Last quarter Moon spoils the northern-hemisphere Quadrantids, as it will be well above the horizon after midnight, just like the Quadrantid radiant (maximum is due around 12h20m UT on January 3), but the southern-hemisphere α- Centaurids are superbly-placed for new Moon. The minor δ-Cancrids are reasonably moonless, but not so the δ- Leonids, whose February 24 peak coincides with full Moon! The diffuse ecliptical stream complex of the Virginids gets underway by late January, running through to mid April, probably producing several low and poorly observed maxima in March or early April. The interesting late January to early February spell (during which several new, swift-meteor minor showers radiating from the Coma- Leo-Virgo area have been suggested in recent years), is severely moonlit, especially for most of the, perhaps core, January 20-27 period. Mid-March brings more helpful dark skies to check for southern-hemisphere γ-Normid rates. Theoretical approximate timings for the daytime radio shower maxima this quarter are: Capricornids/Sagittarids – February 1, 8h UT; χ-Capricornids – February 13, 9h UT. Recent radio results suggest 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.
δ-Cancrids
Active : January 1-24; Maximum : January 17 (sol = 297°); ZHR : 4; Radiant : alpha = 130°, delta = +20°; Radiant drift: see Table 6; V : 28 km/s r : 3.0; TFC : alpha = 115°, delta = +24° and alpha = 140°, delta = +35° (beta > 40° N); alpha = 120°, delta = -03° and alpha = 140°, delta = -03° (beta < 40° N).
This minor stream of predominantly faint meteors is well-suited to telescopic observations, with a large, complex, diffuse radiant that probably consists of several sub-centres. Visual observers should assume a minimum radiant size of roughly 20° in α by 10° in δ about the radiant point given above. This type of large, loose radiant area is similar to the Virginids, and the δ-Cancrids are probably an early part of the Virginid activity. Recent observations have suggested the peak may occur close to sol = 291° (2005 January 11), though ZHRs do not rise above ~ 3-4 even then. New Moon on January 10 to first quarter on January 17 (moonset even then is around, or soon after, local midnight), means both potential peak times will be nicely moonless, so watches throughout this period to see what occurs should definitely be attempted. The long northern winter nights are ideal for making observations, while the radiant is above the horizon almost all night in either hemisphere.
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Figure 1
– Radiant position of the δ-Cancrids.
α-Centaurids
Active : January 28-February 21; Maximum : February 7, 22h45m UT (sol = 319.319°); ZHR : variable, usually ~ 6, but may reach 25+; Radiant : alpha = 210°, delta = -59°; Radiant drift: see Table 6; V : 56 km/s r : 2.0.
The α-Centaurids are one of the main southern hemisphere high points in the opening months of the year, producing many very bright, even fireball-class, objects (meteors of at least magnitude -3). Their peak ZHR is normally around 5-10, but in 1974, and again in 1980, bursts of only a few hours’ duration yielded activity closer to 20-30. As we have no means of telling when another such event might happen, photographic, video and visual observers are urged to be alert. Thanks to their brilliance, even a normal α-Centaurid return is worth looking out for, with almost one-third of shower meteors leaving persistent trains. The radiant is nearly circumpolar for much of the sub-equatorial inhabited Earth, and is at a useful elevation from late evening onwards. Lunar news is excellent this year, with new Moon on February 8 creating perfect observing conditions.
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Figure 2
– Radiant position of the α-Centaurids.
γ-Normids
Active : February 25-March 22; Maximum : March 13 (sol = 353°); ZHR : 8; Radiant : alpha = 249°, delta = -51°; Radiant drift: see Table 6; V : 56 km/s r : 2.4; TFC : alpha = 225°, delta = -26° and alpha = 215°, delta = -45° (beta < 15° S).
Figure 3
– Radiant position of the γ-Normids.
γ-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+ often 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, and in 1999 independent observations in Australia and South Africa suggested the peak may have fallen on March 17. Post-midnight watching yields best results, when the radiant is rising to a reasonable elevation from southern hemisphere sites (the radiant does not rise for many northerly locations). The shower badly needs more regular observation, and with the new to first quarter Moon spell (March 10-17) covering both possible maximum times, 2005 is an excellent year to make a start. All techniques can be employed.