(meteorobs) Meteor Activity Outlook for July 1-7, 2005

Robert Lunsford lunro.imo.usa at cox.net
Thu Jun 30 20:32:38 EDT 2005


This upcoming period will see the moon reaching its new phase on Wednesday
July 6. At this time the moon rises and sets with the sun and will not
interfere with observing. This weekend the waning crescent moon will rise an
hour or two before morning twilight. The moon's phase will be so thin that
it will not cause much interference to meteor observers. The estimated total
hourly rates for evening observers this week should be near two for those in
the Northern Hemisphere and three for those observers south of the equator.
For morning observers the estimated total hourly rates should be near seven
for those located in the Northern Hemisphere and ten for those in the
Southern Hemisphere. 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 2/3. 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. 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.

These are the showers that may be observed this week:

The Alpha Capricornids (CAP) are now producing a ZHR of one from a wide
radiant located at 18:52 (283) -17. This position lies in northern
Sagittarius, five degrees northwest of the third magnitude star Pi
Sagittarii. The radiant is best placed near 0100 local daylight time, when
it lies highest in the sky. 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. This radiant is located close
to the anthelion radiant this time of year and it may be difficult to
separate the two.

The Anthelion radiant is now centered at 19:40 (295) -21. This area of the
sky is located in eastern Sagittarius, eight degrees east of the third
magnitude star Pi Sagittarii. Since this radiant is large and diffuse, any
slow to medium speed meteor from eastern Sagittarius, southern Scutum or
western Capricornus could be a candidate for this shower. The center of this
area is best placed near 0200 local daylight time when it lies on the
meridian and is highest in the sky. At this time expect to see two shower
members per hour from the Southern Hemisphere and one from the Northern.

Unlike most of the annual showers the antihelion source is produced by
debris from unknown objects orbiting in a direct motion like the earth.
These objects are most likely asteroids, which produce stony and metallic
debris whose density is much greater than material produced by comets. There
is also the possibility that some of this activity may be caused by the
"Jupiter family of comets", comets which have been altered by Jupiter's
gravity into much shorter orbits. This material collides with the earth on
the inbound portion of its orbit, before its closest approach to the sun.
Therefore we best see them just after midnight when we are facing the
direction from which this activity appears. The antihelion source is active
all year from an area of the sky nearly opposite that of the sun. The center
of this source will move approximately one degree eastward per day and
travels through many different constellations over the course of a year. It
may make sense to list these meteors as anthelions or "ANT" but a majority
of meteor organizations prefer that you list them from the constellation in
which the radiant is currently located or the constellation where the shower
reaches maximum activity. Observers who send their reports to the
International Meteor Organization (I.M.O.) should label these meteors as
Sagittarids (SAG).

The Sporadic rates for the Northern Hemisphere are now rising from their low
plateau for the year. Observers can expect around six random meteors per
hour during the morning hours as seen from locations in the Northern
hemisphere. During the dark evening hours perhaps two random meteors can be
seen per hour north of the equator. Sporadic rates seen from the Southern
Hemisphere are near a secondary annual maximum. From south of the equator
one would expect to see approximately eight random meteors per hour during
the late morning hours and three per hour during the evening.

Alpha Capricornids (CAP)        18:52  (283)  -17
Hourly Rate =    <1  N.  Hemisphere,   <1  S. Hemisphere

Anthelion  (Sagittarids)    19:40 (295) -21
Hourly Rate =     1   N. Hemisphere,    2  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society
http://www.amsmeteors.org/lunsford/




More information about the Meteorobs mailing list