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(meteorobs) Meteor Activity Outlook for Aug. 24-30, 2001



The moon reaches its first quarter phase on Saturday August 25th.  The
evening sky will have interference from moonlight late during this
entire period. The late morning sky is still free of moonlight but with
each passing day this dark period becomes less. The estimated total
hourly rates for evening observers this week should be near 2 for those
in the Northern Hemisphere and 1 for those in the Southern Hemisphere.
For morning observers the estimated total hourly rates should be near 15
for the Northern Hemisphere and 7 for those located in 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 for meteor
activity. The positions listed below are exact for Saturday night/Sunday
morning August 25/26. The positions do not change greatly day to day so 
these positions may be used during this entire period.

The Kappa Cygnids can provide some low activity to the evening skies and
on into morning. The radiant position lies at 19:12 (288) +60 which
actually places it in Draco 6 degrees north of Kappa Cygni. The Kappa 
Cygnids seem temperamental and are either non-existent or quite active.
The expected rates are 1 per hour during the evening hours decreasing
later on during the morning as the radiant sinks into the northwest.
Activity is possible all night long as seen from the Northern
Hemisphere. Very low activity is possible for observers between 30
degrees south and the equator during the evening hours. This shower is
invisible south of 30 degrees south latitude. The shower members are
very slow and often bright with vivid colors. There have been reports of
fragmenting Kappa Cygnids as they slowing fall through the sky. 

The North Iota Aquarid radiant reached maximum activity on August 19.
Rates will vary from 2 per hour as seen from the Southern Hemisphere to
less than 1 per hour from the high Northern Hemisphere. The current 
radiant position lies at 22:12 (333) -05. This position lies in central
Aquarius 3 degrees north of the 5th magnitude star Theta Aquarii. They
are best seen near 0100 local daylight time (0000 local standard time) 
when it lies highest in the sky. These meteors are slow regardless where
they appear in the sky.

The Antihelion radiant is now located at 23:08 (347) -05. This area of
the sky is located in eastern Aquarius near the 5th magnitude star 90
Aquarii. Any slow to medium speed meteor from the eastern half Aquarius
or western Pisces may be a good candidate for this shower. This position
is also only 3 degrees from the center of the North Delta Aquarid
radiant making the two radiant virtually indistinguishable. It would be
best at this time to label all meteors from this area ANT as the NDA's
are less likely to produce any activity. This area of the sky is best
placed near 0200 local daylight time (0100 local standard time) when it
lies on the meridian. At this time expect to see perhaps 2 per hour from
all locations. Unlike most of the annual showers the antihelion radiant
is produced by debris from unknown sources orbiting in a direct motion
like the earth. These sources are most likely asteroids, which produce
stony and metallic debris whose density is much greater that produced by 
comets. This debris collides with the earth on the inbound portion of
its orbit, before its closest approach to the sun. Therefore we best see
them just after midnight when we are facing the direction from which
this activity appears. The antihelion radiant is active all year from an
area of the sky nearly opposite that of the sun. The radiant will travel
approximately one degree eastward per day and travels through many
different constellations over the course of a year.

The North Delta Aquarids are now nearing the end of their activity.
Rates are now less than 1 per hour and will soon stop completely. The
radiant is currently located at 23:12 (348) -02. This area of the sky is
located in western Pisces 5 degrees south of Gamma Piscium and very
close to the antihelion radiant. The radiant is best placed between 0200
and 0300 LDT or 0100 to 0200 local standard time when it is located
highest in the southern sky. At this time expect to see less than 1 true
NDA per hour. A majority of the activity from this region would belong
to the antihelion radiant. These meteors are of average velocity.

The Pi Eridanids reach maximum activity on August 27 with a predicted
ZHR of 4. Actual rates would more likely be 1 per hour unless you live
near the equator where the radiant passes overhead. The radiant position
is located at 03:24 (051) -15, which places it western Eridanus 5
degrees south 4th magnitude star Epsilon Eridani. This area of the sky
is better placed for observers in the north tropical zone and areas
further south. It lies highest in the sky just before the onset on dawn.
Like the Perseids these meteors are swift if seen high in the sky far
from the radiant. I would also expect some trains from the brighter
shower members.

The Gamma Doradids are listed among the DMS radiants. The radiant
position lies at 03:56 (059) -51, which places on the Eridanus/Dorado
border 3 degrees west of the 4th magnitude star Gamma Doradus. Many of
you may have not heard of these far southern constellations which lie
some 50 degrees southwest of the well known constellation of Orion.
Obviously this radiant is best seen from the Southern Hemisphere. Some
activity may be glimpsed from the northern tropical areas just before
dawn. The date of maximum activity is August 30 so current rates may be
1-2 per hour as seen from the Southern Hemisphere. Shower members
possess an average velocity of 41 km/sec., similar to the Delta Aquarid
radiants.

The Northern Apex radiant is now located at 04:08 (062) +36. This
position lies in southeastern Perseus some 2 degrees east of the 4th
magnitude star 46 Persei. This area of the sky is best placed for
viewing during the last dark hour before dawn. Since this radiant is
diffuse any meteors from southeastern Perseus, northwestern Taurus, or
western Auriga could be a good candidate. As seen from the Northern
Hemisphere this source should produce at least 3 meteors per hour during
the last few hours before dawn. Rates seen from the Southern Hemisphere
would be much less at 0-1 per hour. 

Like the antihelion radiant both apex radiants are active all year long
and travel approximately one degree eastward per day. Unlike the
antihelion debris these particles orbit the sun in a retrograde motion
opposite that of the earth and are most likely produced by unknown
comets. They strike the earth after their closest approach to the sun.
Since they are moving in opposite directions these particles strike the
earth at tremendous velocities often creating bright meteors with
persistent trains. These particles strike the earth on the morning side
of earth and are best seen just before morning twilight while the sky is
still perfectly dark. There are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90
degrees west of the sun. These meteors are rare though as the earth
orbits the sun it "sweeps clean" much of the material that shares the
same orbit. Much more debris is located just north and south of the
earth's orbit with slightly higher or lower inclinations. This creates
the northern and southern branches of the apex activity. Meteors from
both branches are normally included in the sporadic count but should
also be noted in some manner as to which branch of the apex complex they
appear to radiate.

The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 04:08 (062) +06. This position lies in southwestern
Taurus 2 degrees east of the 4th magnitude star Nu Tauri. Like the
northern apex these meteors are best seen toward dawn when the radiant
lies highest above the horizon in a dark sky. Any meteor from
southwestern Taurus, extreme northern Eridanus, or  western Orion could
be a candidate from this source. Rates should be close to 2 per hour
from most locations.

The Sporadic rates for the Northern Hemisphere are now near 7 meteors
per hour during the last hours before dawn from rural observing sites.
This estimate and the morning estimate for the Southern Hemisphere does
not include the apex meteors listed above. During the evening hours
perhaps 2 random meteors can be seen per hour from the Northern
Hemisphere. Rates seen from the Southern Hemisphere are now declining
with perhaps 4 random meteors being seen per hour during the late
morning hours and 1 per hour during the evening. Moonlight interferes
with evening viewing as seen from both hemispheres.

Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator
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