study it, along with careful   
     visual plotting.   
     

October to December

Ecliptical minor shower activity reaches what might be regarded as a peak in early to mid November, with the Taurid streams in action (the Southern Taurid maximum will be lost to bright moonlight this year, but something of the Northern peak should still be seen). Before then come an important return of the Draconids, the Orionid and the minor epsilon-Geminid maxima. This is also a key year for the Leonids in November, and a good one to check for a repeat of 1995's outburst for the alpha-Monocerotids. December's full Moon claims the maxima of the chi-Orionids, Phoenicids (December 6, 13h UT) and the early, better, part of the weak Puppid-Velid complex, as well as much of the Monocerotids and sigma-Hydrids. This does mean the Geminids, Coma Berenicids and Ursids are all much better-placed with regard to the Moon.


Draconids

   
     Active  : October 6-10;   
     Maximum  : October 8, 17-23h, (lambda = 159.40°),   
     ZHR   = periodic, up to storm levels;   
     Radiant  : alpha = 262°, delta = +54°;   
     Radiant drift: negligible;   
     Radius  : 5°;   
     V   = 20 km/s;   
     r   = 2.6;   
     TFC   : alpha = 290°, delta = +65° and   
         alpha = 288°, delta = +39° (beta>30° N).   
        
     Despite the presence of a waning gibbous Moon, which will rise within 2-3   
     hours of nightfall for the northern hemisphere sites this shower is visible   
     from, 1998 is a very important year for observing the Draconids. 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 around 20-200+), most recently in 1985. So far, detectable   
     activity has only been seen in years when the stream's parent comet,   
     21P/Giacobini-Zinner, has returned to perihelion, which it is expected to   
     do again in 1998 November. Perturbations of the stream, coupled with the   
     fact that the 1946 event remains the best-observed return, mean predicting   
     when activity might occur is very difficult. The spread in solar longitudes   
     at which notable past activity has been detected is from lambda = 195.26°   
     (1985) to lambda = 197.0° (1933), which equates to times between October   
     8, 17h UT and October 10, 12h UT in 1998. This is certainly a period that   
     all observers should be alert to, using a full range of techniques, but   
     with the Earth expected to pass the comet's node at lambda = 195.398°   
     (October 8, 21 h UT), times earlier in this period may be more likely. The   
     peak time given in the box above is a mean value of the previous returns,   
     and should be viewed more as a general guide than an absolute value. The   
     radiant, near Draco's "Head", is circumpolar from many locations, but is   
     higher in the pre-midnight and near-dawn hours on October 8-10.   
     Photographic and video data would be especially valuable in case high rates   
     do take place.   
        
     


epsilon-Geminids

   
     Active  : October 14-27;   
     Maximum  : October 18, (lambda = 205°),   
     ZHR   = 2;   
     Radiant  : alpha = 102°, delta = +27°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     V   = 70 km/s;   
     r   = 3.0;   
     TFC   : alpha = 90°, delta = +20° and   
         alpha = 125°, delta = +20° (beta>20° S).   
        
     A weak minor shower, whose meteors are very like the Orionids, active, and   
     at maximum, around the same time, so great care must be taken to separate   
     the two sources by instrumental techniques - especially video or telescopic   
     work - or visual plotting. New Moon on October 20 presents an excellent   
     opportunity to obtain more data on them from either hemisphere, although   
     northern observers have an advantage. The radiant is higher only after   
     midnight.   
        
     


Orionids

   
     Active  : October 2 - November 7;   
     Maximum  : October 21, (lambda = 208°),   
     ZHR   = 20;   
     Radiant  : alpha = 95°, delta = +16°;   
     Radiant drift: see Table 3;   
     Radius  : 10°;   
     V   = 66 km/s;   
     r   = 2.9;   
     TFC   : alpha = 100°, delta = +39° and   
         alpha = 75°, delta = +24° (beta>40° N); or   
         alpha = 80°, delta = +1° and   
         alpha = 117°, delta = +1° (beta<40° N).   
        
     Figure 10: Radiant position of the Orionids and epsilon-Geminids   
        
     [image:66]   
        
     October's new Moon enhances the Orionids this year too. They are noted for   
     having several maxima other than the main one detailed above, with activity   
     sometimes remaining almost constant for several consecutive nights centred   
     on this peak. In 1993, 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. 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 almost on 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.   
        
     


Leonids

   
     Active  : November 14-21;   
     Maximum  : November 17, 19h UT (lambda = 235.25°),   
     ZHR   = 40+ (45 in 1996), but may reach storm levels in 1998-99;   
     Radiant  : alpha = 153°, delta = +22°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     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>40° N);   
        and after 04h local time alpha = 160°, delta = 0° (beta>40° N);   
         before 00h local time alpha = 120°, delta = +10° (beta>0° N)   
        and alpha = 160°, delta = -10° (beta<0° N).   
        
     Figure 11: Radiant position of the Leonids   
        
     [image:68]   
        
     The recovery of the Leonids' parent comet, 55P/Tempel-Tuttle, on 1997 March   
     4 has raised hopes further that a storm of Leonids might occur in 1998 or   
     1999. 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! Visual IMO International Leonid Watch and   
     radio observations in 1996 indicated quite a broad Leonid maximum between   
     lambda = around 235.1°-235.4° (equivalent to 1998 November 17, 14h-22h   
     UT), with one minor peak at lambda = 235.17° (1998 November 17, 17h UT).   
     As the Earth should pass the node of the comet's orbit around 1998   
     November 17, 19h UT (lambda = around 235.3°), this may well be the most   
     likely time for the very highest activity to occur.   
        
     As the radiant, in Leo's "Head" or "Sickle" asterism, rises only around   
     local midnight (or indeed afterwards south of the equator), places in the   
     Far East, including China, Eastern Siberia and Japan, south through the   
     Western Pacific islands to Australia, should be the favoured spots, if the   
     maximum keeps to this time. Even a minor variation could mean places east   
     or west of this zone may see something of the shower's best too, however.   
     Look out for further updates in the IMO's journal WGN after the 1997   
     return. The Moon is just two days from new on November 17, so it will cause   
     no problems this year, and all observing methods should be utilised to the   
     full, especially photography and video if a storm manifests.   
        
     


alpha-Monocerotids

   
     Active  : November 15-25;   
     Maximum  : November 21, 20h 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 3;   
     Radius  : 5°;   
     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);   
        
     Another late-year shower capable of producing surprises, the alpha-   
     Monocerotids gave their most recent brief outburst in 1995 (the top EZHR,   
     around 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   
     propsed 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. New Moon on November 19 makes this an excellent year for   
     such scrutiny, with the radiant well on view in both hemispheres after   
     about 23h local time or so.   
        
     


Geminids

   
     Active  : December 7-17;   
     Maximum  : December 14, 05h UT (lambda = 262.0°),   
     ZHR   = 120;   
     Radiant  : alpha = 112°, delta = +33°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     V   = 35 km/s;   
     r   = 2.6;   
     TFC   : before 23h local time alpha = 87°, delta = +20° and   
         alpha = 135°, delta = +49°;   
         after 23h local time alpha = 87°, delta = +20° and   
         alpha = 129°, delta = +20° (beta>40° N);   
         alpha = 120°, delta = -3° and   
         alpha = 84°, delta = +10° (beta<20° N);   
     PFC   : alpha = 150°, delta = +20° and   
         alpha = 60°, delta = +40° (beta>20° N);   
        and alpha = 135°, delta = -5° and   
         alpha = 80°, delta = 0° (beta<20° N)   
        
     Figure 12: Radiant position of the Geminids   
        
     [image:72]   
        
     One of the finest annual showers presently observable, their early stages   
     will be lost to moonlight this year, but their peak occurs with a waning   
     crescent Moon which should present few problems, and then only late in the   
     night. Well north of the equator, the radiant rises around sunset, and can   
     be usefully observed from the local evening hours onwards, but in the   
     southern hemisphere, the radiant appears only around local midnight or so.   
     Even here, this is a splendid stream of often bright, medium-speed meteors,   
     a rewarding sight for all watchers. The peak has shown slight signs of   
     variability in its maximum rates and the actual peak timing (ZHRs were   
     around 110 around lambda 262.2°-262.4° in 1996, for instance), so the   
     best activity may occur a little before or after the suggested time above.   
     Even so, European, African, Near Eastern and American sites are the most   
     likely beneficiaries of the very best Geminid rates in 1998. Some mass-   
     sorting within the stream means the fainter telescopic meteors should be   
     most abundant almost 1° of solar longitude ahead of the visual maximum,   
     with telescopic results indicating these meteors radiate from an elongated   
     region, perhaps with three sub-centers. Further results on this topic would   
     be useful, but all observing methods can be employed to observe the shower.   
        
     


Coma Berenicids

   
     Active  : December 12 - January 23;   
     Maximum  : December 20, (lambda = 268°),   
     ZHR   = 5;   
     Radiant  : alpha = 175°, delta = +25°;   
     Radiant drift: see Table 3;   
     Radius  : 5°;   
     V   = 65 km/s;   
     r   = 3.0;   
     TFC   : alpha = 180°, delta = +50° and   
         alpha = 165°, delta = +20° before 03h local time; or   
         alpha = 195°, delta = +10° and   
         alpha = 200°, delta = +45° after 03h local time (beta>20° N).   
        
     Figure 13: Radiant position of the Coma Berenicids   
        
     [image:73]   
        
     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 is just two days after new Moon. The radiant is at a useful elevation   
     from local midnight onwards.   
        
     


Ursids

   
     Active  : December 17-26;   
     Maximum  : December 22, 18h UT (lambda = 270.7°);   
     ZHR   = 10 (occasionally variable up to 50);   
     Radiant  : alpha = 217°, delta = +76°;   
     Radiant drift: see Table 3;   
     radius  : 5°;   
     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 14: Radiant position of the Ursids   
        
     [image:672]   
        
     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, 20h 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 waxing crescent Moon will give dark skies for observations almost all   
     night on December 22.   
        
     


Abbreviations

   
     alpha, delta: Coordinates for a shower's radiant position, usually at   
     maximum; is right ascension, 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 3 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 a 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   
     elevation of the radiant. Note that the TFCs are also useful centres to use   
     for video camera fields as well.   
        
        
     


Tables

   
     Table 1: Lunar phases for 1998.   
        
     New   First   Full   Last   
     Moon   Quarter  Moon   Quarter   
        January 5  January 12  January 20   
     January 28 February 3  February 11 February 19   
     February 26 March 5  March 13  March 21   
     March 28  April 3  April 11  April 19   
     April 26  May 3   May 11   May 19   
     May 25  June 2   June 10  June 17   
     June 24  July 1   July 9   July 16   
     July 23  July 31  August 8  August 14   
     August 22  August 30  September 6 September 13   
     September 20 September 28 October 5  October 12   
     October 20 October 28  November 4  November 11   
     November 19 November 27 December 3  December 10   
     December 18 December 26   
        
     
Table 2: Working list of visual meteor showers. Details in this Table correct according to the best information available in June 1997. Contact the IMO's Visual Commission for more information. Maximum dates in parentheses indicate reference dates for the radiant, not true maxima. Some showers have ZHRs that vary from year to year. The most recent reliable figure is given here, except for possibly periodic showers that are noted as "var." = variable. Shower Activity Maximum Radiant Period Date lambda alpha delta ° ° ° Quadrantids Jan 01-Jan 05 Jan 03 283.16 230 +49 delta-Cancrids Jan 01-Jan 24 Jan 17 297 130 +20 alpha-Centaurids Jan 28-Feb 21 Feb 07 318.7 210 -59 delta-Leonids Feb 15-Mar 10 Feb 24 336 168 +16 gamma-Normids Feb 25-Mar 22 Mar 13 353 249 -51 Virginids Jan 25-Apr 15 (Mar 24)(004) 195 -04 Lyrids Apr 16-Apr 25 Apr 22 032.1 271 +34 pi-Puppids Apr 15-Apr 28 Apr 23 033.5 110 -45 eta-Aquarids Apr 19-May 28 May 05 045.5 338 -01 Sagittarids Apr 15-Jul 15 (May 20)(059) 247 -22 Pegasids Jul 07-Jul 13 Jul 10 108 340 +15 July Phoenicids Jul 10-Jul 16 Jul 13 111 032 -48 Pisces Austrinids Jul 15-Aug 10 Jul 28 125 341 -30 Southern delta-Aquarids Jul 12-Aug 19 Jul 28 125 339 -16 alpha-Capricornids Jul 03-Aug 15 Jul 30 127 307 -10 Southern iota-Aquarids Jul 25-Aug 15 Aug 04 132 334 -15 Northern delta-Aquarids Jul 15-Aug 25 Aug 08 136 335 -05 Perseids Jul 17-Aug 24 Aug 12 140.0 046 +58 kappa-Cygnids Aug 03-Aug 25 Aug 18 145 286 +59 Northern iota-Aquarids Aug 11-Aug 31 Aug 20 147 327 -06 alpha-Aurigids Aug 25-Sep 05 Sep 01 158.6 084 +42 delta-Aurigids Sep 05-Oct 10 Sep 08 166 060 +47 Piscids Sep 01-Sep 30 Sep 20 177 005 -01 Draconids Oct 06-Oct 10 Oct 08 195.4 262 +54 epsilon-Geminids Oct 14-Oct 27 Oct 18 205 102 +27 Orionids Oct 02-Nov 07 Oct 21 208 095 +16 Southern Taurids Oct 01-Nov 25 Nov 05 223 052 +13 Northern Taurids Oct 01-Nov 25 Nov 12 230 058 +22 Leonids Nov 14-Nov 21 Nov 17 235.25 153 +22 alpha-Monocerotids Nov 15-Nov 25 Nov 21 239.32 117 +01 chi-Orionids Nov 26-Dec 15 Dec 02 250 082 +23 Phoenicids Nov 28-Dec 09 Dec 06 254.25 018 -53 Puppid-Velids Dec 01-Dec 15 (Dec 07)(255) 123 -45 Monocerotids (Dec) Nov 27-Dec 17 Dec 09 257 100 +08 sigma-Hydrids Dec 03-Dec 15 Dec 12 260 127 +02 Geminids Dec 07-Dec 17 Dec 14 262.0 112 +33 Coma Berenicids Dec 12-Jan 23 Dec 20 268 175 +25 Ursids Dec 17-Dec 26 Dec 22 270.7 217 +76
Shower v r ZHR IMO km/s Code Quadrantids 41 2.1 120 QUA delta-Cancrids 28 3.0 4 DCA alpha-Centaurids 56 2.0 6 ACE delta-Leonids 23 3.0 2 DLE gamma-Normids 56 2.4 8 GNO Virginids 30 3.0 5 VIR Lyrids 49 2.9 15 LYR pi-Puppids 18 2.0 var. PPU eta-Aquarids 66 2.7 60 ETA Sagittarids 30 2.5 5 SAG Pegasids 70 3.0 3 JPE July Phoenicids 47 3.0 var. PHE Pisces Austrinids 35 3.2 5 PAU Southern delta-Aquarids 41 3.2 20 SDA alpha-Capricornids 23 2.5 4 CAP Southern iota-Aquarids 34 2.9 2 SIA Northern delta-Aquarids 42 3.4 4 NDA Perseids 59 2.6 90 PER kappa-Cygnids 25 3.0 3 KCG Northern iota-Aquarids 31 3.2 3 NIA alpha-Aurigids 66 2.5 10 AUR delta-Aurigids 64 3.0 6 DAU Piscids 26 3.0 3 SPI Draconids 20 2.6 var. GIA epsilon-Geminids 70 3.0 2 EGE Orionids 66 2.9 20 ORI Southern Taurids 27 2.3 5 STA Northern Taurids 29 2.3 5 NTA Leonids 71 2.5 40+ LEO alpha-Monocerotids 65 2.4 var. AMO chi-Orionids 28 3.0 3 XOR Phoenicids 18 2.8 var. PHO Puppid-Velids 40 2.9 10 PUP Monocerotids (Dec) 42 3.0 3 MON sigma-Hydrids 58 3.0 2 HYD Geminids 35 2.6 120 GEM Coma Berenicids 65 3.0 5 COM Ursids 33 3.0 10 URS
Table 3: Radiant positions during the year in alpha and delta. COM DCA Jan 0 186 +20 112 +22 QUA 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 Jun 25 280 -23 Jun 30 284 -23 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
Table 4: Working list of daytime radio meteor streams. The "Best Observed" columns give the approximate local mean times between which a four-element antenna at an elevation of 45° receiving a signal from a 30-kW transmitter 1000 km away should record at least 85% of any suitably positioned radio- reflecting meteor trails for the appropriate latitudes. Note that this is often heavily dependent on the compass direction in which the antenna is pointing, however, and applies only to dates near the shower's maximum. 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


Useful addresses

   
     For more information on observing techniques, and when submitting results,   
     please contact the appropriate IMO Commission Director:   
        
     Fireball Data Center : André Knöfel, Saarbrückerstraße 8,   
     (FIDAC)     D-40476 Düsseldorf, Germany.   
           (e-mail: fidac@imo.net)   
        
     Photographic Commission: Marc de Lignie, Prins Hendrikplein 42,   
           NL-2264 SN Leidschendam, the Netherlands.   
           (e-mail: photo@imo.net)   
        
     Radio Commission:   Temporarily vacant   
           (e-mail: radio@imo.net)   
        
     Telescopic Commission: Malcolm Currie, 25 Collett Way, Grove, Wantage,   
           Oxon. OX12 0NT, UK.   
           (e-mail: tele@imo.net)   
        
     Visual Commission:  Rainer Arlt, Berliner Straße 41, D - 14467 Potsdam,   
           Germany   
           (e-mail: visual@imo.net)   
        
     or contact IMO's Homepage in the World-Wide-Web:   
        
     http://www.imo.net/   
        
     For further details on IMO membership, please write to:   
           Ina Rendtel, IMO Treasurer, Gontardstraße 11   
           D-14471 Potsdam, Germany.   
           (e-mail: treasurer@imo.net)   
        
     Please try to enclose return postage when writing to any IMO officials,   
     either in the form of stamps (same country only) or as an International   
     Reply Coupon (I.R.C.--available from main postal outlets). Thank you!