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(meteorobs) IMO 1999 Meteor Shower Calendar
International Meteor Organization
1999 Meteor Shower Calendar (Net-Version)
=========================================
compiled by Alastair McBeath
based on data in IMO Monograph No.2: Handbook for Visual Meteor Observers,
edited by Juergen Rendtel, Rainer Arlt and Alastair McBeath, IMO, 1995; with
additional contributions from Rainer Arlt and Marc de Lignie. Layout by Andre
Knoefel.
Introduction
------------
Welcome to the 1999 International Meteor Organization (IMO) Meteor Shower
Calendar. The year promises to be another interesting one, with many major
showers free from moonlight interference (except the Quadrantids, eta-
Aquarids, Southern delta-Aquarids and Orionids). The Leonids may possibly
produce high to very high activity in November, while in August, the
millennium's last total solar eclipse ensures perfect conditions for the
Perseids. 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 1deg 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 updating from analyses using the IMO's Visual Meteor
Database, the single most accurate listing available anywhere today for
naked-eye meteor observing. Even this can never be a complete list of all
meteor showers, since there are many showers which cannot be properly
detected visually, and some which only photographic, radar, telescopic, or
video observations can separate from the background sporadic meteors, present
throughout the year.
The IMO's aims are to encourage, collect, analyze, and publish combined
meteor data obtained from sites all over the globe in order to further our
understanding of the meteor activity detectable from the Earth's surface.
Results from only a few localized places can never provide such total
comprehension, and it is thanks to the efforts of the many IMO observers
worldwide since 1988 that we have been able to achieve as much as we have to
date. This is not a matter for complacency, however, since it is solely by
the continued support of many people across the whole world that our steps
towards constructing a better and more complete picture of the near-Earth
meteoroid flux can proceed. This means that all meteor workers, wherever they
are and whatever methods they use to record meteors, should follow the
standard IMO observing guidelines when compiling their information, and
submit their data promptly to the appropriate Commission for analysis.
Visual and photographic techniques remain popular for nightly meteor coverage
(weather permitting), although both suffer considerably from the presence of
moonlight. Telescopic observations are less popular, but they allow the fine
detail of shower radiant structures to be derived, and they permit very low
activity showers to be accurately detected. Video methods 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 year's first quarter brings several low activity showers, including the
diffuse ecliptical stream complex, the Virginids, active from late January to
mid-April. Of the two major showers, the northern-hemisphere Quadrantids
(visual peak around January 3, 23h UT) are lost to bright moonlight. The
southern-hemisphere alpha-Centaurids (maximum expected circa February 8, 10h
UT) are somewhat better-placed, but the last quarter Moon rises around local
midnight on February 8, a nuisance as the shower is most observable only
after late evening. However, the minor delta-Cancrids benefit from new Moon
in January, as do the gamma-Normids in March. Daylight radio peaks are due
from the Capricornids/Sagittarids around 20h UT on February 1, and the chi-
Capricornids on February 13, probably around 21h UT. Neither radio shower has
been well-observed in recent times, and as both have radiants under
10deg-15deg west of the Sun at maximum, they cannot be regarded as visual
targets even from the southern hemisphere.
delta-Cancrids
--------------
Active: January 1 - 24; Maximum: January 17 (lambda = 297deg); ZHR = 4;
Radiant: alpha = 130deg, delta = +20deg, Radiant drift: see Table 3;
size: alpha = 20deg x delta = 10deg; V = 28 km/s; r = 3.0;
TFC: alpha = 115deg, delta = +24deg and
alpha = 140deg, delta = +35deg (beta > 40deg N);
alpha = 120deg, delta = -03deg and
alpha = 140deg, delta = -03deg (beta < 40deg N).
This minor stream is well-suited to telescopic observations, with its large,
complex radiant area, that probably consists of several sub-centers. Many of
its meteors are faint. It is probably an early part of the Virginid activity.
Recent observations show the delta-Cancrid ZHR is unlikely to rise much above
3-4, and the visual maximum may fall around lambda = 291deg (1999 January
11). January's new Moon on January 17 provides an excellent opportunity for
checking what happens this year. The long winter nights in the northern
hemisphere provide a further incentive, though the radiant is above the
horizon almost all night, whether your site is north or south of the equator.
Even on January 11, the first half of the night is Moon-free for all
observers.
gamma-Normids
-------------
Active: February 25 - March 22; Maximum: March 14 (lambda = 353deg); ZHR = 8;
Radiant: alpha = 249deg, delta = -51deg, Radiant drift: see Table 3;
Radius: 5deg; V = 56 km/s; r = 2.4;
TFC: alpha = 225deg, delta = -26deg and
alpha = 215deg, delta = -45deg (beta < 15deg S).
gamma-Normid meteors are similar to the sporadics in appearance, and for most
of their activity period, their ZHR is virtually undetectable above this
background rate. The peak itself is normally quite sharp, with ZHRs of 3+
noted for only a day or two to either side of the maximum. Activity may vary
somewhat at times, with occasional broader, or less obvious, maxima having
been reported in the past. Post-midnight watching yields best results, when
the radiant is rising to a reasonable elevation from southern hemisphere
sites. The waning crescent Moon on March 14 rises around or after 02h local
time south of the equator, and should cause only minor problems. All forms of
observation can be carried out for the shower, although most northern
observers will see nothing from it.
April to June
-------------
Meteor activity picks up towards the April-May boundary, with showers like
the Lyrids, pi-Puppids (maximum due around April 24, 02h UT) and eta-Aquarids
(peak between May 5, 10h UT to May 6, 11h UT), with both these latter sources
suffering 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 meteors 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 are as follows:
April Piscids -- April 20, 19h UT;
delta-Piscids -- April 24, 19h UT;
epsilon-Arietids -- May 9, 18h UT;
May Arietids -- May 16, 19h UT;
o-Cetids -- May 20, 17h UT;
Arietids -- June 7, 21h UT;
zeta-Perseids -- June 9, 20h UT;
beta-Taurids -- June 28, 20h UT.
The ecliptical complexes continue with some late Virginids and the best from
the minor Sagittarids in May-June. Visual observers should also be alert for
any possible June Lyrids this year.
Lyrids
------
Active: April 16 - 25; Maximum: April 22, 16h UT (lambda = 32.1deg);
ZHR = 15 (can be variable, up to 90);
Radiant: alpha = 271deg, delta = +34deg, Radiant drift: see Table 3;
Radius: 5deg; V = 49 km/s; r = 2.9;
TFC: alpha = 262deg, delta = +16deg and
alpha = 282deg, delta = +19deg (beta > 10deg S).
The Lyrids are best viewed from the northern hemisphere, but they are
observable from many sites north and south of the equator, and are suitable
for all forms of observation. Maximum rates are generally 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 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 first quarter
Moon sets around 01h-02h local time north of the equator, so will cause only
slight problems in the early post-midnight period. The predicted maximum
should favour sites in Eastern Russia and Asia if correct, but variations in
the stream could mean this is not the case in actuality.
June Lyrids
-----------
Active: June 11 - 21; Maximum: June 16 (lambda = 85deg);
ZHR = variable, 0 - 5;
Radiant: alpha = 278deg, delta = +35deg,
Radiant drift: June 10 alpha = 273deg, delta = +35deg,
June 15 alpha = 277deg, delta = +35deg,
June 20 alpha = 281deg, delta = +35deg;
Radius: 5deg; V = 31 km/s; r = 3.0.
This shower does not feature in the current IMO Working List of Visual Meteor
Showers, as apart from some activity seen from northern hemisphere sites in a
few years during the 1960s (first seen 1966) and 1970s, evidence for its
existence has been virtually zero since. In 1996, several observers
independently reported some June Lyrids, however, and because the shower's
probable maximum benefits from a waxing crescent Moon this year, we urge all
observers who can to cover this possible stream. The radiant is a few degrees
south of the bright star Vega (alpha Lyrae), so will be well on-view
throughout the short northern summer nights, but there are discrepancies in
its position in the literature. All potential June Lyrids should be carefully
plotted, paying especial attention to the meteors' apparent velocity.
Confirmation or denial of activity from this source in 1999 would be very
useful.
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, and finally the Piscids into September. The two strongest sources,
the Southern delta-Aquarids (peak on July 28, 12h UT) and the alpha-
Capricornids (maximum July 30), are lost to July's full Moon, along with the
less-active Piscis Austrinids and the Southern iota-Aquarids. However, the
Pegasids and Phoenicids in July, the Perseids in August and the delta-
Aurigids in September do much better. The Northern delta-Aquarid (around
August 9) and kappa-Cygnid (August 18) maxima should be good too, but the
alpha-Aurigids (peak due around September 1, 12h UT) are another lunar
casualty, together with the most likely Piscid peak, on September 20. For
daylight radio observations, the interest of May-June has waned, but there
remain the visually-inaccessible gamma-Leonids (peak circa August 25, 21h
UT), and a tricky visual shower, the Sextantids (maximum expected September
27, 20h UT). The latter has particular problems from the almost full Moon,
and rises less than an hour before dawn in either hemisphere anyway.
Pegasids
--------
Active: July 7 - 13; Maximum: July 10 (lambda = 107.5deg); ZHR = 3;
Radiant: alpha = 340deg, delta = +15deg, Radiant drift: see Table 3;
Radius: 5deg; V = 70 km/s; r = 3.0;
TFC: alpha = 320deg, delta = +10deg and
alpha = 332deg, delta = +33deg (beta > 40deg N);
alpha = 357deg, delta = +02deg (beta < 40deg N).
Monitoring this short-lived minor shower is not easy, as a few cloudy nights
mean its loss for visual observers, but with the Moon nearly new for its peak
this year, everyone - particularly those in the northern hemisphere - should
attempt to cover it. The shower is best-seen in the second half of the night,
and the Moon will be only a slight distraction near dawn. The maximum ZHR is
generally low, and swift, faint meteors can be expected. Telescopic observing
would be especially useful.
July Phoenicids
---------------
Active: July 10 - 16; Maximum: July 13 (lambda = 111deg);
ZHR = variable 3 - 10, usually <4;
Radiant: alpha = 32deg, delta = -48deg, Radiant drift: see Table 3;
Radius: 7deg; V = 47 km/s; r = 3.0;
TFC: alpha = 041deg, delta = -39deg and
alpha = 066deg, delta = -62deg (beta < 10deg N).
This minor shower can be seen from the southern hemisphere, from where it
only attains a reasonable elevation above the horizon after midnight. This is
an ideal year to watch it, since new Moon falls perfectly for its expected
peak. Activity can be quite variable visually, and indeed observations show
it is a richer radio meteor source (possibly also telescopically too, but
more results are needed). The peak has not been well-observed for some
considerable time, though recent years have brought maximum ZHRs of under 4,
when the winter weather has allowed any coverage at all. More data would be
very welcome!
Perseids
--------
Active: July 17 - August 24; Maxima: August 12, 23h UT (lambda = 139.81deg),
August 13, 05h UT (lambda = 140.03deg) and
August 13, 13h UT (lambda = 140.35deg);
ZHR: primary peak = variable, recently ~120-160, secondary and tertiary peaks =
100;
Radiant: alpha = 46deg, delta = +58deg, Radiant drift: see Table 3;
Radius: 5deg; V = 59 km/s; r = 2.6;
TFC: alpha = 019deg, delta = +38deg and
alpha = 348deg, delta = +74deg before 02h local time;
alpha = 043deg, delta = +38deg and
alpha = 073deg, delta = +66deg after 02h local time (beta > 20deg N);
PFC: alpha = 300deg, delta = +40deg,
alpha = 000deg, delta = +20deg or
alpha = 240deg, delta = +70deg (beta > 20deg N).
The Perseids have become the single most exciting and dynamic meteor shower
in recent times, with outbursts producing EZHRs of 400+ in 1991 and 1992,
decreasing to around 300 in 1993, 220 in 1994 and ~120-160 since, at the
shower's primary maximum. Allowing for an average annual shift of ~+0.05deg
in lambda since 1991, this peak is expected to fall around 23h UT on August
12. Other timing variations cannot be ruled-out, however. A new feature in
1997 was a tertiary peak, of strength comparable to the traditional
(currently secondary) maximum, but a few hours after it. The timing for this
third peak is based on just this one return, but there are no guarantees it
will recur in 1999. Even now, as the Perseids' parent comet, 109P/Swift-
Tuttle, returns to the outer Solar System after its 1992 perihelion passage,
the shower can still spring surprises! The August new Moon provides the
perfect opening for all watchers, certainly. As the radiant rises throughout
the night for the northern hemisphere, near and post-midnight watching is
most valuable. If the maxima appear as predicted the places to be should be
Europe; Eastern North America; Far Eastern Siberia, Alaska and the Northern
Pacific Ocean, respectively.
Visual and photographic observers should need little encouragement to cover
this stream, but telescopic and video watching near the main peak would be
valuable in confirming or clarifying the possibly multiple nature of the
Perseid radiant, something not detectable visually. Radio data would
naturally enable early confirmation, or detection, of perhaps otherwise
unobserved maxima if the timings prove unsuitable for land-based sites. The
only negative aspect to the shower is the impossibility of covering it from
the bulk of the southern hemisphere.
delta-Aurigids
--------------
Active: September 5 - October 10; Maximum: September 9 (lambda = 166deg); ZHR =
6;
Radiant: alpha = 60deg, delta = +47deg, Radiant drift: see Table 3;
Radius: 5deg; V = 64 km/s; r = 3.0;
TFC: alpha = 052deg, delta = +60deg;
alpha = 043deg, delta = +39deg and
alpha = 023deg, delta = +41deg (beta > 10deg S).
An essentially northern hemisphere shower, badly in need of more
observations. The delta-Aurigids are actually part of a series of showers
with radiants in Aries, Perseus, Cassiopeia and Auriga, active from late
August into October. They typically produce low rates of generally faint
meteors, and have yet to be well-seen in more than an occasional year.
Circumstances are perfect for their peak in 1999, with new Moon on September
9. Telescopic data to examine all the radiants in this region of sky - and
possibly observe the telescopic beta-Cassiopeids simultaneously - would be
especially useful, but photographs, video records and visual plotting would
be welcomed too. The delta-Aurigid radiant is at a useful elevation from
roughly 23h-00h onwards, so protracted watching is distinctly possible.
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. Before then is a
moonless Draconid epoch, together with badly Moon-affected epsilon-Geminid
and Orionid maxima, all in October. The Orionids' central peak is likely
around 20h UT on October 21 for radio observers. The Leonids in November may
still be capable of producing high to storm activity this year, but the
alpha-Monocerotids (November 22, 01h UT) are lost to the Moon. December's new
Moon is excellent news for covering the chi-Orionids, Phoenicids, Puppid-
Velids, Monocerotids and sigma-Hydrids, along with the Geminids. The downside
is losing the Coma Berenicids and Ursids (peak due circa December 22, 23h UT)
to full Moon.
Draconids
---------
Active: October 6 - 10; Maximum: October 9, 03h UT (lambda = 195.4deg);
ZHR = periodic, up to storm levels;
Radiant: alpha = 262deg, delta = +54deg, Radiant drift: negligible;
Radius: 5deg; V = 20 km/s; r = 2.6;
TFC: alpha = 290deg, delta = +65deg and
alpha = 288deg, delta = +39deg (beta > 30deg N).
New Moon perfectly favours any Draconids that appear this year. Unfortunately
for potential observers, although this periodic shower has produced
spectacular, brief, meteor storms twice already this century, in 1933 and
1946, and lower rates in several other years (ZHRs ~20-200+), so far,
detectable activity has only been seen in years when the stream's parent
comet, 21P/Giacobini-Zinner, has returned to perihelion. It did this last in
1998 November. The peak time above is based on the Earth's closest approach
to the comet orbit's node, but activity might be seen before or considerably
after this too. The radiant is circumpolar from many locations, but is higher
in the pre-midnight and near-dawn hours on October 8-10. The shower is only
properly observable from the northern hemisphere.
Taurids
-------
Southern Taurids
----------------
Active: October 1 - November 25; Maximum: November 5 (lambda = 223deg); ZHR = 5;
Radiant: alpha = 52deg, delta = +13deg, Radiant drift: see Table 3;
Size: alpha = 20deg x delta = 10deg; V = 27 km/s; r = 2.3;
TFC: Choose fields on the ecliptic and ~10deg E or W of the radiants (beta >
40deg S).
Northern Taurids
----------------
Active: October 1 - November 25; Maximum: November 12 (lambda = 230deg); ZHR =
5;
Radiant: alpha = 58deg, delta = +22deg, Radiant drift: see Table 3;
Size: alpha = 20deg x delta = 10deg; V = 29 km/s; r = 2.3;
TFC: as Southern Taurids.
These two streams forms a complex associated with Comet 2P/Encke. Defining
their radiants is best achieved by careful visual or telescopic plotting,
photography or video work, since they are large and diffuse. The brightness
and relative slowness of many shower meteors makes them ideal targets for
photography, while these factors coupled with low, steady combined Taurid
rates makes them excellent targets for newcomers to practice their plotting
techniques on. The activity of both streams produces an apparently plateau-
like maximum for about ten days in early November, and the shower has a
reputation for producing some superbly bright fireballs at times, although
seemingly not in every year. In 1995, an impressive crop of brilliant Taurids
occurred between late October and mid-November, for instance. New Moon on
November 8 means the entire Taurid peak should be treated to dark skies in
1999.
The near-ecliptic radiants for both shower branches mean all meteoricists can
observe the streams. Northern hemisphere observers are somewhat better-
placed, as here suitable radiant zenith distances persist for much of the
late autumnal nights. Even in the southern hemisphere, a good 3-5 hours'
watching around local midnight is possible with Taurus well above the
horizon, however.
Leonids
-------
Active: November 14 - 21; Maximum: November 17, 23h UT (lambda = 235.16deg);
ZHR = 100+ (45 in 1996, ~150? in 1997), but may reach storm level in 1999;
Radiant: alpha = 153deg, delta = +22deg, Radiant drift: see Table 3;
Radius: 5deg; V = 71 km/s; r = 2.9;
TFC: alpha = 140deg, delta = +35deg and
alpha = 129deg, delta = +06deg (beta > 35deg N); or
alpha = 156deg, delta = -03deg and
alpha = 129deg, delta = +06deg (beta < 35deg N).
PFC: before 00h local time alpha = 120deg, delta = +40deg (beta > 40deg N);
before 04h local time alpha = 120deg, delta = +20deg
and after 04h local time alpha = 160deg, delta = 00deg (beta > 00deg N);
before 00h local time alpha = 120deg, delta = +10deg (beta > 40deg N);
and alpha = 160deg, delta = -10deg (beta < 00deg N).
The perihelion passage of the Leonids' parent comet, 55P/Tempel-Tuttle, in
1998 February means high to storm-level Leonid activity may occur in 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! Recent visual IMO International Leonid Watch and radio observations
suggest a peak timing around lambda = 235.16deg is most likely, but another
plausible time is when the Earth passes the node of the comet's orbit, at
lambda = 235.25deg (1999 November 18, 01h UT).
The radiant rises only around local midnight (or indeed afterwards south of
the equator), by which time the waxing gibbous Moon will be setting. Either
suggested peak timing would favour locations in Europe, North Africa, the
Near and Middle East plus European Russia. Even a minor variation in the
peak's occurrence 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 1998 return. All observing methods should be
utilised to the full, especially photography and video if a storm manifests.
chi-Orionids
------------
Active: November 26 - December 15; Maximum: December 2 (lambda = 250deg); ZHR =
3;
Radiant: a = 82deg, delta = +23deg, Radiant drift: see Table 3;
Radius: 8deg; V = 28 km/s; r = 3.0;
TFC: alpha = 083deg, delta = +09deg and
alpha = 080deg, delta = +24deg (beta > 30deg S).
A weak visual stream, but moderately active telescopically. Some brighter
meteors have been photographed too. The shower has at least a double radiant,
but the southern branch has been rarely detected. The chi-Orionids may be a
continuation of the ecliptic complex after the Taurids cease to be active.
The radiant used here is a combined one, suitable for visual work, although
telescopic or video observations should be better-able to determine the exact
radiant structure. The waning crescent Moon should give few problems, as the
radiant is well on display in both hemispheres throughout the night.
Phoenicids
----------
Active: November 28 - December 9; Maximum: December 6, 20h UT (lambda =
254.25deg);
ZHR = variable, usually 3 or less, may reach 100;
Radiant: alpha = 18deg, delta = -53deg, Radiant drift: see Table 3;
Radius: 5deg; V = 18 km/s; r = 2.8;
TFC: alpha = 040deg, delta = -39deg and
alpha = 065deg, delta = -62deg (beta < 10deg N).
Only one impressive Phoenicid return has so far been reported, that of its
discovery in 1956, when the ZHR was ~100. Three other potential bursts of
lower activity have been reported, but never by more than one observer, under
uncertain circumstances. Reliable IMO data shows recent activity to be
virtually nonexistent. This may be a periodic shower, however, and more
observations of it are needed by all methods. Radio workers may find
difficulties, as radar echoes from the 1956 event were only 30 per hour,
perhaps because these low-velocity meteors produce too little radio-
reflecting ionization. Observing conditions this year are excellent for all
southern hemisphere watchers, with new Moon on December 7. The radiant is
well on view for most of the night, but culminates at dusk.
Puppid-Velids
-------------
Active: December 1 - 15; Maximum: December ~7 (lambda ~ 255deg); ZHR ~10;
Radiant: alpha = 123deg, delta = -45deg, Radiant drift: see Table 3;
Radius: 10deg; V = 40 km/s; r = 2.9;
TFC: alpha = 090deg to 150deg, delta = -20deg to -60deg;
choose pairs of fields separated by about 30deg in a, moving
eastwards as the shower progresses (b < 10deg 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.
Photographic, video 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 highest rates occur in early to mid December,
perfect for the new Moon period this year. Some of these showers may visible
from late October to late January. Most shower 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.
Monocerotids
------------
Active: November 27 - December 17; Maximum: December 9 (lambda = 257deg); ZHR =
3;
Radiant: alpha = 100deg, delta = +08deg, Radiant drift: see Table 3;
Radius: 5deg; V = 42 km/s; r = 3.0;
TFC: alpha = 088deg, delta = +20deg and
alpha = 135deg, delta = +48deg (beta > 40deg N); or
alpha = 120deg, delta = -03deg and
alpha = 084deg, delta = +10deg (b < 40deg N).
Only low visual rates can be expected from this source, making accurate
visual plotting, telescopic or video work essential, particularly because the
meteors are normally faint. The shower details, even including the radiant
position, are rather uncertain. Recent IMO data shows only weak signs of a
maximum as indicated above. Telescopic data suggests a later maximum, around
December 16 (lambda ~264deg) from a radiant at alpha = 117deg, delta =
+20deg. This is a very good year for all meteor workers to make observations
to help resolve these points, as the Moon is not a problem. The radiant is
on-show nearly all night, culminating around 01h local time.
sigma-Hydrids
-------------
Active: December 3 - 15; Maximum: December 12 (lambda = 260deg); ZHR = 2;
Radiant: alpha = 127deg, delta = +02deg, Radiant drift: see Table 3;
Radius: 5deg; V = 58 km/s; r = 3.0;
TFC: alpha = 095deg, delta = 00deg and
alpha = 160deg, delta = 00deg (all sites, after midnight only).
Although first detected in the 1960s by photography, sigma-Hydrids are
typically swift and faint, and rates are generally very low, close to the
visual detection threshold. Since their radiant, a little over 10deg east of
the star Procyon (alpha Canis Minoris), is near the equator, all observers
can cover this shower. The radiant rises in the late evening hours, but is
best viewed after local midnight. This means the waxing crescent Moon will
have set long before sigma-Hydrid watching can begin at their peak in 1999.
Recent data indicates the peak may occur up to six days earlier than
suggested above, and would benefit from visual plotting, telescopic or video
work to pin it down more accurately.
Geminids
--------
Active: December 7 - 17; Maximum: December 14, 11h UT (lambda = 262.0deg); ZHR
= 120;
Radiant: alpha = 112deg, delta = +33deg, Radiant drift: see Table 3;
Radius: 5deg; V = 35 km/s; r = 2.6;
TFC: alpha = 087deg, delta = +20deg and
alpha = 135deg, delta = +49deg before 23h local time,
alpha = 087deg, delta = +20deg and
alpha = 129deg, delta = +20deg after 23h local time (beta > 40yN);
alpha = 120deg, delta = -03deg and
alpha = 084deg, delta = +10deg (beta < 40deg N).
PFC: alpha = 150deg, delta = +20deg and
alpha = 060deg, delta = +40deg (beta > 20deg N);
alpha = 135deg, delta = -05deg and
alpha = 080deg, delta = 00deg (beta < 20deg N).
One of the finest annual showers presently observable. The waxing crescent
Moon will have set by about 22h-23h local time at their peak, so much of the
second half of the night at least will be available for observing them. Well
north of the equator, their radiant rises around sunset, and is at a usable
elevation from the local evening hours onwards. 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, so the best activity may occur a little
before or, more likely, after, the suggested time above, perhaps up to
15h-16h UT. This means North American to Far Eastern sites are most likely to
see the best from the 1999 Geminids. Some mass-sorting within the stream
means the fainter telescopic meteors should be most abundant almost 1deg 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 methods
can be employed to observe the shower.
Abbreviations
-------------
alpha, delta: Coordinates for a shower's radiant position, usually at
maximum. alpha is right ascension, delta is declination. Radiants drift
across the sky each day due to the Earth's own orbital motion around
the Sun, and this must be allowed for using the details in Table 3 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.
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 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 PFC: Suggested telescopic and small-camera 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 centers to use for video camera fields as well.
--------------------------------------------------------------------------
Table 1. Lunar phases for 1999.
New Moon First Quarter Full Moon Last Quarter
January 02 January 09
January 17 January 24 January 31 February 08
February 16 February 23 March 02 March 10
March 17 March 24 March 31 April 09
April 16 April 22 April 30 May 08
May 15 May 22 May 30 June 07
June 13 June 20 June 28 July 06
July 13 July 20 July 28 August 04
August 11 August 19 August 26 September 02
September 09 September 17 September 25 October 02
October 09 October 17 October 24 October 31
November 08 November 16 November 23 November 29
December 07 December 16 December 22 December 29
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Table 2: Working list of visual meteor showers. Details in this Table were
correct according to the best information available in June 1998. 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.
Activity Maximum Radiant
Shower Period Date lambda alpha delta
[deg] [deg] [deg]
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 08 319.2 210 -59
delta-Leonids Feb 15-Mar 10 Feb 25 336 168 +16
gamma-Normids Feb 25-Mar 22 Mar 14 353 249 -51
Virginids Jan 25-Apr 15 (Mar 25)(004) 195 -04
Lyrids Apr 16-Apr 25 Apr 22 032.1 271 +34
pi-Puppids Apr 15-Apr 28 Apr 24 033.5 110 -45
eta-Aquarids Apr 19-May 28 May 06 045.5 338 -01
Sagittarids Apr 15-Jul 15 (May 20)(059) 247 -22
Pegasids Jul 07-Jul 13 Jul 10 107.5 340 +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 09 136 335 -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 09 166 060 +47
Piscids Sep 01-Sep 30 Sep 20 177 005 -01
Draconids Oct 06-Oct 10 Oct 09 195.4 262 +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 17 235.16 153 +22
alpha-Monocerotids Nov 15-Nov 25 Nov 22 239.32 117 +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 14 262 112 +33
Coma Berenicids Dec 12-Jan 23 Dec 20 268 175 +25
Ursids Dec 17-Dec 26 Dec 22 270.7 217 +76
IMO
Shower v r ZHR Code
[km/s]
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 2.6 140 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 2.5 100+ 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 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 45deg 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 alpdot del. 50 N 35 S
Cap/Sagittarids Jan 13-Feb 04 Feb 01 312.5 299 -15 11h-14h 09h-14h medium
chi-Capricornids Jan 29-Feb 28 Feb 13 324.7 315 -24 10h-13h 08h-15h low
Piscids (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 09 048.7 044 +21 08h-15h 10h-14h low
Arietids (May) May 04-Jun 06 May 16 055.5 037 +18 08h-15h 09h-13h low
o-Cetids May 05-Jun 02 May 20 059.3 028 -4 07h-13h 07h-13h medium
Arietids May 22-Jul 02 Jun 07 076.7 044 +24 06h-14h 08h-12h high
zeta-Perseids May 20-Jul 05 Jun 09 078.6 062 +23 07h-15h 09h-13h high
beta-Taurids Jun 05-Jul 17 Jun 28 096.7 086 +19 08h-15h 09h-13h medium
gamma-Leonids Aug 14-Sep 12 Aug 25 152.2 155 +20 08h-16h 10h-14h low
Sextantids Sep 09-Oct 09 Sep 27 184.3 152 0 06h-12h 06h-13h medium
---------------------------------------------------------------------------
Useful addresses
----------------
For more information on observing techniques, and when submitting
results, please contact the appropriate IMO Commission Director:
Fireball Data Center (FIDAC): A. Knoefel, Saarbruecker Strasse 8, D-40476
Duesseldorf, Germany. e-mail: fidac@imodot net
Photographic Commission: M. de Lignie, Prins Hendrikplein 42, NL-2264 SN
Leidschendam, The Netherlands. e-mail: photo@imodot net
Radio Commission: Temporarily vacant. e-mail: radio@imodot net
Telescopic Commission: M. Currie, 25 Collett Way, Grove, Wantage, Oxon.
OX12 0NT, UK. e-mail: tele@imodot net
Visual Commission: R. Arlt, Friedenstrasse 5, D-14109 Potsdam, Germany.
email: visual@imodot net
or contact IMO's Homepage on the World-Wide-Web: http://www.imodot net/
For further details on IMO membership, please write to: Ina Rendtel,
IMO Treasurer, Mehlbeerenweg 5, D-14469 Potsdam, Germany. e-mail:
treasurer@imodot 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!