Meteor Activity Outlook for July 6-12, 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, then fall quite steeply as the southern winter progresses.

During this period the moon reaches its last quarter
phase on Saturday July 7. At this time the moon rises near 0100 local daylight
time (LDT) and will remain in the sky the remainder of the morning. The moon becomes
less of a factor with each passing night as it wanes toward its new phase. The
estimated total hourly rates for evening observers this week is near two 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 nine for those
located in the northern hemisphere and sixteen 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. Morning rates are reduced due to moonlight.

The radiant positions listed below are exact for Saturday
night/Sunday morning July 7/8. 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 Alpha Capricornids (CAP) are active from a wide radiant located at 19:12
(288) -15. This position lies in eastern Sagittarius, four degrees east of the
second magnitude star Nunki (Sigma Sagittarii). 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 19:52 (298) -19. This area
of the sky is located in a remote area of eastern Sagittarius, seven degrees southwest
of the third third magnitude star Dabih (Beta Capricorni). 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 one per hour as seen in the northern hemisphere
and two 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 occurs 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. With a bright
moon in the sky, seeing any activity from this radiant would be difficult. At
40km/sec., the average meteor from this radiant would be of medium velocity.

The Delta Aquarids (SDA) are active from a radiant located at 21:32
(323) -20. This position lies in eastern Capricornus, close to the variable
star Epsilon Capricornii. The radiant is best placed near 0300 local daylight time,
when it lies highest in the sky. Current rates would be very low, especially with
the moon still in the morning sky. 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.

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
six 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 two random meteors can be seen per hour. Sporadic rates
increase as the night progresses so rates seen near midnight would be near four
per hour. Late morning sporadic rates seen from the southern hemisphere are now
near twelve 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. Morning rates are reduced due to moonlight.