(meteorobs) Meteor Activity Outlook for July 22-28, 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 new phase on Tuesday July 25th. This
weekend the waning crescent moon will rise near the start of morning
twilight and will not be a factor in observing. As the week progresses the
waxing crescent moon will enter the evening sky but will set soon after it
becomes dark. Once again it will not cause any interference to observers.
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 ten for those in the northern hemisphere and twenty 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.

The radiant positions listed below are exact for Saturday night/Sunday
morning July 22/23. 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 located at 20:04
(301) -11. This position lies in southeastern Aquila, four degrees northwest
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 Antihelion (ANT) radiant is now centered at 20:52 (313) -16. This area
of the sky is located in central Capricornus, three degrees west of the
third magnitude star Theta 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) are active from a radiant located at 22:20
(335) -18. This position lies in southwestern Aquarius, four degrees
southeast of the fourth magnitude star Iota Aquarii. The radiant is best
placed near 0300 local daylight time, when it lies highest in the sky.
Currently this should be the most active radiant with rates of 5-15 per
hour, depending on your latitude. 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. This
shower peaks on July 28 with expected ZHR's near twenty.

The Pisces Austrinids (PAU) are currently active from a radiant located at
22:24 (336) -32. This area of the sky lies in central Pisces Austrinus, two
degrees west of the fourth magnitude star Beta Piscis Austrini. This shower
peaks on the July 28 with ZHR's of five. Current rates would be three per
hour as seen from the most favored southern latitudes, where the radiant
rises higher in the sky. From the Northern Hemisphere rates would only be
1-2 per hour. 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 has now surpassed one shower member per hour. This
rate will slowly increase throughout the remainder of July and will peak on
the morning of August 12. The current radiant position lies at 01:12 (018)
+53, which is located in southern Cassiopeia, two degrees south of the
fourth magnitude star Theta Cassiopeiae. 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 or non-existent. 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 ten random meteors during the last hour before dawn from rural
observing sites. During the first dark hour after the end of evening
twilight, perhaps three 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.

Alpha Capricornids (CAP) 20:04 (301) -11 23
Northern Hemisphere 2 - Southern Hemisphere 2

Antihelion (ANT) - 20:52 (313) -16
Northern Hemisphere 2 - Southern Hemisphere 3

Southern Delta Aquarids (SDA) 20:52 (313) -16
Northern Hemisphere 5 - Southern Hemisphere 7

Pisces Austrinids (PAU) 22:24 (336) -32
Northern Hemisphere 1 - Southern Hemisphere 2

Perseids (PER) 01:12 (018) +53
Northern Hemisphere 1 - Southern Hemisphere >1

*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