(meteorobs) Meteor Activity Outlook for September 21-27, 2007

Robert Lunsford lunro.imo.usa at cox.net
Sat Sep 22 21:42:02 EDT 2007

September offers longer nights and cooler temperatures in the northern
hemisphere. In the sky no major showers are visible from either hemisphere
but the northern hemisphere enjoys the advantage of higher sporadic rates.
The two recognized minor showers active in early September have high
northern declinations (celestial latitude) therefore are much better suited
to be viewed from locations north of the equator. Toward the end of the
month the antihelion radiant becomes entangled with the two Taurid radiants
and is impossible to separate. Therefore the antihelion radiant will be
excluded from the list until the end of the Taurid activity period late in
November. Observers in the southern hemisphere suffer from some of their
lowest rates of the year this month. The Taurid radiants are not too badly
placed so observers south of the equator can expect to see a little of this
activity toward the end of the month.

During this period the moon reaches its full phase on Wednesday September
26. At this time the moon is located opposite the sun and is in the sky all
night long. This weekend a small window of opportunity exists between
moonset and the start of morning twilight. The estimated total hourly rates
for evening observers this week is near three for those located north of the
equator and one for observers south of the equator. For morning observers
the estimated total hourly rates should be near ten for those located in the
northern hemisphere and five for those viewing from south of the equator.
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 due
to moonlight during this period.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning September 22/23. 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 following showers are expected to be active this week:

The Antihelion (ANT) radiant is now centered at 00:52 (013) +06. This area
of the sky is located in a southern Pisces just one degree south of the
fourth magnitude star Delta Piscium. This radiant is best placed near 0200
LDT, when it lies on the meridian and is highest in the sky. Rates at this
time should be near two per hour regardless of your location. With an entry
velocity of 30 km/sec., the average antihelion meteor would be of
medium-slow speed.

The Delta Aurigids (DAU) are present in the morning skies in the second half
of September and early October. Maximum activity occurs on October 4 with an
average ZHR of two. Current rates will be most likely less than one per
hour. The radiant is located 05:00 (075) +49. This position lies in
northwestern Auriga, four degrees northwest of the zero magnitude star
Capella (Alpha Aurigae). At 64km/sec., the average Delta Aurigid is swift.

Sporadic rates are slowly rising for observers in the northern hemisphere
and falling steadily for those located south of the equator. One would
expect to see approximately eight random meteors during the last hour before
dawn from rural observing sites in the northern hemisphere. During the first
dark hour after the end of evening twilight, perhaps two random meteors can
be seen per hour. As seen from the southern hemisphere late morning rates
would now be near three per hour. During the first dark hour after the end
of evening twilight, perhaps one random meteor can be seen per hour. Rates
are reduced due to moonlight during this period.

Antihelion (ANT) - 00:52 (013) +06 30
Northern Hemisphere - 2   Southern Hemisphere - 2

Delta Aurigids (DAU)  05:00 (075) +49
Northern Hemisphere - <1   Southern Hemisphere - <1

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:

Clear Skies!
Robert Lunsford
American Meteor Society

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