(meteorobs) Meteor Activity Outlook for August 29-September 4, 2009

Robert Lunsford lunro.imo.usa at cox.net
Fri Aug 28 13:40:45 EDT 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 reaches its full phase on Friday September 4th.
At that time the moon will rise at sunset and will be in the sky the entire
night. This weekend, the waxing gibbous moon will set during the early
morning hours allowing a few hours of dark skies before the start of morning
twilight. This window of opportunity will lessen each night as the week
progresses. The estimated total hourly rates for evening observers this week
is near three as seen from the northern hemisphere and two from the southern
hemisphere. For morning observers the estimated total hourly rates should be
near sixteen from the northern hemisphere and eight 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. Evening rates are reduced by
moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning August 29/30. 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 large Antihelion (ANT) radiant is now centered at 23:16 (349) -03. This
area of the sky lies on the Pisces/Aquarius border, two degrees northeast of
the fourth magnitude Phi Aquarii. Actually, the radiant is so large that any
meteor from northeastern Aquarius, western Pisces, 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 highest in the sky. Rates at this
time should be near two no matter your location. With an entry velocity of
30 km/sec., the average Antihelion meteor would be of medium-slow speed.

The Aurigids (AUR) reach maximum activity on the morning of September 1st.
The redefined radiant, obtained from recent video data and the 2007
outburst, is located near 06:06 (091.5) +39. This position is located in
eastern Auriga, two degrees north of the third magnitude star Theta Aurigae.
The radiant is best placed during the last dark hour before morning twilight
when it lies highest in the sky. Hourly rates on Tuesday morning are
expected to be near five. At 65 km/sec., these meteors are swift, 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 thirteen random
meteors during the last hour before dawn from rural observing sites and two
per hour during the evening hours. As seen from the mid-southern hemisphere
(45S) morning rates would be near six 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. Evening rates are
reduced by moonlight.

The list below presents a summary of the expected activity this week. Rates
and positions are exact for Saturday night/Sunday morning August 29/30, but
may be used all week.

Antihelion (ANT) - 23:16 (349) -03  Velocity - 30km/sec.
Northern Hemisphere - 2 per hr. Southern Hemisphere - 2 per hr.

Aurigids (AUR) - 06:06 (091.5) +39  Velocity - 65km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - <1 per hr.

     *For a detailed explanation on the different classes of meteor showers 
and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2009

Clear Skies!
Robert Lunsford
American Meteor Society




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