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BAA electronic circular No. 00126
www.britastro.org/
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Observing Opportunity - 2003 Geminid meteors
In common with all the other major showers since last January's
Quadrantids, the 2003 Geminids - active from December 7 to 16 - are
adversely affected by strong moonlight. Observers may, however, wish to
take advantage of the brief windows of early-evening dark sky available
close to maximum on Dec 13-14 and 14-15, when Geminid rates could still
be worthwhile despite a low radiant elevation.
Geminid maximum is expected around 10h UT on the Sunday morning of
December 14. The peak has been found, in recent years, to be broad, and
high activity can be expected for perhaps 18 hours to either side of
this time. Watches in the early evening of Saturday-Sunday Dec 13-14
should catch the Geminids climbing towards maximum, but will be
restricted by an early-rising waning gibbous Moon whose glare will swamp
the fainter meteors after about 20h local time.
Observed rates may actually be better early on the Sunday-Monday of
December 14-15, by which time moonrise has moved back to about 21h local
time. Bright Geminids could be more abundant on this night too: past
observations show these to predominate in the interval just after the
highest rates occur.
The Geminid radiant at RA 07h 32m Dec +33o is just north of
Castor, and is above the horizon all night from UK latitudes in
mid-December. It will, however, be comparatively low in the northeastern
sky in early evening, not attaining an elevation of 30 degrees until
moonrise on Dec 14-15. Low radiant elevation will peg observed rates
back somewhat. Given clear, dark skies, observers might hope to log
upwards of 20 Geminids/hr before moonrise on Dec 13-14 and 14-15 -
welcoming leavening in what has thus far been a rather thin year for
regular meteor-watchers.
The Geminids are unique among the major annual showers in that
their parent body is an asteroid - (3200) Phaethon - rather than a
comet. Consequently, the meteoroids appear to be relatively robust,
penetrating to lower altitudes in Earth's atmosphere than those from,
say, the Perseid or Orionid streams. Geminids are slow (geocentric
velocity 35 km/s) and the brighter meteors can be long-lasting - factors
which make the shower an attractive photographic target. Photographers
hoping to catch Geminids on film could try time exposures (10-15
minutes) at f/2 top f/2.8 with standard or wide-angle lenses and ISO 400
film, aiming in the direction of Taurus in early evening.
Observations by the Meteor Section's standard methods (outlined at
http://www.britastro..com/meteor) will be welcomed by the Director.
While moonlight will rather limit our view of the Geminids this time
around, prospects could hardly be better for the 2004 return 12 months
hence! Observers are also reminded that we need coverage of the Ursids
(active Dec 17-25, peak Dec 22-23), which will be the subject of a later
e-circular.
Neil Bone
Director, BAA Meteor Section
  