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(meteorobs) Meteor Activity for the Week of December 24-31, 1999
The moon has just passed its full phase and is now waning toward last
quarter. This will free up the early evening hours for observing without
lunar interference. Typically at this time of night one would see an
average of 5 sporadic (random) meteors per hour from dark rural
observing sites. Once the moon reaches last quarter on Wednesday,
December 29, the entire evening will be free of moonlight. At this time
it is often asked if it is better to watch before midnight in dark skies
or to endure lunar interference during the morning hours. On most
occasions observers would see more activity during the morning hours
despite the presence of moonlight. Meteor rates are stronger after
midnight and the last quarter moon is much less intense than it is
when near full. This allows rural observers to achieve limiting
magnitudes of 6.0 when facing areas of the sky away from the moon.
Sporadic rates would be near 10 per hour under such conditions so
meaningful data can be obtained despite the presence of moonlight.
For observers limited to watching during the early evening hours, the
only known radiant above the horizon at this time would be the Chi
Orionids. During this week this radiant is located in south-central
Gemini near the position 6:45 +20. The radiant is just below the horizon
at dusk rising higher into the eastern sky as evening progresses. It
reaches the meridian (due south) between midnight and 0100 and is best
situated for viewing at this time. This shower produces meteors of
medium-slow speed with typically 1-2 shower members per hour this time
of year.
The Coma Berenicid activity continues this week with the radiant lying
in western Coma Berenices near the position 12:12 +22. The radiant rises
near midnight therefore no activity can be seen from this shower during
the evening hours. The best rates from this shower will occur just
before dawn when the radiant lies high in the south. The Coma Berenicids
are swift meteors with many persistent trains. The moon is located near
the radiant early next week so be sure to face away from this area,
perhaps toward the north or the southwest to avoid direct moonlight and
the loss of night vision.
During my Geminid observations I happen to notice several swift meteors
each morning coming from an area near the Leo-Virgo border. These
meteors are related to the Apex radiant which lies 90 degrees west of
the sun and produces 1-2 meteors per hour on average. This radiant is
now located in western Virgo near the position 12:30 -3. This is close
to the famous 3rd magnitude double star Porimma or Gamma Virginis. This
radiant also rises near midnight and is best seen just before dawn.
Enhanced Coma Berenicid rates could be due to inclusion of these apex
meteors since the velocities are similar and the radiants are fairly
close in the sky. Once the moon is out of the picture it is suggested to
face a bit more toward these radiants to aid in shower association.
Finally, there have been scattered reports of activity from the
constellation of Lynx during this period. This faint but large
constellation is located in the area between the Big Dipper and Gemini.
Any possible activity from this area would possess medium velocities.
Any confirmation of such activity or lack of activity would be important
in assisting us analyze activity for this particular time period.
Merry Christmas Everyone!
Bob Lunsford
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