(meteorobs) Meteor Activity Outlook for July 6-12, 2007

[Robert Lunsford]

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.

Alpha Capricornid (CAP) 19:12 (288) -15
Northern Hemisphere - 1   Southern Hemisphere - 1

Antihelion (ANT) - 19:52 (298) -19
Northern Hemisphere - 1   Southern Hemisphere - 2

Beta Aquarids (BAQ)  21:00 (315) -04
Northern Hemisphere - <1   Southern Hemisphere - <1

Delta Aquarids (SDA)  21:32 (323) -20
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#X2007

Clear Skies!
Robert Lunsford
American Meteor Society