Meteor Activity Outlook for August 15-21, 2009

Meteor activity kicks into high gear in August
as seen from the northern hemisphere. The main reason for all this activity is
the Perseid shower that peaks on August 12. This shower is active most of the month
and remains above the level of the sporadic background for a week centered on
August 12. The sporadic activity is also increasing as seen from the northern
hemisphere and is now nearly double the rates from just three months ago. As seen
from south of the equator, meteor rates are still decent but falling rapidly. The
sporadic rates seen at the beginning of the month will be twice as much as
those seen during the last days of the month. The Perseid radiant does not
rise high into the sky as seen in the southern hemisphere so rates from this
shower are greatly reduced when compared to the northern hemisphere.

During this period the moon reaches its new
phase on Thursday August 20th. At that time it will rise and set with the sun and
will not be visible at night. This weekend the waning crescent moon will not pose
much of a problem as long as meteor observers keep it out of their field of view.
The estimated total hourly rates for evening observers this week is near six as
seen from the northern hemisphere and three from the southern hemisphere. For
morning observers the estimated total hourly rates should be near twenty two from
the northern hemisphere and sixteen 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.

The radiant positions and rates listed below are exact
for Saturday night/Sunday morning August 15/16. 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 Kappa Cygnids (KCG) are active from a wide radiant located at 19:00
(285) +59. This position is located in southern Draco, five degrees northwest of
the fourth magnitude star Kappa Cygni. Current rates would be near one shower
member per hour. With an entry velocity of 25 km/sec. most of these meteors will
appear to travel slower than average. The radiant is best placed near 2300 Local
Daylight Time (11pm LDT) 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 large Antihelion (ANT) radiant is now centered at 22:24 (336) -08.
This area of the sky lies in central Aquarius, just east of the fourth magnitude
star Theta Aquarii. Actually any meteor from Aquarius, eastern Capricornus, as
well as western Pisces, 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 three no matter your location. With an
entry velocity of 30 km/sec., the average Antihelion meteor would be of
medium-slow speed.

The Delta Aquariids (SDA) are active from a radiant at 23:28 (352) -12.
This position lies in eastern Aquarius, four degrees southeast of the fourth
magnitude star Psi 2 Aquarii. The radiant is best placed near 0300 LDT, when it
lies highest in the sky. Current hourly rates would be one from the northern
hemisphere and two as seen from south of the equator. With an entry velocity of
43 km/sec., most activity from this radiant would be of average velocities.

The Perseids (PER) peaked on August 12th with good rates despite the
unfavorable lunar conditions. The current radiant position lies at 03:28 (052)
+58, which is located in southern Camelopardalis, eight degrees north of the
second magnitude star Mirfak (Alpha Persei). 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 witnessed from the
southern hemisphere are very low when compared to those seen north of the equator.
Current hourly rates would be five from the northern hemisphere and two as seen
from south of the equator. At 59 km/sec., Perseid 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 three per hour
during the evening hours. As seen from the mid-southern hemisphere (45S) morning
rates would be near nine per hour as seen from rural observing sites and two
per hour during the evening hours. Locations between these two extremes would see
activity between the listed figures.

The table below presents a summary of the expected activity this week. Rates and
positions are exact for Saturday night/Sunday morning August 15/16, but may be used
all week.