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.

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).

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!

Aquarid Complex

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).

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.

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).

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.

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).

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.

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).

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.

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).

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.