The minor Pegasids (maximum: July 9) and July Phoenicids (peak on July 13) fall prey to full Moon this year. Next, the near-ecliptic, low activity, Sagittarids end in mid-month, as the various Aquarid sources and the α-Capricornids take up the ecliptical shower complex theme until August. New Moon especially favours all the late-July shower peaks, up to the minor Southern ι-Aquarids in early August. The theoretical Northern δ-Aquarid maximum on August 8, and the major Perseids (whose maximum is most likely between 23h —1h30m UT on August 12 —13, though other peaks on August 13 around 2h and 9h UT are also possible from recent past results), both suffer badly from August’s full Moon. Simulations by Peter Brown made some years ago suggest enhanced Perseid activity is possible this year, though perhaps not as strongly as in 2004. The timing of any enhancement, though probably not far from the expected spread of possible maxima noted here, is not known. Conditions improve after then for the minor κ-Cygnid and Northern ι-Aquarid peaks. In early September, the α-Aurigid maximum in early September survives the bright Moon, but the minor δ-Aurigid peak on September 9 is lost to lunar glare. Their possible second, weaker, maximum is much better placed later in the month, as is the likely best from the Piscids. For daylight radio observers, the interest of May-June has waned, but there remain the visually impossible γ-Leonids (peak towards August 25, 15h UT, albeit not found in recent radio results), and a tricky visual shower, the Sextantids. Their maximum is expected on September 27, 16h UT, but may possibly occur a day earlier. In 1999 a strong return was detected at λ ~ 186°, equivalent to 2006 September 29, while in 2002, the September 27 peak was not found, but one around September 29 —30 was! There is currently some debate over whether several minor maxima in early October may also be due to this radio shower. The waxing crescent Moon at least creates no additional difficulties for visual observers hoping to catch some Sextantids in late September, tricky enough with radiant-rise less than an hour before dawn in either hemisphere anyway.
Piscis Austrinids and Aquarid/Capricornid Complex
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 (page 23);
v∞ = 35 km/s; r = 3.2;
TFC: α = 255° to 000°, δ = 00° to +15°,
choose pairs separated by about 30° in α (β < 30° N).
Southern δ-Aquarids (SDA)
Active: July 12 —August 19; Maximum: July 28 (λ = 125°); ZHR = 20;
Radiant: α = 339°, δ = -16°; Radiant drift: see Table 6 (page 23);
v∞ = 41 km/s; r = 3.2;
TFC: α = 255° to 000°, δ = 00° to +15°,
choose pairs separated by about 30° in α (β < 40° N).
α-Capricornids (CAP)
Active: Jul 3 —August 15; Maximum: July 30 (λ = 127°); ZHR = 4;
Radiant: α = 307°, δ = -10°; Radiant drift: see Table 6 (page 23);
v∞ = 23 km/s; r = 2.5;
TFC: α = 255° to 000°, δ = 00° to +15°,
choose pairs separated by about 30° in α (β < 40° N);
PFC: α = 300°, δ = +10° (β > 45° N),
α = 320°, δ = -05° (β 0° to 45° N),
α = 300°, δ = -25° (β < 0°).
Southern ι-Aquarids (SIA)
Active: July 25 —August 15; Maximum: August 4 (λ = 132°); ZHR = 2;
Radiant: α = 334°, δ = -15°; Radiant drift: see Table 6 (page 23);
v∞ = 34 km/s; r = 2.9;
TFC: α = 255° to 000°, δ = 00° to +15°,
choose pairs separated by about 30° in α (β < 30° N).
Northern ι-Aquarids (NIA)
Active: August 11 —31; Maximum: August 20 (λ = 147°); ZHR = 3;
Radiant: α = 327°, δ = -06°; Radiant drift: see Table 6 (page 23);
v∞ = 31 km/s; r = 3.2;
TFC: α = 255° to 000°, δ = 00° to +15°,
choose pairs of fields separated by about 30° in α (β < 30° N).
A new ten-year visual analysis of the Aquarid streams and the α-Capricornids was published by Audrius Dubietis and Rainer Arlt in the 2004 June issue of the IMO‘s journal WGN (32:3, pp. 69 —76), coupled with a video radiant analysis from 2002 by Y. and T. Shigeno in the same issue (pp. 77 —80). This generally confirmed the SDA and CAP maxima as falling around July 28 —30 and July 30 —31, with ZHRs of around 15 and 5 respectively. The SIA and NIA did not appear at all clearly, unsurprising given their borderline-visible ZHRs, but the greatest oddity was the NDA, for which no distinct maximum could be traced. Their ZHRs were never better than ~ 3. There were also only weak signs of a vague possible radiant for this source in the Japanese video evidence. All this suggests the NDA may be a good deal less active than previously thought, and may not be producing a visually definable maximum at present. The shower parameters have not been amended as a result of these fresh findings, as there was relatively little difference to those established previously for the better sources. Observers should be alert to the fact that SDA and CAP rates may be near their best beyond the single-date maxima listed however, and that the highest ZHRs may be slightly different to those given as well.
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The PAU were not studied in this latest work, but together with the Aquarid showers, these are all streams rich in faint meteors, making them well-suited to telescopic work, although enough brighter members exist to make visual and photographic observations worth the effort too, primarily from more southerly sites. Radio work can be used to pick up the SDA especially, as the most active source, and indeed the shower can sometimes give a surprisingly strong radio signature. The CAP are noted for their bright — at times fireball-class — events, which, combined with their low apparent velocity, can make some of these objects among the most impressive and attractive an observer could wish for. A minor enhancement of CAP ZHRs to ~ 10 was noted in 1995 by European IMO observers, although the SDA were the only one of these streams previously suspected of occasional variability.
Such a concentration of radiants in a small area of sky makes for problems in accurate shower association. Visual watchers in particular should plot all potential stream members, rather than trying to make shower associations in the field. The only exception is when the SDA are near their peak, as from southern hemisphere sites in particular, rates may become too high for accurate plotting.
All these radiants are above the horizon for much of the night, so only those with expected peaks close to full Moon really lose out. In 2006, late July’s new Moon favours the PAU, SDA and CAP maxima, while the waxing gibbous Moon will still allow some watching for the SIA in early August. The NDA are the main lunar casualty, since August’s new Moon improves the chances for covering the NIA later. Although not confirmed more recently, the NIA showed an ill-defined maximum between λ = 148° —151° in 1988 —95 results, which could mean their better rates (even so, very weak) happen several days after the suspected peak on August 20. If so, those would be still more Moon-free.
κ-Cygnids (KCG)
Active: August 3 —25; Maximum: August 18 (λ = 145°); ZHR = 3;
Radiant: α = 286°, δ = +59°; Radiant drift: see Table 6 (page 23);
v∞ = 25 km/s; r = 3.0;
PFC: α = 330°, δ = +60° and α = 300°, δ = +30° (β > 20° N).
Although rising around midnight, the waning crescent Moon should create few problems for viewing the expected κ-Cygnid peak this year, from the northern hemisphere sites where the shower is chiefly accessible. The r-value suggests telescopic and video observers may benefit from the shower’s presence, but visual and photographic workers should note that occasional slow fireballs from this source have been reported too. The 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 needed on a shower that is often ignored in favour of the major Perseids during August.
Aurigids
α-Aurigids (AUR)
Active: August 25 —September 8; Maximum: September 1, 6h30m UT (λ = 158°6); ZHR = 7;
Radiant: α = 84°, δ = +42°; Radiant drift: see Table 6 (page 23);
v∞ = 66 km/s; r = 2.6;
TFC: α = 052°, δ = +60°; α = 043°, δ = +39° and α = 023°, δ = +41° (β > 10° S).
This essentially northern hemisphere shower appears to be part of a series of poorly observed sources with radiants in Aries, Perseus, Cassiopeia and Auriga, active from late August into October. British and Italian observers independently reported a possible new radiant in Aries during late August 1997 for example. Both this shower and the similarly located δ-Aurigids have recently been investigated by analysts Audrius Dubietis and Rainer Arlt, using IMO-standard data since 1986, and their known parameters updated accordingly.
Of these two detected sources, the α-Aurigids are the more active, with short unexpected bursts having given EZHRs of ~ 30 —40 in 1935, 1986 and 1994, although they have not been monitored regularly until very recently, so other outbursts may have been missed. Only three watchers in total covered the 1986 and 1994 outbursts, for instance!
The δ-Aurigids probably represent a combination of two separate, but possibly related, minor sources, the September Perseids and δ-Aurigids, whose activities and radiants effectively overlap one another. The showers are not resolvable by visual watchers, who are advised to apply the parameters listed in the Working List (Table 5 below), although these primarily derive from the “September Perseid” phase. The “δ-Aurigid” phase seems to give a weak maximum around λ = 181° (2006 September 24; {rm ZHR} ~ 3, r = 2.5).
The radiants in and near Auriga reach useful elevations after 23h —0h local time. Consequently, the α-Aurigid peak on September 1 is favoured over the main δ-Aurigid one, as the waxing Moon then sets well before this time. Conditions will be still more favourable for the δ-Aurigids’ possible September 24 peak, with a waxing crescent Moon. Telescopic data to examine all the radiants in this region of sky — and possibly observe the telescopic β-Cassiopeids simultaneously — would be especially valuable, but photographs, video records and visual plotting would be welcomed too.
Piscids (SPI)
Active: September 1 —30; Maximum: September 20 (λ = 177°); ZHR = 3;
Radiant: α = 005°, δ = -01°; Radiant drift: see Table 6 (page 23);
v∞ = 26 km/s; r = 3.0;
TFC: α = 340° to 020°, δ = -15° to +15°,
choose pairs of fields separated by about 30° in α (β any).
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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 —99 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, September’s new Moon promises perfect observing conditions. Telescopic and video techniques can be usefully employed to study the Piscids, along with methodical visual plotting.