The year opened with very unfavourable conditions (a Full Moon!) for the Quadrantids in early January. In the coming months, however,  there are plenty of good observing opportunities -  looking ahead to the autumn, especially, the Orionid, Leonids and Geminids will each be well-placed for dark sky conditions. In the more immediate future, the Lyrids offer a chance to clock up some observing time with reasonable activity following the quiet months of the year’s opening quarter. Come high summer, the August’s Perseids are superbly-placed in 2007

Lyrids
Active April 19-25
Radiant RA 18h 08m Dec +32°
Many observes look on April’s Lyrid shower as bringing to a close the rather barren period for meteor activity that prevails during the late winter/early spring. The shower, while relatively modest, brings a welcome upturn in rates for a few nights, particularly around the maximum – expected late on the evening of April 22-23 (a Sunday night to Monday morning) – normally producing observed rates of perhaps
6-8 meteors/hr under the clearest and darkest conditions when the radiant is well up in the sky, corresponding to corrected Zenithal Hourly Rate (ZHR) around 10. Activity is about this level for 12 hours or so centred on the maximum. At other times, observed Lyrid rates may be only 2-3 meteors/hr – still worthwhile, coupled with similar background sporadic meteor activity, for regular observers.
      Best observed Lyrid rates will typically be found after midnight UT, and the radiant (some 10o southwest of Vega, near the Lyra/Hercules border) climbs higher in the sky. Radiant elevations are given below:

Local Time (53oN)    Radiant Altitude       Local Time   Radiant Altitude
21h                                       16.2°                      01h                      50.9°
22h                                       24.2°                      02h                      59.3°
23h                                       32.9°                      03h                      66.0°
00h                                       41.9°                    

On April 22-23, the Moon will be a 5-day waxing crescent, setting in the northwestern sky after 01h local time. Its glare will present some distraction early in the night, but with observers ideally directing their fields of view to the east, lunar interference should be minimal, and darker skies will be found in the interval just before dawn.
      The Lyrids are produced by debris from Comet C/1861G1 Thatcher. The incoming meteoroids have atmospheric entry velocities  of 49 km/s, and Lyrid meteors appear swift. A fair proportion are bright, and leave persistent ionisation trains. .As a result of poor weather, relatively few observations were received in 2006, but there are suggestions that last year’s return was graced by a higher-than-usual abundance of bright Lyrids.
      On a few past occasions, activity has also been markedly higher than normal – most recently in 1982 when, for a couple of hours, ZHR around 200 was attained. While there is no expectation of enhanced activity in 2007, the Lyrids have sprung surprises on us in the past, and remain a shower very much worth observing.


Alpha Scorpiids
Active April 20-May 19
Radiant   RA 16h 31m Dec -24°
               RA 16h 04m Dec -24°
Ophiuchids
Active May 19-early July
Radiant  RA 17h 56m Dec -23°
              RA 17h 20m Dec -20°
Present more-or-less year-long is a steady trickle of meteor activity emanating from diffuse, multiple radiants close to the ecliptic plane. During late spring and into early summer, this manifests as the weak Alpha Scorpiid and Ophiuchid showers from radiants low in the southern sky as far as UK-based observers are concerned. Observations are rendered difficult by the twilit conditions that prevail throughout the short nights at the latitudes of the British Isles during this interval. Patient, determined observers may, however, record rates of one or two meteors/hr from these sources. These meteors are typically slow, and with radiants low over the horizon can sometimes have near-grazing atmospheric trajectories and relatively long paths across the sky.


Alpha Capricornids
Active July 15- August 20
Radiant  RA 20h 36m Dec  -10°
Delta Aquarids
Active July 15-August 20
Radiants N RA 23h 04m Dec +02°
               S  RA 22h 36m Dec -17°
With Full Moon falling on July 30, unfavourably bright skies will meet the most active periods of the Alpha Capricornids and Delta Aquarids, showers whose radiants lie below the Square of Pegasus. The Delta Aquarids’ southern branch is the more active, peaking around July 27. The Alpha Capricornids reach maximum around August 2, at which time the early-rising Moon will still be a considerable nuisance. Observers will, of course, record a few meteors from these showers (and the Capricornids and Iota Aquarids) during watches for the Perseids – see below – in early August.  Alpha Capricornids tend to be long and slow, and sometimes bright. Delta Aquarids are medium-paced meteors, mostly in the magnitude +1 to +4 range.


Alpha Cygnids
Active July-August
Radiant RA 21h 00m Dec +48°
For much of the northern summer, observers record a steady trickle of activity from an apparently stationary radiant near Deneb in Cygnus. Observed rates are typically one or two per hour, and there are some doubts as to whether this is a genuine shower: most showers, as a result of Earth’s orbital motion around the Sun, show an eastwards radiant motion of about a degree per day, and stationary radiants are therefore viewed with some suspicion!



Perseids
Active July 23-August 20
Radiant RA 03h 04m Dec +58°
The undoubted stand-out for meteor observers in the summer of 2007 is a very favourable return of the Perseids, peaking on Aug 13d 02h UT in dark, moonless skies. At this time, just as dawn is approaching for observers in the British Isles, the Perseid radiant will be high in the eastern sky and from locations away from artificial light pollution rates of around a meteor per minute should be attained. In most years, the Perseids produce corrected ZHR around 80 at maximum, with rates at half that level on Aug 11-12 and 13-14. Indeed, watches on any night in the 10-day interval centred on Perseid maximum are likely to be very productive for the patient observer: this is a great time for new observers to try their hand at meteor work! All else being equal, best rates are found when the Perseid radiant – near the ‘Sword Handle’ on the Perseus-Cassiopeia border – is highest in the sky during the pre-dawn hours. Even in early evening, however, the radiant is already quite favourably placed:

Local Time (53oN)   Radiant Altitude     Local Time    Radiant Altitude
21h                             28.1°                                     01h                  52.8°
22h                             32.8°                                     02h                  59.3°
23h                             38.4°                                     03h                  67.1°
00h                             44.7°

Observers should bear in mind the nightly eastwards ‘drift’ of the Perseid radiant e to Earth’s orbital motion. In early August, the radiant is 15 degrees west of its position at maximum (given above), to the north of Andromeda.
    New Moon falls on August 12, and the Perseid maximum night of Aug 12-13 (a Sunday to Monday) will be free from lunar interference. Productive watches become possible from about Aug 6-7 onwards, with the waning crescent Moon retreating into the morning sky and rising later from night to night.
     Perseid meteors are produced by debris from Comet 109P/Swift-Tuttle. Incoming meteoroids have atmospheric entry velocities of 60 km/s, resulting in very fast meteors. A healthy proportion of Perseids are bright, making the shower a good target for photography. Perseids brighter than about magnitude 0 can be captured at film speeds of ISO 400 or greater with a camera fitted with either a 50 mm standard lens or 28 mm wideangle lens at f/2.8 or faster, using time exposures aimed towards Cygnus or the Square of Pegasus. These need not be driven – ‘static’ cameras yield images with meteors appearing as longer streaks cutting across the short arcs of star trails. Users of conventional film can try exposures of 10-15 minutes’ duration. Some observers enjoyed success with digital exposures of 30 seconds’ duration in 2005: obviously, these demand availability of sufficient memory as a night’s operation may amount to as many as 500 images!
      Being fast meteors, Perseids – particularly the brighter examples – often leave behind persistent ionisation trains.
      As one of the year’s most consistent very active showers (alongside the Quadrantids and Geminids), the Perseids justifiably enjoy favour with even casual observers. The 2005 return was well-observed from the UK, showing a typical strong peak with ZHR 70-80 and the usual abundance of bright events. It appears that the enhanced Perseid activity attending the 1992 perihelion return of the parent comet is now behind us, but the shower’s regular, fairly dependable performance makes this a continued highlight of the meteor observer’s year. Circumstances of the shower could hardly be more favourable for the UK in 2007, both in terms of the absence of moonlight, and the timing of maximum: observers should make the most of this opportunity – moonlight will severely restrict viewing in 2008.
   

Observations of these, and other less-active showers, together with sporadic activity, will be welcomed by the Meteor Section. Observing instructions can be found on the website at http://www.britastro.org/meteor
Send reports and enquiries to the Meteor Section Director:

Neil Bone, ‘The Harepath’, Mile End Lane, Apuldram, Chichester, West Sussex, PO20 7DZ
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