IMO Meteor Shower Calendar 2011

Compiled by Alastair McBeath. Based on information in “Handbook for Meteor Observers”, edited
by Jürgen Rendtel and Rainer Arlt, IMO, 2009 (referred to as ‘HMO’ in the Calendar), and “A
Comprehensive List of Meteor Showers Obtained from 10 Years of Observations with the IMO Video
Meteor Network” by Sirko Molau and Jürgen Rendtel (WGN 37:4, 2009, pp. 98–121; referred to as
‘VID’ in the Calendar), as amended by subsequent discussions and additional material extracted from
reliable data analyses produced since. Particular thanks are due to Rainer Arlt, Jeff Brower, David
Entwistle, Esko Lyytinen, Jürgen Rendtel and Jérémie Vaubaillon for new
information and comments in respect of events in 2011.

Introduction

Welcome to the twenty-first International Meteor Organization (IMO) Meteor Shower Calendar, for
2011. The year starts brightly enough meteorically, with the Quadrantid peak perfectly-timed for new
Moon, followed by favourable returns for the α–Centaurids and η–Aquariids, but the
later-year major showers are all quite to very badly moonlit. The Draconids may yield some activity
in October, sadly close to full Moon too, and the almost-unknown ε–Eridanids could produce
equally moonlit rates in September. There are changes to some of the less active sources based on
the latest IMO video analyses, including for the near-Auriga showers of September-October, and for
the Southern Taurids especially. There are always other minor showers to be monitored of course, and
ideally, meteor observing should be carried on throughout the year to check on all the established
sources, and for any new ones. Such routine monitoring is possible now with automated video systems
especially, but we appreciate not everyone is able to employ these, and that observing in other ways
regularly is impractical for most people, so the Shower Calendar has been helping to highlight times
when a particular effort might be most usefully employed since 1991.

The heart of the Calendar is the Working List of Visual Meteor Showers, Table 5, which has been undergoing a thorough revision in the last
few years, a process that is still underway, in order to help it remain the single most accurate
listing available anywhere today for naked-eye meteor observing. Of course, for all its accuracy, it
is a Working List, so is continually subject to further checks and corrections, based on the best
data we had at the time the Calendar was written, thus it is always as well to check the information
here fully, taking account of any later changes noted in the IMO’s journal WGN or on the IMO
website, before going out to observe (and please notify us if you find any anomalies!).

This is a particularly dynamic time for minor shower studies, with video results detecting many
weak showers too minor to be visually-observed, as well as sometimes revealing fresh aspects of
those already known, and even of the low-activity phases of some of the major showers well away from
their maxima. Video has established itself as a valuable tool in meteor studies in recent years, and
professional radar meteor examinations have been producing excellent new results as well, but we
should not forget the other instrumental techniques available to amateur observers. Telescopic
observations can also separate minor shower activity from the omnipresent background sporadics, and
detect showers whose meteors are too faint even for current video systems. Still-imaging enables a
whole range of studies to be carried out on the brighter meteors particularly, and multi-station
observing with still or video cameras can allow orbital data to be established, essential for
meteoroid-stream examinations. Showers with radiants too near the Sun for observing by the various
optical methods can be detected by forward-scatter radio or radar observations. Some of these
showers are given in Table 7, the Working List of Daytime Radio
Meteor Streams. Automated radio and radar work also allows 24-hour coverage of meteor activity.

The IMO’s aims are to encourage, collect, analyze, and publish combined meteor data obtained from
sites all over the globe, to help better our understanding of the meteor activity detectable from
the Earth’s surface. Thus, we encourage these more specialist forms of observing alongside visual
work. Consequently, for best effects, all meteor workers, wherever you are and whatever methods you
use to record meteors, should follow the standard IMO observing guidelines when compiling your
information, and submit those data promptly to the appropriate Commission for analysis (contact
details are at the end of the Calendar). Thanks to the efforts of the many IMO observers worldwide
since 1988 that have done this, we have been able to achieve as much as we have to date, including
keeping the shower listings vibrant. This is not a matter for complacency however, since it is
solely by the continued support of many people across the planet that our steps towards constructing
a better and more complete picture of the near-Earth meteoroid flux can proceed.

Although timing predictions are included below on all the more active night-time and daytime
shower maxima, as reliably as possible, it is essential to understand 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 regular attention until quite
recently). In addition, variations in individual showers from year to year mean past returns are
only a guide as to when even major shower peaks can be expected. As noted already, the information
given here may be updated and added-to after the Calendar has been published. Some showers are known
to show particle mass-sorting within their meteoroid streams, so the radar, radio, still-imaging,
telescopic, video and visual meteor maxima may occur at different times from one another, and not
necessarily just in those showers. The majority of data available are for visual shower maxima, so
this must be borne in mind when employing other observing techniques.

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!

Antihelion Source

The Antihelion Source (ANT) is a large, roughly oval area around α = 30° by δ =
15° in size, centred about 12° east of the solar opposition point on the ecliptic, hence its
name. It is not a true shower at all, but is rather a region of sky in which a number of variably,
if weakly, active minor showers have their radiants. Until 2006, attempts were made to define
specific showers within this complex, but this often proved very difficult for visual observers to
achieve. IMO video results from the last decade have shown why, because even instrumentally, it was
impossible to define distinct radiants for many of the showers here! Thus we believe currently it is
best for observers to simply identify meteors from these streams as coming from the ANT alone. At
present, we think the July-August α–Capricornids (CAP), and particularly the δ–Aquariids
(SDA), should remain discretely-observable visually from the ANT, so they have been retained on the
Working List, but time and plenty of observations will tell, as ever. Later in the year, the
strength of the Taurid showers (STA and NTA) means the ANT should be considered inactive while the
Taurids are underway, from early September to early December (note this interval has been extended
since the 2010 Shower Calendar). To assist observers, a set of charts showing the location for the
ANT and any other nearby shower radiants is included here, to complement the numerical positions of
Table 6, while comments on the ANT’s location and likely
activity are given in the quarterly summary notes.

January to March

New Moon falls perfectly for the northern-hemisphere Quadrantid maximum, and moonlight
circumstances also favour the southern-hemisphere’s α–Centaurid and minor γ–Normid
returns. The ANT’s radiant centre starts January in south-east Gemini, and crosses Cancer during
much of the month, before passing into southern Leo for most of February. It then slips through
southern Virgo during March. Likely ANT ZHRs will be < 2, though IMO analyses suggest there may
be an ill-defined minor peak with ZHRs ∼ 2 to 3 around λ⊙ ∼ 286°–293° (January 6 to
13 in 2011, much of which has only a waxing crescent Moon, if so), and ZHRs could be ∼ 3 for most of
March. The late January to early February spell, during which several new, swift-meteor, minor
showers, radiating from the Coma-Leo-Virgo area have been proposed in some recent years, is spoilt
by the full to waning Moon for its potential core period, January 20–27. Theoretical approximate
timings (rounded to the nearest hour) for the daytime radio shower maxima this quarter are:
Capricornids/Sagittariids – February 1, 21h UT; and χ–Capricornids – February 13, 22h UT. Recent
radio results have implied the Cap/Sgr maximum may variably fall sometime between February 1–4
however, while activity near the expected χ–Capricornid peak has tended to be slight and up to a
day late. Both showers have radiants < 10°–15° west of the Sun at maximum, so cannot be
regarded as visual targets even from the southern hemisphere.

Quadrantids (QUA)

Active: December 28 – January 12; Maximum: January 4, 01h10m UT (λ⊙ = 283.16°); ZHR = 120 (can vary ∼ 60–200); Radiant: α = 230°, δ = +49°; Radiant drift: see Table 6; V∞ = 41 km/s; r = 2.1 at maximum, but variable; TFC: α = 242°, δ = +75° and α = 198°, δ = +40° (β > 40° N). IFC: before 0h local time α = 150°, δ = +70°; after 0h local time α = 180°, δ = +40° and α = 240°, δ = +70° (β > 40° N).

New Moon just eight hours after the predicted Quadrantid maximum creates ideal circumstances for
observing the shower from northern hemisphere sites this year. From many such places, the shower’s
radiant is circumpolar, in northern Boötes, attaining a useful elevation only after local
midnight, and rising higher in the sky towards morning twilight. This means places at European
longitudes east to those of central Asia should be best-placed to record what happens.

However, computations by Jérémie Vaubaillon have suggested the peak could happen at
a somewhat different time between roughly 21h UT on January 3 to 06h UT on January 4 (see the
diagram on HMO p. 129). The occasional long-pathed shower meteor might be seen from southern
hemisphere sites around dawn, but sensible Quadrantid watching cannot be carried out from such
places.

The maximum timing above is based on the best-observed return of the shower ever analysed, from
IMO 1992 data, confirmed by radio results in most years since 1996. 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 2009 persisted for almost fourteen hours at close
to their best, with the predicted maximum time falling around an hour or two after the mid-point of
this extended interval. An added level of complexity comes from the fact 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. A few, but apparently not all, years since 2000 seem to have produced a,
primarily radio, maximum following the main visual one by some 9–12 hours. Visual confirmation of
any repeat of such activity would be welcomed.

VID data recently indicated the QUA may be active weakly for longer than previous visual
estimates had inferred, perhaps from December 28 to January 12, compared to just January 1–10
visually (HMO). It is not certain visual observers will be able to follow the shower for so long as
yet, as the early and late activity may be too low to be separated from the visual sporadic
background. Past observations have suggested the QUA radiant is diffuse away from the maximum too,
contracting notably during the peak itself, although this may be a result of the very low activity
outside the hours near maximum. Still-imaging and video observations would be particularly welcomed
by those investigating this topic, using the IFCs and TFCs given above, along with telescopic
results.

α–Centaurids (ACE)

Active: January 28 – February 21; Maximum: February 8, 11h30m UT (λ⊙ = 319.2°); ZHR = variable, usually ∼ 6, but may reach 25+; Radiant: α = 210°, δ = −59°; Radiant drift: see Table 6; V∞ = 56 km/s; r = 2.0.

In theory, the α–Centaurids are one of the main southern summer high points, from past
records supposedly producing many very bright, even fireball-class, objects (meteors of at least
magnitude −3), commonly with fine persistent trains. However, the average peak ZHR between 1988–2007
was merely 6 (HMO, p. 130), albeit coverage has frequently been extremely patchy. Despite this, in
1974 and 1980, bursts of only a few hours’ duration apparently yielded ZHRs closer to 20–30.

As with many southern hemisphere sources, we have more questions than answers at present, nor do
we have any means of telling when, or if, another stronger event might happen. Consequently, imaging
and visual observers are urged to be alert at every opportunity. The radiant is nearly circumpolar
for much of the sub-equatorial inhabited Earth, and is at a useful elevation from late evening
onwards. The Moon is merely a waxing crescent on February 8, and will have set by mid-evening from
mid-southerly sites.

γ–Normids (GNO)

Active: February 25 – March 22; Maximum: March 15 (λ⊙ = 354°); ZHR = 6; Radiant: α = 239°, δ = −50°, Radiant drift: see Table 6; V∞ = 56 km/s; r = 2.4; TFC: α = 225°, δ = −26° and α = 215°, δ = −45° (β < 15° S).

For most of their activity, γ–Normid ZHRs seem to be virtually undetectable above the
background sporadic rate. The maximum itself has been reported as quite sharp, and an analysis of
IMO data from 1988–2007 showed an average peak ZHR of ∼ 6 at λ⊙ = 354°, with ZHRs < 3
visible on all other dates during the shower (HMO, pp. 131–132). Limited data means this is
uncertain, and activity may vary somewhat at times, with occasional broader, or less obvious, maxima
having been noted in the past. Results since 1999 have suggested the possibility of a short-lived
peak alternatively between λ⊙ ∼ 347°–357°, equivalent to 2011 March 8–18, while video
and visual plotting information from the same period agreed on the above radiant position, though
this was different to that suggested earlier for the shower. Post-midnight watching yields better
results, when the radiant is rising to a reasonable elevation from southern hemisphere sites (the
radiant does not rise for many northern ones). The shower badly needs more regular attention, and
March’s waxing Moon, at first quarter on March 12, means 2011 would be a good year to start, as
moonset leaves at least some dark-sky observing time after midnight for virtually the whole
potentially extended peak spell. All observing techniques can be employed.

April to June

Meteor activity picks up towards the April-May boundary, though neither of the two shower maxima
in late April are observably Moon-free. The Lyrids should peak between about 15h30m UT on April 22
to 02h30m UT on April 23 (and will probably give better rates the closer the maximum falls to 23h UT
on the 22nd), while the π–Puppid maximum is due around 04h UT on April 24. Something of the
usually-minor π–Puppids may still be visible before moonrise, however, as they are best-seen
before local midnight from the southern hemisphere. No unusual activity has been predicted from them
for this year. The η–Aquariids in early May are much better-placed, with some dark-sky observing
possible for the minor η–Lyrids a few days afterwards as well. Later in May and throughout June,
most of the meteor action switches to the daytime sky, with six shower maxima expected during this
time. Although occasional meteors from the ο–Cetids and Arietids have been claimed as seen
from tropical and southern hemisphere sites visually in past years, ZHRs cannot be sensibly
calculated from such observations. For radio observers, the theoretical UT peaks for these showers
are as follows: April Piscids – April 20, 22h; δ–Piscids – April 24, 22h; ε–Arietids –
May 9, 22h; May Arietids – May 16, 21h; ο–Cetids – May 20, 20h; Arietids – June 7, 23h;
ζ–Perseids – June 9, 23h; β–Taurids – June 28, 22h. Signs of most were found in radio data
from 1994–2007, though some are difficult to define individually because of their proximity to other
radiants. There seems to be a modest recurring peak around April 24, perhaps due to combined rates
from the first three showers listed here, for instance, while the Arietid and ζ–Perseid maxima
tend to blend into one another, producing a strong radio signature for several days in early to mid
June. There are indications these two June shower maxima now each occur up to a day later than
indicated above.

The ANT should be relatively strong, with ZHRs of 3 to 4 found in recent investigations through
till mid April, and again around late April to early May, late May to early June, and late June to
early July. At other times, the ZHR seems to be below ∼ 2 to 3. The radiant area drifts from
south-east Virgo through Libra in April, then across the northern part of Scorpius to southern
Ophiuchus in May, and on into Sagittarius for much of June.

For northern observers, circumstances for checking on any potential June Lyrids are very poor
this year around their theoretical peak on June 16 (the shower is not currently given on the Working
List, as it has not been found in recent investigations), but will have improved for possible June
Boötid hunting later in June.

η–Aquariids (ETA)

Active: April 19 – May 28; Maximum: May 6, 13h UT (λ⊙ = 45.5°); ZHR = 70 (periodically variable, ∼ 40–85); Radiant: α = 338°, δ = −01°; Radiant drift: see Table 6; V∞ = 66 km/s; r = 2.4; TFC: α = 319°, δ = +10° and α = 321°, δ = −23° (β < 20° S).

A fine, rich stream associated with Comet 1P/Halley, like the Orionids of October, but one
visible for only a few hours before dawn, essentially from tropical and southern hemisphere sites.
Some useful results have come even from places 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, η–Aquariids tend to have very long paths, which can mean observers
underestimate the angular speeds of the meteors, so extra care is needed when making such
reports.

A relatively broad maximum, sometimes with a variable number of submaxima, usually occurs in
early May. Fresh IMO analyses in recent years, based on data collected between 1984–2001, have shown
that ZHRs are generally above 30 between about May 3–10, and that the peak rates appear to be
variable on a roughly 12-year timescale. The most recent highest rates should have happened around
2008–2010, if this Jupiter-influenced cycle was borne-out, so ZHRs should be falling back from this
peak in 2011, according to this idea.

Although activity in 2007 seemed unexpectedly weaker than normal (peak ZHRs maybe only ∼ 50),
rates seemed to have been much better in 2008 and 2009 (ZHRs of ∼ 85 and 65 respectively). There
seemed to have been no additional influence following the protracted, sometimes stronger than
expected, Orionid returns from October 2006–2009 inclusive in the η–Aquariids in those years, as
far as the available results allowed. New Moon on May 3 creates perfect viewing conditions for
whatever the shower provides in 2011. All forms of observing can be used to study it, with radio
work allowing activity to be followed even from many northern latitude sites throughout the daylight
morning hours. The radiant culminates at about 08h local time.

η–Lyrids (ELY)

Active: May 3–14; Maximum: May 9 (λ⊙ = 48°); ZHR = 3; Radiant: α = 287°, δ = +44°; Radiant drift: see Table 6; V∞ = 43 km/s; r = 3.0; TFC: α = 325°, δ = +40° or α = 285°, δ = +15°, and α = 260°, δ = +30° (β > 10° S).

This recent introduction to the Visual Working List is associated with Comet C/1983 H1
IRAS-Araki-Alcock, though it appears to be only a weak shower. Most of the recent observational data
on it has come from purely video results, which have been used to update the parameters above here,
though they also suggested the maximum might fall up to two days later, at λ⊙ = 50° (so
on 2011 May 11). There is little evidence to suggest it has been definitely observed visually as
yet, but the discussion on p. 137 of HMO had more information. Video work, diligent telescopic, or
perhaps equally careful visual, plotting will be needed to separate any potential η–Lyrids from
the sporadics. The general radiant area is usefully on-view all night from the northern hemisphere
(primarily), while the waxing Moon, at first quarter on May 10, sets to leave most of the
post-midnight sky dark enough for useful observing even by May 11.

June Boötids (JBO)

Active: June 22 – July 2; Maximum: June 27, 21h UT (λ⊙ = 95.7°), but see text; ZHR = variable, 0–100+; Radiant: α = 224°, δ = +48°; Radiant drift: see Table 6; V∞ = 18 km/s; r = 2.2; TFC: α = 156°, δ = +64° and α = 289°, δ = +67° (β = 25°–60° N).

This source was reinstated on the Working List after its unexpected return of 1998, when ZHRs of
50–100+ were visible for more than half a day. Another outburst of similar length, but with ZHRs of
∼ 20–50 was observed on 2004 June 23, a date before definite activity had previously been recorded
from this shower.

Consequently, the shower’s start date was altered to try to ensure future activity so early is
caught, and we encourage all observers to routinely monitor throughout the proposed activity period,
in case of fresh outbursts. The predicted possible activity in 2010 was still to come when this text
was prepared. Prior to 1998, only three more probable returns had been detected, in 1916, 1921 and
1927, and with no significant reports between 1928 and 1997, it seemed likely these meteoroids no
longer encountered Earth. The dynamics of the stream were poorly understood, although recent
theoretical modelling has improved our comprehension. The shower’s parent, Comet 7P/Pons-Winnecke,
has an orbit that now lies around 0.24 astronomical units outside the Earth’s at its closest
approach. Its most recent perihelion passage was in 2008 September. Clearly, the 1998 and 2004
returns resulted from material shed by the comet in the past which now lies on slightly different
orbits to the comet itself. Dust trails laid down at various perihelion returns during the 19th
century seem to have been responsible for the last two main outbursts. No predictions for activity
are in-force for 2011, but conditions for checking are very favourable from the mid-northern
latitudes where the radiant is best-seen (indeed it is usefully-observable almost all night from
here), with only a waning crescent Moon on June 27. The prolonged – in some places continuous –
twilight will cause difficulties, however. VID has suggested some June Boötids may be visible
in most years around June 20–25, but with activity largely negligible except near λ⊙ =
92° (2011 June 24), radiating from an area about ten degrees south of the visual one found in
1998 and 2004, close to α α = 216°, δ = +38°.

July to September

The ANT is the chief focus for visual attention during most of July, as its radiant area moves
steadily through eastern Sagittarius, then across northern Capricornus into south-west Aquarius.
Results suggest the Source may not be especially recognisable after the first few days however, as
ZHRs for most of the month seem < 2, and for a time in mid-month even < 1! Activity appears to
improve somewhat, with ZHRs ∼ 2 to 3, by late July and through the first half of August. The large
ANT radiant area now overlaps that of the minor α–Capricornids in July-August, but the
δ–Aquarids are strong enough, and the Piscis Austrinids have a radiant probably distant enough
from the ANT area, that both should still be separable from it, particularly from the southern
hemisphere.

By the best from the major, hopelessly moonlit, Perseids (whose maximum is due sometime between ∼
01h–13h30m UT on August 13, perhaps highest near 06h UT) and the almost equally moonlit
κ–Cygnid peak (probably around August 18, though VID suggested a maximum nearer August 14, and
showed there was some uncertainty in the radiant position), ANT ZHRs will likely have dropped back
below 2 again, as the radiant tracks on through Aquarius, and into western Pisces by the end of
August.

The September-October near-Auriga sources have been re-examined again since the 2010 Shower
Calendar was published, and more changes have been suggested here for them, with alterations in
radiant positions, maxima and active dates. The former September Perseids have not been detected by
VID at all, but the September ε–Perseids and the δ-Aurigids (for a shorter period)
apparently were, so we now list a “new” SPE and the DAU. Further changes have been made to the
Taurids, as the Southern Taurids were detected in early September according to VID, but the Northern
Taurids were not found similarly until late October. Consequently, their parameters have been
changed, as has also that for the ANT, which the Taurids are now considered to replace from
September 10 into early December. In the first ten days of September, ANT rates continue from their
radiant in Pisces, albeit with ZHRs probably no better than 2–3.

ε–Eridanids (EER): Scarcely nothing is known of this possible minor shower. It has
been suggested as associated with Comet C/1854 L1 Klinkerfues. The IMO’s Visual Meteor Database
includes what little information is suspected about it, that its activity is most likely from about
September 9–12, with a maximum around September 10 from a radiant at α = 57°, δ =
−12°. No atmospheric velocity is known for the meteors. In 2011, Jérémie
Vaubaillon has indicated the Earth may encounter the 1600 AD dust trail from Comet Klinkerfues,
which could produce ZHRs of ∼ 40 around 19h34m UT on September 12. The age of the trail, not to
mention the uncertain reality of the shower, means this is extremely uncertain, but observers need
to be alert to the possibility. As this proposed encounter date is at the end of the
previously-suggested activity period, it may be ε–Eridanid meteors could occur beyond
September 12 this year. The radiant can be observed from both hemispheres, but is more favourable
from south of the equator. For mid-northern sites, it rises around local midnight, attaining a
useful elevation by ∼ 02h. From mid-southern latitudes, the radiant rises around 22h and can be
viably observed from midnight onwards. This assumes the theoretical radiant location is correct, of
course! Unhappily, full Moon falls on September 12, thus visual work will be extremely difficult. If
the shower is as strong as predicted though, video and radio systems may be able to detect it, and
if the timing proves accurate, central Indian Ocean locations eastwards across the western half of
Australia (or equivalent longitudes) would be better-placed to cover anything that happens. The
shower should not be confused with other potential Eridanid minor sources, particularly the
ε–Eridanids discovered in analyses of minor shower data during the 1960s by Russian analyst
Alexandra Terentjeva, which was suggested as active from about November 6–28.

For daylight radio observers, the interest of May-June has waned, but there remain the
visually-impossible γ–Leonids (peak due near August 25, 22h UT, albeit not found in recent
radio results), and a tricky visual shower, the Sextantids. Their maximum is expected on September
27, around 22h UT, but possibly it may occur a day earlier. In 1999 a strong return was detected at
λ⊙ ∼ 186°, equivalent to 2011 September 29, while in 2002, the September 27 peak was not
found, but one around September 29–30 was! It seems plausible that several minor maxima in early
October may also be due to this radio shower. New Moon creates near-ideal conditions for visual
observers hoping to catch some Sextantids in the pre-dawn of late September, though radiant-rise is
less than an hour before sunrise in either hemisphere.

Piscis Austrinids (PAU)

Active: July 15 – August 10; Maximum: July 28 (λ⊙ = 125°); ZHR = 5; Radiant: α = 341°, δ = −30°; Radiant drift: see Table 6; V∞ = 35 km/s; r = 3.2; TFC: α = 255° to 0°, δ = 0° to +15°, choose pairs separated by about 30° in α (β < 30° N).

Very little information has been collected on the Piscis Austrinids in recent decades, so the
details on the shower are not well-confirmed, and it seems possible the ZHR may be a little
optimistic. However, that impression may be due simply to the large amount of northern hemisphere
summer data, and the almost complete lack of southern hemisphere winter results, on it. The stream
seems to be rich in faint meteors, rather like the nearby ANT and SDA, so telescopic work is
advisable to try to establish more about it. July’s second New Moon on the 30th means perfect
viewing circumstances for all three southern-sky showers maxima this month.

δ–Aquariids (SDA)

Active: July 12 – August 23; Maximum: July 30 (λ⊙ = 127°); ZHR = 16; Radiant: α = 339°, δ = −16°; Radiant drift: see Table 6; V∞ = 41 km/s; r = 3.2; TFC: α = 255° to 0°, δ = 0° to +15°, choose pairs separated by about 30° in α (β < 40° N).

Like the PAU and ANT, SDA meteors are often faint, thus are suitable targets for telescopic
observing, although enough brighter members exist to make visual and imaging observations worth the
effort too, primarily from more southerly sites. Radio work can pick up the SDA as well, and indeed
the shower has sometimes given a surprisingly strong radio signature. Careful visual plotting is
advised, to help with accurate shower association. The SDA/PAU/ANT/CAP radiants are well above the
horizon for much of the night, and the SDA enjoys identical dark-sky conditions in the second half
of the nights near its maximum to the PAU. Its peak may not be quite so sharp as the single date
here might imply, with perhaps similar ZHRs from July 28–30. Its rates have been suspected of some
variability at times too, though not in the more recent investigations.

α–Capricornids (CAP)

Active: July 3 – August 15; Maximum: July 30 (λ⊙ = 127°); ZHR = 5; Radiant: α = 307°, δ = −10°; Radiant drift: see Table 6; V∞ = 23 km/s; r = 2.5; TFC: α = 255° to 0°, δ = 0° to +15°, choose pairs separated by about 30° in α (β < 40° N); IFC: α = 300°, δ = +10° (β > 45° N), α = 320°, δ = −5° (β 0° to 45° N), α = 300°, δ = −25° (β < 0°).

The CAP and SDA were both definitely detected visually in former years, standing out against the
much weaker other radiants supposed active in Capricornus-Aquarius then. Whether the CAP can still
be detected as visually separate from the new ANT radiant area is unclear, as its radiant now partly
overlaps that of the large ANT region. Observers failed to find a clear maximum for the shower in
2009, which does not augur well, though it had been hoped their bright, at times fireball-class
brilliance, combined with their low apparent velocities, might make them distinctive enough to still
be detected by means other than video. A minor enhancement of CAP ZHRs to ∼ 10 was noted in 1995 by
European IMO observers. Recent results suggest the maximum may continue into July 31.

α–Aurigids (AUR)

Active: August 28 – September 5; Maximum: September 1, 13h UT (λ⊙ = 158.6°); ZHR = 6; Radiant: α = 91°, δ = +39°; Radiant drift: see Table 6; V∞ = 66 km/s; r = 2.6; TFC: α = 052°, δ = +60°; α = 043°, δ = +39° and α = 023°, δ = +41° (β > 10° S).

The shower’s active dates have been changed to be more in-line with the VID findings, and the
radiant position adjusted too. In the past, the shower has produced short, unexpected, outbursts at
times, with EZHRs of ∼ 30–40 recorded in 1935, 1986 and 1994, although they have not been monitored
regularly until very recently, so other events may have been missed. Only three watchers in total
covered the 1986 and 1994 outbursts, for instance!

While badly moonlit, the first predicted outburst happened roughly as expected in 2007, producing
short-lived EZHRs of ∼ 130 for western North America, with many bright meteors. Radio data suggested
there was a ‘tail’ to that event where more faint meteors continued for maybe an hour after the
strongest peak, but visual observers could not confirm this, probably due to the moonlit sky. The
newly-revised AUR radiant reaches a useful elevation only after ∼ 01h local time, and although no
predictions for unusual activity have been made for 2011, the nearly-new Moon provides ideal skies
for whatever may happen.

September ε–Perseids (SPE)

Active: September 4–14; Maximum: September 9, 22h UT (λ⊙ = 166.7°); ZHR = 5; Radiant: α = 47°, δ = +40°; Radiant drift: see Table 6; V∞ = 64 km/s; r = 3.0; TFC: α = 030°, δ = +55°; α = 028°, δ = +35° and α = 025°, δ = +40° (β > 10° S).

This radiant could not be located by VID at all. Instead, what seems to be the
formerly-little-known September ε–Perseid minor shower, or a radiant close to its expected
position, was detected. This radiant was apparently that responsible for producing an unexpected
outburst of swift, bright meteors on 2008 September 9 (from a radiant entred somewhere between
α = 47.5° to 49°, δ = +38° to +43°).

Consequently, the September Perseids have been dropped from the Working List, now replaced by the
September ε–Perseids, with adjusted activity dates and radiant position. The maximum timing
was detected from the recent video analysis and was virtually coincident with the 2008 bright-meteor
outburst. The waxing gibbous Moon, though just three days from full on September 9, will set for
mid-northern sites in time to leave several hours of dark skies for watching still, as the radiant
area remains well on-view all night from about 22h–23h local time onwards.

δ–Aurigids (DAU)

Active: September 20 – October 16; Maximum: October 3 (λ⊙ = 190°); ZHR = 2; Radiant: α = 100°, δ = +44°; Radiant drift: see Table 6; V∞ = 64 km/s; r = 2.9; TFC: α = 80°, δ = +55°; α = 80°, δ = +30° and α = 60°, δ = +40° (β > 10° S).

Neither HMO nor VID were able to confirm the previously-suspected parameters for this minor
source, so the parameters have been completely revised based on what ‘δ–Aurigid’ activity VID
was able to find, as amended by a more thorough examination of this in recent months. This fresh
information is given above, with changes to the active dates (shorter period in particular), maximum
and radiant position. If correct, the 2011 October 3 peak will be free from moonlight, with merely a
waxing crescent Moon, that will have set long before the radiant can be properly observed, after
local midnight.

October to December

A fairly poor final quarter concludes the year, with the more active or interesting showers
having moonlight problems to a greater or lesser extent, leaving dark skies only for some of the
lesser sources. In October, the Draconids peak near full Moon, but may produce an outburst this
year, so are discussed below. The minor Southern Taurid peak is now thought on VID evidence to
happen around October 10 (previous long-standing visual findings suggested November 5), but it will
be very badly moonlit, as also the minor ε–Geminids (peak on October 18). The major Orionids
should reach maximum on October 21, with a last quarter Moon that may be more of a nuisance than a
true deterrent to observers. Their rates are not expected to continue the enhancements seen from
2006–2009 inclusive, but that is not a guarantee! The minor Leonis Minorids are the only really
Moon-free shower peak in the month.

October 5/6 meteors: Short-lived video outbursts were recorded in 2005 and 2006 by
European observers, with activity from a north-circumpolar radiant near the ‘tail’ of Draco, around
α ∼ 165°, δ ∼ +78°, on October 5/6. The meteors showed an atmospheric velocity
of ∼ 45–50 km/s. The 2005 event (only) was recorded very weakly by radio, but no visual results
confirmed either occurrence, and no recurrence was reported in 2007 or 2008. Weak video rates were
claimed detected near the 2009 repeat time, but again, no other method confirmed these, and the
shower was not found by the full ten-year VID analysis. The active interval suggested by video data
lies between λ⊙ ∼ 192.5°–192.8°, equivalent to 2011 October 6, 06h30m–13h50m UT, a
date with a waxing gibbous Moon that will set between midnight and 1 a.m. local time for most
midnorthern sites. If the active interval remains the same this time, it would be best-observed
post-moonset, likely by video only, across North America, the northern Pacific Ocean and the extreme
Far East of Asia.

November sees the Northern Taurid peak, probably still to be found near November 12, too close to
full Moon for observations this year. The Leonids then have a last quarter Moon to contend with, but
might produce unusual activity, possibly on more than one date, so are discussed below. The Moon
will be a waning crescent by the α–Monocerotid peak, around 04h UT on November 22, but with no
strong outburst expected from them, unless something unanticipated chances-by, their usual low
annual activity may well pass virtually unseen in the nuisance-value moonlight.

Some of the early December minor showers survive the waxing Moon, but the minor Monocerotids
(peak around December 9), σ–Hydrids (December 12) and major Geminids (December 14, probably
between 01h–22h UT) do not. The December Leonis Minorids and Comae Berenicids (both with maxima on
December 20) have a waning crescent Moon, again liable to be a particular nuisance because of their
expected weak activity, best-visible for northern hemisphere sites only later in the night, but the
Ursids end the year on a more positively Moon-free note. The ANT starts the quarter effectively
inactive in favour of the Taurids, resuming only around December 10, as the Northern Taurids fade
away, from a radiant centre that tracks across southern Gemini during later December, likely
producing ZHRs < 2, although some of this apparent inactivity may be due to the strength of the
Geminids very close-by to the north during part of December, plus the minor Monocerotids a little
way to its south simultaneously.

Draconids (DRA)

Active: October 6–10; Maximum: October 8, various potential timings – see below; ZHR = periodic, up to storm levels; Radiant: α = 262°, δ = +54°; Radiant drift: negligible; V∞ = 20 km/s; r = 2.6; TFC: α = 290°, δ = +65° and α = 288°, δ = +39° (β > 30° N).

The Draconids are primarily a periodic shower which produced spectacular, brief, meteor storms
twice last century, in 1933 and 1946, and lower rates in several other years (ZHRs ∼ 20–500+). Most
detected showers were in years when the stream’s parent comet, 21P/Giacobini-Zinner, returned to
perihelion, as it did last in 2005 July. Since its orbital period is currently about 6.6 years, it
should return next in 2012 February. In 2005 October, a largely unexpected outburst happened near
the comet’s nodal crossing time, around λ⊙ = 195.40°–195.44°, probably due to
material shed in 1946. Visual ZHRs were ∼ 35, though radar detections suggested a much higher
estimated rate, closer to ∼ 150. The peak was found in radio results too, but it did not record
especially strongly that way. Outlying maximum times from the recent past have spanned from
λ⊙ = 195.075° (in 1998; EZHRs ∼ 700), equivalent to 2011 October 8, 21h10m UT, through
the nodal passage time (λ⊙ = 195.4°, October 9, 05h UT), to λ⊙ =
195.63°–195.76° (a minor outburst in 1999, not a perihelion-return year; ZHRs ∼ 10–20),
equating to 2011 October 9, 10h40m to 13h50m UT. However, of greater note are predictions suggesting
that a number of dust trails laid down between 1873 and 1907 may be encountered this year, in some
cases quite closely, by the Earth on October 8 between ∼ 16h15m–20h10m UT. These were first proposed
by Japanese analyst Mikiya Sato, who indicated too the activity might be quite strong and possibly
persistent for some time during this interval, particularly after 17h. Russian theoretician Mikhail
Maslov has proposed a single peak of not very bright meteors may occur at 20h42m UT, again on
October 8. Of perhaps greatest interest is the still on-going work by Jérémie
Vaubaillon, Juinichi Watanabe and Mikiya Sato, which was not completed at the time the Calendar was
written, but had shown ZHRs might reach ∼ 200 near 19h56m UT on October 8. The strength and timing
of the activity is heavily dependent on assumptions regarding the comet’s orbit, so caution is
advisable, but there is a general consensus that the evening UT hours of October 8 should produce
whatever activity the Draconids are likely to in 2011, sometime between ∼ 16h–21h. Further
predictions and refinements should follow nearer the event.

The Draconid radiant is circumpolar from many northern hemisphere locations, but is highest
during the first half of the night in early October. As noted already, full Moon on October 12 makes
this a difficult year to observe the shower, but the predicted possibly good activity needs to be
checked-for regardless of this. Consequently, observers must just make the best of things, and
observe facing away from the Moon, but not too close to the Draconid radiant, hoping for high rates
of meteors that are not too faint to be hidden in the bright sky! European, west to central Atlantic
Ocean, longitudes would be most-favoured by the better radiant elevations nearest the main peak
times, but anywhere in the northern hemisphere with clear night skies could see something of
whatever happens. Draconid meteors are exceptionally slow-moving, a characteristic which helps
separate genuine shower members from sporadics accidentally lining up with the radiant.

Leonis Minorids (LMI)

Active: October 19–27; Maximum: October 24 (λ⊙ = 211°); ZHR = 2; Radiant: α = 162°, δ = +37°; Radiant drift: see Table 6; V∞ = 62 km/s; r = 3.0; TFC: α = 190°, δ = +58° and α = 135°, δ = +30° (β > 40° N).

This weak minor shower has a peak ZHR apparently on or below the visual threshold, found so far
by video only. The radiant area can be seen solely from the northern hemisphere, where it rises
around midnight. The probable maximum date has scarcely any Moon, just two days from new, so
conditions are about as perfect as possible to confirm whether the shower can be usefully detected
visually. Telescopic, imaging or very careful visual plotting observations are advised.

Leonids (LEO)

Active: November 6–30; Maximum: November 18, 03h40m UT (nodal crossing at λ⊙ = 235.27°), but see below; ZHR = 20+?; Radiant: α = 152°, δ = +22°; Radiant drift: see Table 6; V∞ = 71 km/s; r = 2.5; TFC: α = 140°, δ = +35° and α = 129°, δ = +06° (β > 35° N); or α = 156°, δ = −3° and α = 129°, δ = +6°(β < 35° N). IFC: α = 120°, δ = +40° before 0h local time (β > 40° N); α = 120°, δ = +20° before 4h local time and α = 160°, δ = 0° after 4h local time (β > 0° N); α = 120°, δ = +10° before 0h local time and α = 160°, δ = −10° (β < 0° N).

The most recent perihelion passage of the Leonids’ parent comet, 55P/Tempel-Tuttle, in 1998 may
be more than a decade ago now, but the shower’s activity has continued to be fascinatingly variable
from year to year recently. This year might produce enhanced rates (though these may be observable
using only particularly sensitive radio and radar systems), and theoretical work has suggested there
may be several peaks. Jérémie Vaubaillon has indicated part of the 1800 AD dust trail
may be encountered around 22h36m UT on November 16, and could produce ZHRs of ∼ 200. Unfortunately,
the dust particles involved are expected to be exceptionally small, of order 10–100 microns, and
this could mean no optically-detectable meteors at all. This activity may be observable instead as
an increase in underdense radio meteor echoes, by those systems capable of recording the equivalent
of such ‘invisibly-faint’ meteors, and by sensitive radar meteor systems. Mikhail Maslov has
proposed that there may be two peaks, one on November 17, around 21h UT, when ZHRs may be ∼ 5–10
above the underlying ‘normal’ activity, the second on November 18 near 23h UT, with ZHRs of ∼ 10
above normal. Taking the typical ZHR to be ∼ 10–15 could suggest ZHRs at either might be ∼ 20 ± 5.
The second peak he noted may produce somewhat fainter than average meteors, however. Another
potential maximum time is that given above for the nodal crossing, when ZHRs are liable to be simply
‘normal’.

Whatever the case, the Moon is bright and waning from full on all three dates, with last quarter
on November 18. Thus it will be on-view throughout the time the Leonid radiant is
usefully-observable, from about local midnight onwards (or indeed afterwards south of the equator).
This will make even the typical activity difficult enough to see, but if there are any faint to very
faint meteor maxima as well, these could pass entirely unobserved by optical or imaging methods. The
November 16, and November 18 ∼ 23h, peak timings would be best-detectable for sites at eastern
European longitudes eastwards across most of central Asia. That on November 17 would be similarly
available from places with longitudes equivalent to the Near East east to eastern Asia, while the ∼
04h peak on November 18 would be ideal for European longitudes. Note that other possible maxima are
not excluded by these expectations! All observing techniques can be usefully employed, avoiding
facing the Moon for optical and imaging work, naturally. VID has indicated weak Leonid activity
might be detected for a much longer interval than had been previously suspected, and though this
remains unconfirmed visually, the active dates for the shower have been expanded accordingly this
year.

Phoenicids (PHO)

Active: November 28 – December 9; Maximum: December 6, 21h40m UT (λ⊙ = 254.25°), but see below; ZHR = variable, usually none, but may reach 100; Radiant: α = 18°, δ = −53°; Radiant drift: see Table 6; V∞ = 18 km/s; r = 2.8; TFC: α = 040°, δ = −39° and α = 065°, δ = −62°(β < 10° N).

Only one impressive Phoenicid return has been reported so far, that of its discovery in 1956,
when the EZHR was probably ∼ 100, possibly with several peaks spread over a few hours. Three other
potential bursts of lower activity have been reported, but never by more than one observer, under
uncertain circumstances. Reliable IMO data has shown recent activity to have been virtually
nonexistent. This may be a periodic shower however, and more observations of it are needed by all
methods. From the southern hemisphere (only), the Phoenicid radiant culminates at dusk, remaining
well on view for most of the night. The waxing gibbous Moon sets to leave several pre-dawn hours
with dark skies available for observers around December 6. Jérémie Vaubaillon has
indicated there is the possibility of a Phoenicid return in 2011, from a dust trail left in 1870.
The activity could be so low as to be undetectable regrettably, but it would be worthwhile
checking-for just in case. He suggested this might happen around 09h30m UT on December 1, from a
radiant rather different to the ‘usual’ one, perhaps near α = 6°, δ = −25°. Note
that this position is quite uncertain, and actually lies on the border between Sculptor and Cetus,
around 8° southwest of the star β Ceti, which could make any activity detectable from
places further north than is normally possible. December 1 also has a more favourable waxing
crescent Moon, and that peak’s timing, if correct, would favour sites across the southern Pacific
Ocean from New Zealand east to South America especially.

Puppid-Velids (PUP)

Active: December 1–15; Maximum: December ∼ 7 (λ⊙ ∼ 255°); ZHR ∼ 10; Radiant: α = 123°, δ = −45°; Radiant drift: see Table 6; V∞ = 40 km/s; r = 2.9; TFC: α = 90° to 150°, δ = −20° to −60°; choose pairs of fields separated by about 30° in α, moving eastwards as the shower progresses (β < 10° N).

This is a very complex system of poorly-studied showers, visible chiefly to those south of the
equator. Up to ten sub-streams have been identified, with radiants so tightly clustered, visual
observing cannot readily separate them. Imaging or telescopic work would thus be sensible, or very
careful visual plotting. The activity is so badly-known, we can only be reasonably sure that the
higher rates occur in early to mid December, with a waxing gibbous Moon this year. Some of these
showers may be visible from late October to late January, however. Most Puppid-Velid meteors are
quite faint, but occasional bright fireballs, notably around the suggested maximum here, have been
reported previously. The radiant area is on-view all night, but is highest towards dawn.

Ursids (URS)

Active: December 17–26; Maximum: December 23, 02h UT (λ⊙ = 270.7°), but see below; ZHR = 10 (occasionally variable up to 50); Radiant: α = 217°, δ = +76°; Radiant drift: see Table 6; V∞ = 33 km/s; r = 3.0; TFC: α = 348°, δ = +75° and α = 131°, δ = +66° (β > 40° N); α = 063°, δ = +84° and α = 156°, δ = +64° (β 30° to 40° N).

A very poorly-observed northern hemisphere shower, but one which has produced at least two major
outbursts in the past 70 years, in 1945 and 1986. Several other rate enhancements have been reported
as well, recently in 1988, 1994, 2000, 2006, 2007 and 2008 (which latter apparently produced at
least two peaks with EZHRs of ∼ 30–35, and activity around half this level or better for perhaps
nine to ten hours). Other similar events could have been missed easily 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 λ⊙ = 270.8°, for instance, which
might suggest a slightly later maximum time in 2011 of December 23, ∼ 04h UT. Models developed by
Esko Lyytinen and Jérémie Vaubaillon have suggested the relative proximity of the
shower’s parent comet, 8P/Tuttle, last at perihelion in January 2008, seems to have been what has
influenced some of the recent events. Jérémie’s model has further indicated there
could be another peak this year, around 16h11m UT on December 22, with fairly typical ZHRs of ∼ 12.
VID indicated a maximum around λ⊙ = 270.5°, equal to December 22, ∼ 21h 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. New Moon on December 24
means observing conditions are perfect for checking whatever takes place. The ∼ 16h timing would be
available overnight to observers from eastern European longitudes east across all of Asia; the ∼ 21h
peak would be good for European sites east across most of Asia; and the 02h–04h peaks would fall
best for places from North America east across Europe.

Tables

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.
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.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.

Table 1. Optimum radiant diameters to be assumed for shower
association of minor-shower meteors as a function of the radiant distance D of the meteor.

D	optimum diameter
15°	14°
30°	17°
50°	20°
70°	23°

Note that this radiant diameter criterion applies to all shower radiants except those of
the Southern and Northern Taurids, and the Antihelion Source, all of which have notably larger
radiant areas. The optimum α × δ size to be assumed for each radiant of the
two Taurid showers is instead 20° × 10°, while that for the Antihelion Source is
still larger, at 30° × 15°.

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.

Table 2. Error limits for the angular velocity

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.

Table 3. Angular velocities as a function of the radiant distance of
the meteor (D) and the elevation of the meteor above the horizon (h) for three different geocentric
velocities (V_∞). All velocities are in °/s.

	V∞ = 25 km/s						V∞ = 40 km/s						V∞ = 60 km/s
h  D		10°	20°	40°	60°	90°		10°	20°	40°	60°	90°		10°	20°	40°	60°	90°
10°		0.4	0.9	1.6	2.2	2.5		0.7	1.4	2.6	3.5	4.0		0.9	1.8	3.7	4.6	5.3
20°		0.9	1.7	3.2	4.3	4.9		1.4	2.7	5.0	6.8	7.9		1.8	3.5	6.7	9.0	10
40°		1.6	3.2	5.9	8.0	9.3		2.6	5.0	9.5	13	15		3.7	6.7	13	17	20
60°		2.2	4.3	8.0	11	13		3.5	6.8	13	17	20		4.6	9.0	17	23	26
90°		2.5	4.9	9.3	13	14		4.0	7.9	15	20	23		5.3	10	20	26	30

Table 4. Lunar phases for 2011.

New Moon	First Quarter	Full Moon	Last Quarter
January 4	January 12	January 19	January 26
February 3	February 11	February 18	February 24
March 4	March 12	March 19	March 26
April 3	April 11	April 18	April 25
May 3	May 10	May 17	May 24
June 1	June 9	June 15	June 23
July 1	July 8	July 15	July 23
July 30	August 6	August 13	August 21
August 29	September 4	September 12	September 20
September 27	October 4	October 12	October 20
October 26	November 2	November 10	November 18
Novermber 25	December 2	December 10	December 18
December 24

Table 5. Working list of visual meteor showers.

Details in this Table were correct according to the best information available in May 2010, with
maximum dates accurate only for 2011. Except for the Antihelion Source, all other showers are listed
in order of their maximum solar longitude. An asterisk (‘*’) in the ‘Shower’ column indicates that
source may have additional peak times, as noted in the text above. The parenthesized maximum date
for the Puppids-Velids indicates a reference date for the radiant only, not necessarily a true
maximum. Some showers have ZHRs that vary from year to year. The most recent reliable figure is
given here, except for possibly periodic showers. These are either are noted as ‘Var’ = variable,
where there is considerable uncertainty over the likely maximum rates, or with an asterisk to
indicate the value is that suggested from theoretical considerations for the current year. For more
information, contact the IMO’s Visual Commission.

Shower	Activity	Maximum		Radiant		V∞	r	ZHR
		Date	λ⊙	α	δ	km/s
Antihelion Source (ANT)	Dec 10 – Sep 10	March-April,		see Table 6		30	3.0	4
		late May, late June
Quadrantids (QUA)	Dec 28 – Jan 12	Jan 04	283.16°	230°	+49°	41	2.1	120
α-Centaurids (ACE)	Jan 28 – Feb 21	Feb 08	319.2°	210°	-59°	56	2.0	6
γ-Normids (GNO)	Feb 25 – Mar 22	Mar 15	354°	239°	-50°	56	2.4	6
Lyrids (LYR)	Apr 16 – Apr 25	Apr 22	32.32°	271°	+34°	49	2.1	18
π-Puppids (PPU)	Apr 15 – Apr 28	Apr 24	33.5°	110°	-45°	18	2.0	Var
η-Aquariids (ETA)	Apr 19 – May 28	May 06	45.5°	338°	-01°	66	2.4	70*
η-Lyrids (ELY)	May 03 – May 14	May 09	48.0°	287°	+44°	43	3.0	3
June Bootids (JBO)	Jun 22 – Jul 02	Jun 27	95.7°	224°	+48°	18	2.2	Var
Piscis Austrinids (PAU)	Jul 15 – Aug 10	Jul 28	125°	341°	-30°	35	3.2	5
South. δ-Aquariids (SDA)	Jul 12 – Aug 23	Jul 30	127°	340°	-16°	41	3.2	16
α-Capricornids (CAP)	Jul 03 – Aug 15	Jul 30	127°	307°	-10°	23	2.5	5
Perseids (PER)*	Jul 17 – Aug 24	Aug 13	140.0°	48°	+58°	59	2.2	100
κ-Cygnids (KCG)	Aug 03 – Aug 25	Aug 18	145°	286°	+59°	25	3.0	3
α-Aurigids (AUR)	Aug 28 – Sep 10	Sep 01	158.6°	93°	+39°	67	2.5	6
September ε-Perseids (SPE)	Sep 05 – Sep 21	Sep 10	166.7°	48°	+40°	66	3.0	5
δ-Aurigids (DAU)	Oct 10 – Oct 18	Oct 11	198°	84°	+44°	67	3.0	2
Draconids (DRA)	Oct 06 – Oct 10	Oct 08	195.4°	262°	+54°	20	2.6	Var
Southern Taurids (STA)	Sep 10 – Nov 20	Oct 10	197°	32°	+09°	27	2.3	5
ε-Geminids (EGE)	Oct 14 – Oct 27	Oct 18	205°	102°	+27°	70	3.0	3
Orionids (ORI)	Oct 02 – Nov 07	Oct 21	208°	95°	+16°	66	2.5	25*
Leo Minorids (LMI)	Oct 19 – Oct 27	Oct 24	211°	161°	+38°	62	3.0	2
Northern Taurids (NTA)	Oct 20 – Dec 10	Nov 12	230°	58°	+22°	29	2.3	5
Leonids (LEO)	Nov 06 – Nov 30	Nov 18	235.27°	152°	+22°	71	2.5	20+*
α-Monocerotids (AMO)	Nov 15 – Nov 25	Nov 22	239.32°	117°	+01°	65	2.4	Var
Phoenicids (PHO)	Nov 28 – Dec 09	Dec 06	254.25°	18°	-53°	18	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	2
σ-Hydrids (HYD)	Dec 03 – Dec 15	Dec 12	260°	127°	+02°	58	3.0	3
Geminids (GEM)	Dec 07 – Dec 17	Dec 14	262.2°	112°	+33°	35	2.6	120
Dec. Leonis Minorids (DLM)	Dec 05 – Feb 04	Dec 20	268°	161°	+30°	64	3.0	5
Comae Berenicids (COM)	Dec 12 – Dec 23	Dec 16	264°	175°	+18°	65	3.0	3
Ursids (URS)	Dec 17 – Dec 26	Dec 23	270.7°	217°	+76°	33	3.0	10

Table 6. Radiant positions during the year in α and
δ.

Date	ANT	QUA	DLM
Jan 0	112° +21°	228° +50°	172° +25°
Jan 5	117° +20°	231° +49°	176° +23°
Jan 10	122° +19°	234° +48°	180° +21°
Jan 15	127° +17°		185° +19°
Jan 20	132° +16°		189° +17°
Jan 25	138° +15°		193° +15°	ACE
Jan 30	143° +13°		198° +12°	200° -57°
Feb 5	149° +11°		203° +10°	208° -59°
Feb 10	154° +9°			214° -60°
Feb 15	159° +7°			220° -62°
Feb 20	164° +5°	GNO		225° -63°
Feb 28	172° +2°	225° -51°
Mar 5	177° 0°	230° -50°
Mar 10	182° -2°	235° -50°
Mar 15	187° -4°	240° -50°
Mar 20	192° -6°	245° -49°
Mar 25	197° -7°
Mar 30	202° -9°
Apr 5	208° -11°
Apr 10	213° -13°	LYR	PPU
Apr 15	218° -15°	263° +34°	106° -44°	ETA
Apr 20	222° -16°	269° +34°	109° -45°	323° -7°
Apr 25	227° -18°	274° +34°	111° -45°	328° -5°
Apr 30	232° -19°			332° -3°	ELY
May 5	237° -20°			337° -1°	283° +44°
May 10	242° -21°			341° +1°	288° +44°
May 15	247° -22°			345° +3°	293° +45°
May 20	252° -22°			349° +5°
May 25	256° -23°			353° +7°
May 30	262° -23°
Jun 5	267° -23°
Jun 10	272° -23°
Jun 15	276° -23°
Jun 20	281° -23°	JBO
Jun 25	286° -22°	223° +48°
Jun 30	291° -21°	225° +47°	CAP
Jul 5	296° -20°		285° -16°	SDA
Jul 10	300° -19°	PER	289° -15°	325° -19°	PAU
Jul 15	305° -18°	6° +50°	294° -14°	329° -19°	330° -34°
Jul 20	310° -17°	11° +52°	299° -12°	333° -18°	334° -33°
Jul 25	315° -15°	22° +53°	303° -11°	337° -17°	338° -31°
Jul 30	319° -14°	29° +54°	307° -10°	340° -16°	343° -29°	KCG
Aug 5	325° -12°	37° +56°	313° -8°	345° -14°	348° -27°	283° +58°
Aug 10	330° -10°	45° +57°	318° -6°	349° -13°	352° -26°	284° +58°
Aug 15	335° -8°	51° +58°		352° -12°		285° +59°
Aug 20	340° -7°	57° +58°	AUR	356° -11°		286° +59°
Aug 25	344° -5°	63° +58°	85° +40°			288° +60°
Aug 30	349° -3°		90° +39°	SPE		289° +60°
Sep 5	355° -1°	STA	96° +39°	43° +40°
Sep 10	0° +1°	12° +3°	102° +38°	48° +40°
Sep 15		15° +4°		53° +40°
Sep 20		18° +05°		59° +41°
Sep 25		21° +6°
Sep 30		25° +7°		ORI
Oct 5		28° +8°		85° +14°	DAU		DRA
Oct 10	EGE	32° +9°		88° +15°	82° +45°		262° +54°
Oct 15	99° +27°	36° +11°	NTA	91° +15°	87° +43°	LMI
Oct 20	104° +27°	40° +12°	38° +18°	94° +16°	92° +41°	158° +39°
Oct 25	109° +27°	43° +13°	43° +19°	98° +16°		163° +37°
Oct 30		47° +14°	47° +20°	101° +16°		168° +35°
Nov 5		52° +15°	52° +21°	105° +17°	LEO
Nov 10		56° +15°	56° +22°		147° +24°		AMO
Nov 15		60° +16°	61° +23°		150° +23°		112° +2°
Nov 20		64° +16°	65° +24°		153° +21°		116° +1°
Nov 25			70° +24°	PHO	156° +20°	PUP	120° 0°
Nov 30	ANT	GEM	74° +24°	14° -52°	159° +19°	120° -45°	91° +8°
Dec 5	85° +23°	103° +33°	149° +37°	18° -53°	122° +3°	122° -45°	96° +8°
Dec 10	90° +23°	108° +33°	153° +35°	22° -53°	126° +2°	125° -45°	100° +8°
Dec 15	96° +23°	113° +33°	157° +33°	101° +19°	130° +1°	128° -45°	104° +8°
Dec 20	101° +23°	118° +32°	161° +31°	177° +18°	HYD	217° +76°	MON
Dec 25	106° +22°	QUA	166° +28°	180° +16°		217° +74°
Dec 30	111° +21°	226° +50°	170° +26°	COM		URS
			DLM

Table 7. Working list of daytime radio meteor showers.

An asterisk (‘*’) in the ‘Max date’ column indicates that source may have additional peak times,
as noted in the text above. 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. An asterisk in the ‘Rate’ column shows the suggested rate may not recur in all
years.

Shower	Activity	Max	λ⊙	Radiant		Best observed		Rate
		Date	2000	α	δ	50°N	35°S
Cap/Sagittariids	Jan 13 – Feb 04	Feb 01*	312.5°	299°	-15°	11h-14h	09h-14h	Medium*
χ-Capricornids	Jan 29 – Feb 28	Feb 13*	324.7°	315°	-24°	10h-13h	08h-15h	Low*
Piscids (Apr)	Apr 08 – Apr 29	Apr 20	30.3°	7°	+07°	07h-14h	08h-13h	Low
δ-Piscids	Apr 24 – Apr 24	Apr 24	34.2°	11°	+12°	07h-14h	08h-13h	Low
ε-Arietids	Apr 24 – May 27	May 09	48.7°	44°	+21°	08h-15h	10h-14h	Low
Arietids (May)	May 04 – Jun 06	May 16	55.5°	37°	+18°	08h-15h	09h-13h	Low
ο-Cetids	May 05 – Jun 02	May 20	59.3°	28°	-04°	07h-13h	07h-13h	Medium*
Arietids	May 22 – Jul 02	Jun 07*	76.7°	44°	+24°	06h-14h	08h-12h	High
ζ-Perseids	May 20 – Jul 05	Jun 09*	78.6°	62°	+23°	07h-15h	09h-13h	High
β-Taurids	Jun 05 – Jul 17	Jun 28	96.7°	86°	+19°	08h-15h	09h-13h	Medium
γ-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°	00°	06h-12h	06h-13h	Medium*

Abbreviations

• α, δ: Coordinates for a shower’s radiant position, usually at maximum.
  α is right ascension, δ 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: The 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.
• λ⊙: Solar longitude, a precise measure of the Earth’s position on its orbit which
  is not dependent on the vagaries of the calendar. All λ⊙ are given for the equinox
  2000.0.
• V_∞: Atmospheric or apparent meteoric velocity, given in km/s. Velocities
  range from about 11 km/s (very slow) to 72 km/s (very fast). 40 km/s is roughly medium speed.
• ZHR: Zenithal Hourly Rate, a calculated maximum number of meteors an ideal observer
  would see in perfectly clear skies with the shower radiant overhead. This figure is given in terms
  of meteors per hour. Where meteor activity persisted at a high level for less than an hour, or where
  observing circumstances were very poor, an estimated ZHR (EZHR) is used, which is less accurate than
  the normal ZHR.
• TFC and IFC: Suggested telescopic and still-imaging (including photographic) field
  centres respectively. β 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 IFC 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.