July to September

The minor Pegasid shower is spoilt by last quarter Moon at its
July 9 maximum, but the usually minor July Phoenicids are nearly
Moon-free. Other minor shower activity continues from various
near-ecliptic sources throughout the quarter, first from the
Sagittarids till mid July, then from the Aquarids and
Capricornids, and finally the Piscids into September. The two
stronger sources are lost near full Moon in late July, the
Southern delta-Aquarids (peak on July 27) and the
alpha-Capricornids (maximum July 29), along with the minor
Piscis Austrinids (best around July 27), and the Southern
iota-Aquarids (highest ZHRs of just 2 due around August 4).
However, the Northern delta-Aquarid maximum survives the Moon,
and this year's Perseid peak is timed to be only slightly
moonlit. Better conditions persist for the best from the minor
kappa-Cygnids and the very weak Northern iota-Aquarids as
well. Leap-year means the alpha-Aurigid maximum moves up to
August 31, around 18h UT, too close to full Moon on August 30
to be seen, but the delta-Aurigids have fewer such problems in
early September. For daylight radio observers, the interest of
May-June has waned, but there remain the visually impossible
gamma-Leonids (peak circa August 25, 3h UT, albeit not
found in recent radio results), and a tricky visual shower, the
Sextantids (annual maximum expected on September 27, 3h UT, but
possibly occurring a day earlier. In 1999 a strong return was
detected at sol 186° though, equivalent to 2004 September 28).
Full Moon gives added difficulties for visual observers hoping
to catch some Sextantids in late September, though the radiant
rises less than an hour before dawn in either hemisphere anyway.

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July Phoenicids

  
  Active  : July 10-16;  
  Maximum  : July 13 (sol = 111°);  
  ZHR   = variable 3-10;  
  Radiant  : alpha = 032° , delta = -48°;  
  Radiant drift: see Table 3;  
  V   = 47 km/s;  
  r   = 3.0;  
  TFC   : alpha = 041°, delta = -39° and  
      alpha = 066°, delta = -62° (beta<10° N).  
   
  

Figure 7: Radiant position and drift of the July Phoenicids

This minor shower can be seen from the southern hemisphere, from
where it attains a reasonable elevation above the horizon after
midnight. This is a good year to watch it, since the waning
crescent Moon will rise only around 3h 30m-4h local time,
and will not be much of a distraction even so. Visual activity
can be quite variable, and indeed observations show it to be a
richer radio meteor source (possibly also telescopically too;
more results are needed). The peak has not been well-observed
for some considerable time. 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!

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Aquarid Complex

Northern delta-Aquarids

  
  Active  : July 15-August 25;  
  Maximum  : August 8 (sol = 136°);  
  ZHR   = 4;  
  Radiant  : alpha = 335° , delta = -05°;  
  Radiant drift: see Table 6;  
  V   = 42 km/s;  
  r   = 3.4;  
  TFC   : alpha = 255° to 0°, alpha = 0° to +15°,  
      choose pairs separated by about 30° in alpha (beta<30° N).  
  

Northern iota-Aquarids

  
  Active  : August 11-31;  
  Maximum  : August 19 (sol = 147°);  
  ZHR   = 3;  
  Radiant  : alpha = 327°, delta = -6°;  
  Radiant drift: see Table 6;  
  V   = 31 km/s;  
  r   = 3.2;  
  TFC   : alpha = 255° to 0°, delta = 0° to +15°,  
      choose pairs separated by about 30° in alpha (beta<40° N).  
   
  

Figure 8: Radiant position and drift of the Aquarid radiant complex

The Aquarids are all streams rich in faint meteors, making them
well-suited to telescopic work, although enough brighter members
exist in the delta-Aquarids especially to make visual and
photographic observations worth the effort too, primarily from
more southerly sites. The concentration of radiants around
Aquarius-Capricornus-Piscis Austrinus means observations with shower
association in the field will be highly inaccurate.
Visual watchers in particular should plot any potential
members of all of these radiants rather than
trying to make shower associations directly under the sky.

In 2004, less strong moonlight favours only these two sources,
neither of which are particularly active. The Northern
iota-Aquarids showed an ill-defined maximum between sol =
148°-151° in 1988-1995 results, which could mean the highest
rates (even so, very weak) happen several days after the
suspected peak time given here. The early-setting crescent Moon
on August 19 leaves plenty of dark skies for observing overnight
then, even up to four days later and first quarter Moon. All
these radiants are above the horizon for much of the night.

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Perseids

  
  Active  : July 17-August 24;  
  Maxima  : August 12, 11h - 13h 20m UT (sol = 140.0°-140.1°), possible feature,  
  ZHR   = 100;  
  Radiant  : alpha = 046°, delta = +58°;  
  Radiant drift: see Table 3;  
  V   = 59 km/s;  
  r   = 2.6;  
  TFC   : alpha = 019°, delta = +38° and  
      alpha = 348°, delta = +74° before 2h local time;  
      alpha = 043°, delta = +38° and  
      alpha = 073°, delta = +66° after 2h local time (beta>20° N);  
  PFC   : alpha = 300°, delta = +40°,  
      alpha = 000°, delta = +20° or  
      alpha = 240°, delta = +70° (beta>20° N).  
   
  

Figure 9: Radiant position and drift of the Perseids

The Perseids were one of the most exciting and dynamic meteor
showers during the 1990s, with outbursts at a new primary
maximum producing EZHRs of 400+ in 1991 and 1992. Rates from
this peak decreased to 100-120 by the late 1990s, and since
2000, it has failed to appear. This was not unexpected, as the
outbursts and the primary maximum (which was not noticed before
1988), were associated with particles accompanying the
parent comet 109P/Swift-Tuttle passing perihelion in 1992. The comet's
orbital period is about 130 years, so it is now receding back
into the outer Solar System, and theory predicts that such
outburst rates should dwindle as the comet to Earth distance
increases. An average annual shift of +0.05° in sol had been
deduced from 1991-1999 data, and allowing for this could give a
possible primary peak time around 11h UT on August 12 (sol =
140.01°) coinciding with the most probable maximum time of the
“traditional” peak always previously found, given above. Another
feature, seen only in IMO data from 1997-1999, was a tertiary peak
at sol = 140.4°, the repeat time for which would be shortly
before 21h UT on August 12. Some researchers commented several
years ago that 2004 might see a return of the primary peak for a
year or two. Esko Lyytinen has produced more details refining
this, which suggests the Earth will pass 0.0012 astronomical
units (about 180,000 km) from the dust trail laid down at Comet
Swift-Tuttle's 1862 return at sol = 139.441°, 20h 54m UT on
August 11. While very uncertain, he indicates ZHRs could be 100
then, with a slight possibility of higher rates still, perhaps
even up to storm levels, although the FWHM could be very short,
perhaps just 15 minutes. However, this could be set against a
background of higher general Perseid activity, thanks to the
influence of Jupiter on the meteoroid stream, and the date
should bring strengthening pre-maximum Perseid rates in any case.

Whatever happens, and whenever the peak or peaks fall on August
11 or 12, the waning crescent Moon, four days from new on August
12, will be only a minor nuisance, though it will be rising
around local midnight to 1h from mid-northern latitudes, in
Taurus to Gemini. The radiant rises throughout the night for
these more favourable locations, from where useful watching can
commence an hour or two before local midnight. The various
potential maxima would be best-viewed from: eastern Europe and
eastern North Africa east to central Russia, India and western
China (the additional August 11, 21h UT model prediction),
the extreme east of
Russia and possibly the Japanese island of Hokkaido east to the
extreme western USA (August 12, 11h UT); eastern Russia and
eastern China east to Alaska (August 12, 13h 20m UT).

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. Recent video results have
shown a very simple, single radiant structure certainly. Radio
data would naturally enable early confirmation, or detection, of
perhaps otherwise unobserved maxima if the timings or weather
conditions 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.

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kappa-Cygnids

  
  Active  : August 3-25;  
  Maximum  : August 17, (sol = 145°);  
  ZHR   = 3;  
  Radiant  : alpha = 286°, delta= +59°;  
  Radiant drift: see Table 6;  
  V   = 25 km/s;  
  r   = 3.0;  
  TFC   : alpha = 330°, delta = +60° and  
      alpha = 300°, delta = +30° (beta> 20° N).  
   
  

Figure 10: Radiant position of the kappa-Cygnids

New Moon on August 16 creates perfect viewing conditions for the
expected kappa-Cygnid peak this year, but the shower is chiefly
accessible from the northern hemisphere only. Its r-value
suggests telescopic and video observers may benefit from its
presence, but visual and photographic workers should note that
occasional slow fireballs from this source have been reported
too. Its almost stationary radiant results from its close
proximity to the ecliptic north pole in Draco. There has been
some suggestion of a variation in its activity at times, perhaps
coupled with a periodicity in fireball sightings, but more data
are urgently needed on a shower that is often ignored in favour
of the Perseids during August.

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delta-Aurigids

  
  Active  : September 5 - October 10;  
  Maximum  : September 9 (sol = 166.7°);  
  ZHR   = 5;  
  Radiant  : alpha = 060° , delta = +47°;  
  Radiant drift: see Table 6;  
  V   = 64 km/s;  
  r   = 2.9;  
  TFC   : alpha = 052°, delta = +60°,  
      alpha = 043°, delta = +39° and  
      alpha = 023°, delta = +41° (beta>10° S).  
   
  

Figure 11: Radiant position and drift of the alpha- and delta-Aurigids

A detailed, fresh analysis of the low-activity, and
little-studied, delta-Aurigids was carried out by Audrius
Dubietis and Rainer Arlt using IMO data from 1991-2001 in
2002. This demonstrated the shower probably represents a
combination of two separate, but possibly related, minor
sources, the September Perseids, for which the maximum time given above
holds, and the delta-Aurigids, whose
activities and radiants effectively overlap one another. The
showers are probably not resolvable by visual watchers, who are
advised to retain the, slightly amended, shower parameters
listed above. The actual delta-Aurigid phase seems to give a weak
maximum around sol = 181° (2004 September 23; ZHR 3,
r= 2.5). The shower is essentially a northern hemisphere event,
and it needs to be noted that there is a series
of poorly observed radiants in or near Aries,
Perseus, Cassiopeia and Auriga, active from late August to
October. British and Italian observers independently reported a
possible new radiant in Aries during late August 1997 for
example.

The radiant reaches a useful elevation after 23h-0h
local time, unfortunately around waning crescent moonrise on
September 8/9, though this should not be too great a
distraction. The waxing gibbous Moon sets about this time on
September 23 at least! Telescopic data to examine all the
radiants in this region of sky – and possibly observe the
telescopic beta-Cassiopeids simultaneously – would be
especially valuable, but photographs, video records and visual
plotting would be welcomed too.

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Piscids

  
  Active  : September 1-30;  
  Maximum  : September 19, (sol = 177°);  
  ZHR   = 3;  
  Radiant  : alpha = 5°, delta= -1°;  
  Radiant drift: see Table 6;  
  V   = 26 km/s;  
  r   = 3.0;  
  TFC   : alpha = 340° to 20°, delta = -15° to +15°,  
      choose pairs of fields separated by about 30° in alpha (beta any).  
   
  

Figure 12: Radiant position and drift of the Piscids

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