Meteor Activity Outlook for July 13-19, 2007

For observers in the northern hemisphere meteor
activity finally picks up in July after months of low rates. Several showers
become active this month and peak toward the end of the month. Sporadic activity
increases with each passing week throughout the northern summer. Activity seen in
the southern hemisphere is peaking and will remain strong throughout the month.
Later in the month strong minor shower activity will offset the falling sporadic
rates in the south. Sporadic rates as seen from the southern hemisphere are
highest early in the month and then fall quite steeply as the southern winter
progresses.

During this period the moon reaches its new
phase on Saturday July 14. At this time the moon is located near the sun as seen
in the sky and not visible at night. Later in the period the thin waxing crescent
moon will enter the evening sky but will set well before the prime morning observing
hours. The estimated total hourly rates for evening observers this week is near three
for those located north of the equator and four for observers south of the equator.
For morning observers the estimated total hourly rates should be near fifteen 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 listed below are exact for Saturday
night/Sunday morning July 14/15. 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 Alpha Capricornids (CAP) are active from a wide radiant located at 19:36
(294) -14. This position lies in northeastern Sagittarius, seven degrees southwest
of the third magnitude star Alpha Capricornii. The radiant is best placed near
0100 local daylight time, when it lies highest in the sky. Current rates would be
near one per hour, no matter your location. Don’t mix these meteors with the more
numerous 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. 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 20:20 (305) -18. This area
of the sky is located in a western Capricornus, four degrees south of the third
magnitude star Dabih (Beta Capricornii). 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 as seen in the northern hemisphere and three per hour for those
located south of the equator. With an entry velocity of 30 km/sec., the average
antihelion meteor would be of medium-slow speed.

Sirko Molau’s study of video radiants has revealed activity during the
period July 8-15, from an area in northwestern Aquarius. Maximum occured on July
10 with the radiant located at 21:00 (315) -04. This position lies five degrees
northwest of the third magnitude star Sadalsuud (Beta Aquarii). This radiant is
best placed near 0300 LDT when it lies highest in the sky. It appears that nine
percent of the total sporadic activity for the night is related to this radiant.
This would equate to only 1-2 shower members per hour at best. At
40km/sec., the average meteor from this radiant would be of medium velocity.

Sirko Molau’s study of video radiants has revealed another center of activity located
at 21:32 (323) -02. This radiant is active during the period July 18-23, from an
area in northern Aquarius. This position lies four degrees southwest of the third
magnitude star Sadalmelik (Alpha Aquarii). Maximum occurs on July 20. This
radiant is best placed near 0300 LDT when it lies highest in the sky. It appears
that seven percent of the total sporadic activity for the night is related to this
radiant. This would only provide 1-2 shower members per hour at best. At 39km/sec.,
the average meteor from this radiant would be of medium velocity.

The Delta Aquariids (SDA) are active from a radiant located at 21:56
(329) -19. This position lies in eastern Capricornus, four degrees southeast of
the variable star Epsilon Capricornii. The radiant is best placed near 0400 local
daylight time, when it lies highest in the sky. Current rates would be low perhaps
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. 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.

Sirko Molau’s study of video radiants has revealed early Perseid activity peaking
on July 20. The radiant is then located at 00:48 (012) +51, which places it
southern Cassiopeia, six degrees south of the second magnitude star Shedar
(Alpha Cassiopeiae). This radiant is best placed at dawn when it lies highest in
the sky. This enhancement of Perseid meteors is active July 15-22 when rates may
rise to 2-3 per hour. At 52km/sec., the average meteor from this radiant would be
of medium-swift velocity with a good percentage of trains.

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

^The main Perseid display peaks on August 13.