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(meteorobs) Meteor Activity Outlook for July 27-Aug 2, 2001

Sorry for the delay this week. There have been computer problems on this
end of the line :(


The moon reaches its first quarter phase on Friday July 27th.  The
evening sky will be saturated with moonlight the entire period. The
morning sky will be free from moonlight early in the period but after
the weekend this window of darkness becomes quite small. The estimated
total hourly rates for evening observers this week should be near 1 for
all observers. These rates are reduced due to moonlight. For morning
observers the estimated total hourly rates should be near 25 for the
Northern Hemisphere and 30 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 July 28/29. The
positions do not change greatly day to day so these positions may be
used during this entire period. 

The Alpha Capricornid radiant is located at 20:24 (306) -10. This area
of the sky is located in extreme northwestern Capricornus just 3 degrees
north of the naked eye double star Alpha Capricorni. This area also lies
in the outer radiant area of the antihelion radiant. Any meteor
traveling east or west out of this area would be difficult to classify.
At this time rates of the Alpha Caps would have slightly better rates
producing 2-3 meteors per hour, depending on the elevation of the
radiant above your horizon. With an entry velocity of 25 km/sec. the
Alpha Caps are just a bit slower than the  Antihelion meteors. The Alpha
Cap radiant is best placed near 0100 local daylight time (0000 local
standard time) when it lies on the meridian. While a majority of the
Alpha Cap activity is faint, this radiant is noted for its colorful
fireballs. 

The Alpha Cygnids are listed as the Psi Cygnids among the radiants of
the Dutch Meteor Society. No matter what you call them they are often
overlooked by the many other better-known radiants active at this time.
This radiant was well represented in the studies coordinated by Peter
Jenniskens between 1980 and 1991. Their studies indicate a ZHR near 3 at
maximum activity on July 18. The current rates would be near 1 per hour
from the Northern Hemisphere. The radiant position is 20:44 (311) +49.
This position is located in northern Cygnus 4 degrees north of the
bright star Deneb (Alpha Cygni). With an entry velocity of 37 kilometers
per second these meteors are of average speed. The radiant is best
placed for observing near 0200 LDT or 0100 local standard time when it
lies nearly overhead for much of the Northern Hemisphere. Due to its
high northern declination this activity is not well seen from the
Southern Hemisphere. 

The Antihelion radiant is now located at 21:20 (320) -14. This area of
the sky is located in on the Capricornus/Aquarius border 3 degrees north
of the 4th magnitude star Iota Capricorni. Any slow to medium speed
meteor from Capricornus or western Aquarius may be a good candidate for
this shower. Due to the many radiants currently active in this region
this source would be extremely difficult to distinguish and will most
likely be inadvertently combined with the Capricornid or Aquarid totals
even by experienced meteor observers. 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 1 per hour from
locations in the Northern Hemisphere and 2 meteors per hour from the
Southern Hemisphere. 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 Aquarid radiant is currently located at 21:44 (326) -08.
This area of the sky is located in western Aquarius 4 degrees southeast
of the 3rd magnitude star Sadalsuud (Beta Aquarii). Like the Alpha Caps
this radiant lies within the boundaries of the antihelion radiant area.
The NDA's are noticeably faster than the antihelion meteors at 42
km/sec. verses 30 km/sec. This 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. Like many of the radiants active this time of year
the NDA's are better seen from areas south of the northern tropics or 30
degrees north latitude. At this time expect to see only 1-2 shower
members per hour. 

The South Iota Aquarids become active this week. The radiant is located
at 21:48 (327) -16 which lies very close to the 3th magnitude star
Nashira (Delta Capricorni). This is still another radiant close to the
antihelion radiant. At 34 km/sec. They are just a bit faster than the
antihelion meteors. This radiant is also best placed between 0200 and
0300 LDT or 0100 to 0200 local standard time when it is located highest
in the southern sky. This showers peaks on August 4 this year so current
rates would be near 1 per hour.

The South Delta Aquarid radiant provides the strongest shower of July.
This radiant peaks in strength on Friday July 27. At this time rates
should be 15-20 shower members per hour as seen from the Southern
Hemisphere and the northern tropical regions. From the higher northern
latitudes rates should be only 5-10 per hour. Be sure to watch for these
meteors after moonset as moonlight will seriously reduce any activity.
The current radiant position lies at 22:36 (339) -16. This area of the
sky is located in southern Aquarius 4 degrees west of the 4th magnitude
star Delta Aquarii.  The radiant lies low in the southeast at dusk and
is not well seen until it approaches the meridian near 0300 local
daylight time or 0200 LST. These meteors encounter the earth at 41
km/sec., which is a bit faster than average. 

The Pisces Austrinid radiant is currently located at 22:48 (342) -29.
This position lies in eastern Pisces Austrinus only 2 degrees northwest
of the 1st magnitude star Fomalhaut (Alpha Piscis Austrini). These
meteors are of average velocity, slower than the Aquarids but faster
than the Alpha Caps and the antihelion meteors. Expect to see 0 to 1 an
hour from the Northern Hemisphere and 1-2 per hour south of the equator. 

The Northern Apex radiant is now located at 02:20 (035) +28. This
position lies in southern Triangulum 6 degrees northeast of the 2nd
magnitude star Hamal (Alpha Arietis). 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 Triangulum, northeastern Pisces,
northern Aries, or southern Perseus could be a good candidate. As seen
from the Northern Hemisphere this source should produce at least 2
meteors per hour during the last few hours before dawn. Rates seen from
the Southern Hemisphere would be less at 0-1 per hour. These meteors
appear very much like the Perseids and are often mistaken for early
Perseids by those not facing toward this portion of the sky. 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 02:20 (035) -02. This position lies in central Cetus only
1 degree from the famous variable star Mira (Omicron Ceti).
Unfortunately Mira is dim at this time and not a noteworthy beacon. 3rd
magnitude Delta Ceti is much easier to see located 4 degrees to the
northeast. 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 Cetus or southastern Pisces could be a candidate from this
source. Rates should be close to 2 per hour from most locations. 

The Perseids are now active in the morning sky producing 2-3 meteors per
hour as seen from the Northern Hemisphere. The radiant location is at
01:52 (028) +55, which places it in extreme northwestern Perseus. The
nearest bright star is 3rd magnitude Delta Cassiopeiae, which lies 7
degrees to the northwest. This area of the sky is highest just before
dawn so this would be the best time to try to see any Perseid activity.
These meteors are swift except when seen near the radiant or near the
horizon. They also produce many fine persistent trains. The Perseids
with become much more active as we approach their August 12 maximum.  

The Sporadic rates for the Northern Hemisphere have bottomed out and
will now finally beginning to increase. One would expect to see perhaps
5 random 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 1 random meteor can be seen per hour from the
Northern Hemisphere. Rates seen from the Southern Hemisphere are at
their highest level of the year with perhaps 8 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. Southern observers had better enjoy these strong rates now
since rates will soon plummet to far below those seen from the Northern
hemisphere.

Clear Skies 
Robert Lunsford 
AMS Visual Program Coordinator
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