Meteor Activity Outlook for September 19-25, 2009

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. During the second half of the
month the antihelion radiant becomes entangled with the two Taurid radiants and
it is impossible to separate them. Therefore the antihelion radiant will be excluded
from the list from the second half of September 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 progresses from its
new phase (Sep. 18) to nearly half illuminated. This weekend the very thin waxing
crescent moon sets early in the evening and will not interfere with observing. As
the week progresses the moon sets later each night but will still set before the
active morning hours arrive. The estimated total hourly rates for evening observers
this week is near four as seen from the northern hemisphere and two from the
southern hemisphere. For morning observers the estimated total hourly rates should
be near seventeen from the northern hemisphere and seven as seen from the southern
hemisphere. 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.

The radiant positions and rates listed below are exact
for Saturday night/Sunday morning September 19/20. 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:

Recent video studies by Sirko Molau have revealed that activity from the Southern
Taurids (STA) is actually detectable beginning on September 7th. So for now until
December 10th, the Taurid radiants will replace the Antihelion source since they
overlap. The large Southern Taurid radiant is now centered at 00:56 (014) +05. This
area of the sky lies in southern Pisces, three degrees southeast of the fourth
magnitude Delta Piscium. The radiant is large so that any meteor from Pisces, northern
Cetus, northeastern Aquarius, or southwestern Pegasus could be a candidate for this
shower. This radiant is best placed near 0200 LDT when it lies on the meridian and
is located highest in the sky. Maximum activity is not until October 10th so current
rates should be near three no matter your location. With an entry velocity of 29 km/sec.,
the average Southern Taurid meteor would be of medium-slow speed.

The same study of video radiants by Molau has revealed a radiant in Eridanus active
from September 3rd through the 23rd. Maximum activity occurred on September 6th.
The Nu Eridanid (NUE) radiant is currently located at 05:00 (075) +07. This
position is located in western Orion, two degrees east of the fourth magnitude star
known as Pi 3 Orionis. The radiant is best placed near 06:00 LDT when it lies highest
in the sky. Hourly rates are expected to be near one, no matter your location. At
68 km/sec., these meteors are swift with the brightest members often exhibiting
persistent trains.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are
becoming more active. One would expect to see approximately fourteen random meteors
during the last hour before dawn from rural observing sites and three per hour
during the evening hours. As seen from the mid-southern hemisphere (45S) morning
rates would be near four per hour as seen from rural observing sites and one
per hour during the evening hours. Locations between these two extremes would see
activity between the listed figures.

The table below presents a summary of the expected activity this week. Rates and
positions are exact for Saturday night/Sunday morning September 19/20, but may be
used all week.