Meteor Activity Outlook for August 10-16, 2007

August is the best month for viewing meteor
activity from the northern hemisphere. Not only is the activity enjoyable but
the balmy nights are much more pleasant than those experienced later in the year.
As the month begins the southern radiants are still active and often matching the
sporadic rates. The sporadic rates increase as the month progresses providing a
decent show for the normally slow evening hours. The Perseids kick
into high gear the second week of the month and fill the skies with colorful
streaks of light during the entire night. From the southern hemisphere activity
falls precipitously. This is much like what the northern hemisphere experiences
moving from January into February. The southern radiants put on a good show the
first week of the month. They taper off the second week and are nearly extinct by
the third. In the meantime the sporadic rates that were so impressive in early
July are now half as strong and still getting weaker. Unless you are located
near the equator you will not see much of the Perseids. From the southern
hemisphere any evening Perseids are impossible to see. You have to wait until
the last hours before dawn and hope that some will shoot upwards from low in the
northern sky.

During this period the moon reaches its new
phase on Sunday August 12. At this time the moon is located near the sun and is
invisible at night. Late in the period the waxing crescent moon will enter the
evening sky but will not interfere with meteor observing. The estimated total
hourly rates for evening observers this week is near four for those located north
of the equator and two for observers south of the equator. For morning observers
the estimated total hourly rates should be near fifty-five for those located in
the northern hemisphere and twenty for those viewing from 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 and rates listed below are exact
for Saturday night/Sunday morning August 11/12. 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. Doing this 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 18:52
(284) +58. This position is located in southern Draco, three 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 Alpha Capricornids (CAP) are active from a wide radiant located at 21:20
(320) -05. This position lies in western Aquarius, two degrees northwest of the
third magnitude star Sadalsuud (Beta Aquarii). The radiant is best placed near 0100 local
daylight time, when it lies highest in the sky. Current rates would be less than one per
hour, no matter your location. Don’t mix these meteors with the antihelion meteors,
which have a radiant just to the east. Both radiants need to be in your field of view
to properly sort these meteors. With an entry velocity of 23 km/sec., most activity
from this radiant would be slow.

The Antihelion (ANT) radiant is now centered at 22:08 (332) -09. This area
of the sky is located in a southwestern Aquarius, two degrees southwest of the
fourth magnitude star Theta Aquarii. 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 two per hour regardless of 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 located at 23:20
(350) -13. This position lies in eastern Aquarius, close to the fourth magnitude
star Omega Aquarii. The radiant is best placed near 0300 local
daylight time, when it lies highest in the sky. Current rates would be near two
per hour visible from the southern hemisphere and one per hour from the northern
hemisphere. With an entry velocity of 41 km/sec., most activity from this radiant
would be of average velocities.

The Perseids (PER) reach maximum activity on August 13 with average rates
expected to be near sixty shower members per hour. The current radiant position
lies at 03:04 (046) +58, which is located where the borders of Perseus, Cassiopeia,
and Camelopardalis meet. This position is also three degrees northwest of the
fourth magnitude star Eta Persei. While the radiant lies above the horizon for
most observers in the northern hemisphere, it is best placed 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.

Sporadic rates are now rising for observers in the northern hemisphere and
falling steadily for those located south of the equator. One would expect to see perhaps
twelve random meteors during the last hour before dawn from rural observing sites
in the northern hemisphere. 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.
As seen from the southern hemisphere late morning rates would now be near ten per
hour. During the first dark hour after the end of evening twilight, perhaps two
random meteors can be seen per hour, increasing to five by midnight.