Meteor Activity Outlook for December 21-27, 2007

No matter where you live, the first half of
December provides some of the best meteor activity of the year. In the northern
hemisphere the sporadic rates are still strong plus you can also count on strong
activity from the Geminids, which peak on December 14. There are also several
minor radiants that add a few meteors each hour. All of these centers of activity
are located high in the sky during the early morning hours this time of year. The
night of December 13/14 is no doubt the best night of the year to view meteor
activity. The moon is favorable during this entire period. After the 15th, the
shower activity suddenly wanes and a great majority of the activity seen is
sporadic. Approaching Christmas the moon become a major factor and ruins the
maximum of the Ursid shower.

As seen from the southern hemisphere the sporadic rates are increasing toward a
January maximum. Shower rates are also good but the Geminids suffer a bit from
the lower elevation seen from southern locations. Still with the warmer weather
now occurring south of the equator, December is a great time to view celestial
fireworks.

During this period the moon reaches its full
phase on Monday December 24. The moon will remain a major factor during this
entire period obscuring all but the brightest meteors. The sources of meteors
listed below are active during this period but will be difficult to observe this
week due to the lunar glare. If your sky is transparent and the limiting magnitude
exceeds +5.0, then you may be able to achieve some success. The estimated total hourly
rates for evening observers this week is two from the northern hemisphere
and one from south of the equator. For morning observers the estimated
total hourly rates should be near seven from the northern hemisphere and
four from the southern hemisphere. These rates assume that you are
watching from rural areas away from all sources of light pollution. The
actual rates will also depend on factors such as personal light and motion
perception, local weather conditions, alertness and experience in watching
meteor activity. Rates are reduced this week due to intense moonlight.

The radiant positions and rates listed below are exact
for Saturday night/Sunday morning December 21/22. These positions do not change
greatly day to day so the listed coordinates may be used during this entire period.
Most star atlases (available at science stores and planetariums) will provide maps
with grid lines of the celestial coordinates so that you may find out exactly where
these positions are located in the sky. A planisphere or computer planetarium program
is also useful in showing the sky at any time of night on any date of the year.
Activity from each radiant is best seen when it is positioned highest in the sky,
either due north or south along the meridian, depending on your latitude. It must
be remembered that meteor activity is rarely seen at the radiant position. Rather
they shoot outwards from the radiant so it is best to center your field of view so
that the radiant lies at the edge and not the center. Viewing there will allow you to
easily trace the path of each meteor back to the radiant (if it is a shower member)
or in another direction if it is a sporadic. Meteor activity is not seen from radiants
that are located below the horizon. The positions below are listed in a west to east
manner in order of right ascension (celestial longitude). The positions listed first
are located further west therefore are accessible earlier in the night while those
listed further down the list rise later in the night.

The full descriptions of each active meteor shower will continue next week when
the moon becomes less of a nuisance to observers. It should be noted that the
Ursids may produce a short outburst near 21UT on the 22nd. This timing favors
Europe, Asia, and the northern polar regions.