(meteorobs) Meteor Activity Outlook for July 28-August 3, 2006

[Robert Lunsford]

During July observers in the northern hemisphere witness a surge in meteor
activity, especially during the second half of the month. The source of this
increase is increased sporadic rates along with several showers located
opposite the sun. The Perseids also become active in mid-July with
increasing rates as the Earth nears the August 12 maximum. During the first
week of the month, observers south of the equator are enjoying some of their
best rates of the year. This activity is produced by the strongest sporadic
rates of the year and the fact that the Antihelion radiant is positioned
well south of the celestial equator this time of year. During the second
half of the month the sporadic rates begin to plummet and are the equal of
rates seen in the northern hemisphere by the end of the month.

This week the moon will reach its first quarter phase on Wednesday August
2nd. This weekend the waxing crescent moon will set during the evening hours
and will not interfere with morning observing, the time when activity is at
its best. As the week progresses the moon will set later and later but will
still leave a large window of dark sky between the time of moonset and the
start of morning twilight. The estimated total hourly rates for evening
observers this week is near two for observers in the northern hemisphere and
three for those south of the equator. For morning observers the estimated
total hourly rates should be near thirty two for those in the northern
hemisphere and thirty six for those 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. Evening rates are reduced due to
moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning July 30/31. 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. 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 Alpha Capricornids (CAP) are active from a wide radiant centered at
20:32 (308) -10. This position lies in northwestern Capricornus, three
degrees northeast of the wide third magnitude double star Alpha Capricorni.
The radiant is best placed near 0100 local daylight time, when it lies
highest in the sky. Current rates would be near two per hour, no matter your
location. With an entry velocity of 23 km/sec., most activity from this
radiant would be slow. This radiant is well seen except for far northern
latitudes where it remains twilight all night long and the radiant does not
rise as high into their sky. The Alpha Caps are also known for producing
impressive fireballs.

The Antihelion (ANT) radiant is now centered at 21:16 (319) -14. This area
of the sky is located in central Capricornus, three degrees northwest of the
fourth magnitude star Iota Capricornii. This radiant is best placed near
0200 local daylight time when it lies on the meridian and is highest in the
sky. Rates at this time should be near two per hour for those north of the
equator and three per hour south of the equator. With an entry velocity of
30 km/sec., the average Antihelion meteor would be of medium-slow speed.
Please note that commencing in 2007; the International Meteor Organization
will suggest that visual observers include the North Delta Aquarids and both
branches of the Iota Aquarids as Antihelions. If observers wish to begin in
2006, the AMS has no objections.

The Southern Delta Aquarids (SDA) reached maximum activity on July 28, with
rates between 10 and 20, depending on your latitude. The radiant is located
at 22:40 (340) -16. This position lies in southern Aquarius, three degrees
west of the third magnitude star Delta Aquarii. The radiant is best placed
near 0300 local daylight time, when it lies highest in the sky. Observers
near 20 degrees south latitude are most favored with longer nights and the
radiant passing through the zenith. With an entry velocity of 41 km/sec.,
most activity from this radiant would be of average velocities. These
meteors tend to be faint so the darkest skies are necessary in order to see
this shower well.

The Pisces Austrinids (PAU) also peak on July 28, but are much weaker than
the Southern Delta Aquarids. Visual rates rarely exceed three per hour, even
where the radiant passes through the zenith. The radiant is located at 22:52
(343) -29. This area of the sky lies just one degree west of the bright star
Fomalhaut (Alpha Piscis Austrini). These meteors are best seen near 0300
LDT, when the radiant lies highest above the horizon. These meteors are of
average velocity, slower than the Aquarids but faster than the Alpha Caps
and the antihelion meteors.

Perseid (PER) activity is now near five per hour, as seen from the northern
hemisphere. This rate will slowly increase as we approach the peak on the
morning of August 12. The current radiant position lies at 01:56 (029) +54,
which is located in extreme northwestern Perseus, five degrees southwest of
the famous "Double Cluster" in Perseus. The radiant is well placed for those
in the Northern Hemisphere during the last few hours before dawn. Due to the
high northern declination (celestial latitude) of the radiant, rates seen
from the Southern Hemisphere are very low when compared to those seen north
of the equator. At 59 km/sec., Perseid meteors are swift, often exhibiting
persistent trains.

After six months of declining rates the Sporadic rates for the Northern
Hemisphere are now finally starting to increase. One would expect to see
perhaps eleven random meteors during the last hour before dawn from rural
observing sites. During the first dark hour after the end of evening
twilight, perhaps two random meteors can be seen per hour. Sporadic rates
increase as the night progresses so rates seen near midnight would be near
six per hour. Sporadic rates seen from the southern hemisphere have now
reached a secondary maximum and are now starting to fall. One would see
approximately twelve random meteors per hour during the last hour before
dawn and three per hour during the first dark hour after the end of evening
twilight. Rates near midnight would be near eight per hour. Evening rates
are reduced due to moonlight.

Alpha Capricornids (CAP)   20:32 (308) -10
Northern Hemisphere 2 - Southern Hemisphere 2

Antihelion (ANT)   21:16 (319) -14
Northern Hemisphere 2 - Southern Hemisphere 3     02:00

Southern Delta Aquarids (SDA)   22:40 (340) -16
Northern Hemisphere 10 - Southern Hemisphere 15

Pisces Austrinids (PAU)   22:52 (343) -29
Northern Hemisphere 2 - Southern Hemisphere 3

Perseids (PER)   01:56 (029) +54
Northern Hemisphere 5 - Southern Hemisphere 2

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2006

Clear Skies!
Robert Lunsford
American Meteor Society