British Astronomical Association
	Meteor Section

2004 Perseids

Having been adversely affected by strong moonlight at their maximum in 2003, the 2004 Perseids were keenly anticipated by Meteor Section observers, hoping for high activity in dark skies: the Moon would be New on 15 August, meaning that only a thin, late-rising crescent would affect conditions close to the shower’s 12-13 August peak. The previous well-observed return, in 2002, produced the usual strong Perseid maximum, with sky- and radiant altitude-corrected Zenithal Hourly Rate (ZHR) of the order of 80 on 12-13 Aug, but no indication of unusual activity was seen: between 1988 and 1996 (and especially in 1993-4), additional strong early peaks had been noted in association with the 1992 perihelion of the Perseids’ parent, Comet 109P/Swift-Tuttle.

Ahead of the 2004 return came some interesting predictions, based on computer modelling of the Perseid meteor stream, from Esko Lyytinen and Tom Van Flandern. This work suggested that recently-ejected material from the parent comet might produce enhanced activity of faint Perseids around Aug 11d 21h UT, while a resonance effect with Jupiter might also lead to enhanced Perseid rates later in the night of 11-12 Aug. The regular annual peak at Solar longitude(2000.0) = 140.0o was expected around mid-day on 12 August, meaning that observers in western Europe might expect best rates late on 11-12 Aug and early on 12-13 Aug, with activity gradually declining on the latter night.

The summer of 2004 will be less than fondly remembered by most in the British Isles, as cloudy and wet! Conditions really were very poor for the Perseids, and the volume of observations received by the BAA Meteor Section has suffered in consequence. Visual reports totalling 70h 52m watch time for a much lower-than-normal total of 1150 meteors (245 sporadics, 891 Perseids and 34 others) were received, covering the interval from 6-7 to 16-17 August. Observers are listed below:

Visual: S Beaumont, N Bone, G Boots, D Chippendale, M Coupar, J Dawson, L Entwisle, D Gavine, M Green, W Greer, C Hall, A Heath, R Johnson, T Lloyd Evans, H McGee, T Markham, J Marshall, R Marshall, C Potter, J Shepherd, M Stephens, D Storey, L Storey, D Swain, A Vincent, P Yates

Radio: A Heath, N Quinn

Video: L Entwisle, S Evans, W Greer, A Pratt

If anything, best conditions in the UK were found over the weekend of 6-7 and 7-8 August, at which time the Moon restricted productive watches to the earlier parts of the night when the Perseid radiant was still low. ZHR ion the range 15-20 was found, with observed rates still rather low. Some UK-based observers were luckier on 10-11 August, although patchy cloud was still a problem on this night - by which time the ZHR was starting its climb towards maximum, having reached about 45.

August 11-12 was very poor weatherwise over the UK. Dave Gavine and Jamie Shepherd had some success from southern Scotland: after much driving in pursuit of gaps in the overcast, their three hours’ total watch time netted 8 sporadics and 143 Perseids, including a magnificent flaring mag. -8 Perseid with a 45-second train at Aug 12d 01h 47m UT. The bulk of coverage for this night comes from members based in mainland Europe. Callum Potter and Michael Stephens have provided valuable data from southern France, while Bill Greer has submitted counts based on video and visual observations from Spain. Activity was respectable in early evening, with ZHR 40-60 around 23h UT. Low radiant elevation makes reliable determination of ZHR around the critical 21h UT timepoint difficult. ZHR was perhaps as high as 90-120 in the early morning hours.

High observed rates were reported between 0216-0316 UT by Michael Stephens (58 Perseids in LM 4.5 skies with occasionally-extensive patchy cloud).

Reports elsewhere, from the International Meteor Organisation, suggest that the strong early peak did occur, while Perseid activity was indeed elevated throughout the early morning hours of 12 August.

The wet weather of the previous 24 hours began to clear eastwards from the UK on 12-13 August, and observers in the west of the country had some decent skies on this night. Activity does seem to have been lower than on 11-12 August, though there is a fair amount of scatter in the reductions; ZHRs between 50-95 are found from reports by experienced observers. Steve Evans at Moreton-in-Marsh, Glos., ran his low-light video system (EMILY), recording 102 meteors (74 Perseids, 20 sporadics and 8 others, to a limiting magnitude of +3.5) on this night.

By 13-14 Aug, when observers in Scotland and the north of England had some reasonable skies, activity had certainly fallen back, to ZHR perhaps 20-25.

Results are summarised in the rates-curve below; the very high point on Aug 11-12 is probably spurious!
 

Relatively few very bright events were seen over the shower as a whole. From observers’ estimates, mean Perseid magnitude is +1.33 relative to +2.24 for sporadics in the same interval - values very much in keeping with recent previous years. Persistent trains were reported for 30.6% of Perseids compared with 12.2% of sporadics, again consistent with past results.
 

Page last updated: 01/09/2005