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(meteorobs) Meteor Activity Outlook for Feb 13-19, 2004

The moon reaches its last quarter phase on Friday February 13. At this time
the moon lies ninety degrees west of the sun and rises near midnight local
standard time. One can observe successfully if the moon is kept out of your
field of view.  It would probably be most productive to face toward the
northern half of the sky if the moon is above the horizon. As the week
progresses, the moon will become less of a factor as becomes a thin crescent
and rises later in the morning. The estimated total hourly rates for evening
observers this week should be near two for those in the Northern Hemisphere
and three for those south of the equator. For morning observers the
estimated total hourly rates should be near seven for those located in the
Northern Hemisphere and sixteen 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.  Morning rates are reduced due
to moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning February 14/15. The radiants do not change greatly day to day so the
given positions may be used during this entire period. Most star atlases
(available at science stores and libraries) 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 location. 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 last rise later in the night. This list also
provides the order of ascending velocity for each radiant with those listed
first usually being much slower than those last on the list. Velocity should
not be the prime factor for shower association as all showers can produce
slow meteors. Slow meteors can be produced from normally swift showers, such
as the Leonids, when meteors appear near the radiant or close to the
horizon. The true velocity is only revealed in shower members seen far from
the radiant and high in the sky.

The Delta Velids (DVE) is a shower listed among radiants of the Dutch Meteor
Society. The date of maximum activity is February 15 with a predicted ZHR of
one.  With such low activity care must again be taken to exclude any
sporadic activity from the Delta Velid count. The radiant currently lies at
08:44 (131) -52. This position lies in western Vela, three degrees north of
the second magnitude star Delta Velorum. This radiant is only seen well from
the northern equatorial regions southward. The area of the sky is also best
placed near midnight local standard time. At 35 km/sec. the Delta Velids
produce meteors of average velocity.

The Delta Leonids (DLE) peak on February 25 with a ZHR of two. Current rates
would be less than one per hour. The radiant is located at 10:40 (160) +19.
This area of the sky is located in central Leo, four degrees east of the
second magnitude star Algeiba (Gamma Leonis). This position is close to the
antihelion source so care must be taken to separate the two. It is quite
possible that this radiant is a northern branch of the antihelion source,
active this time of year. The best time to view this activity is near 0100
local time, when the radiant lies on the meridian and at its highest point
in the sky. With an entry velocity of 23 kilometers per second, these
meteors will appear to move slowly.

The Antihelion radiant is now centered at 10:40 (160) +08. This area of the
sky is located in southern Leo, two degrees southeast of the fourth
magnitude star Rho Leonis. Since this radiant is large and diffuse, any slow
to medium speed meteor from southern Leo or northern Sextans could be a
candidate for this shower. The center of this area is best placed near 0100
local standard time when it lies on the meridian and is highest in the sky.
At this time expect to see one shower member per hour regardless of your
location.

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. 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 antihelions 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. Those who send their data to the International Meteor Organization
should call these meteors Virginids (VIR).

The Omicron Centaurids (OCE) are one of several radiants that are active in
Centaurus during late January and throughout the month of February. The date
of maximum activity is February 15 with a predicted ZHR of two.  The radiant
lies at 11:48 (177) -56. This position is in southwestern Centaurus, eight
degrees west of the second magnitude star Gacrux (Gamma Crucis). Due to the
southern declination this shower is not well seen north of the northern
tropical regions. This area of the sky is best placed near 0300 local
standard time when it lies highest in the sky. At 51 km/sec. the Omicron
Centaurids produce meteors of medium-swift velocity.

The Theta Centaurids (TCE) is the first of several radiants that are active
in Centaurus during late January and throughout the month of February. The
date of maximum activity is February 15 with a predicted ZHR of four. The
radiant lies at 14:00 (210) -41. This position is in central Centaurus, five
degrees south of the second magnitude star Theta Centauri. This shower is
not well seen north of the northern tropical regions. It is possible to see
activity from the latitude of San Diego, CA as I have witnessed several of
these meteors during my winter observations. This area of the sky is best
placed near 0500 local standard time when it lies highest in the sky. At 60
km/sec. the Theta Centaurids produce meteors of swift velocity.

The Alpha Centaurids (ACE) are the strongest of the radiants that are active
in Centaurus during late January and throughout the month of February. The
date of maximum activity is February 9 with a predicted ZHR of seven.
Current ZHR's would be near three. The radiant lies at 14:36 (219) -61. This
position is in southeastern Centaurus very close to the brilliant zero
magnitude star Rigel Kentaurus (Alpha Centauri). Due to the southern
declination this shower is not well seen north of the northern equatorial
regions. This area of the sky is also best placed near 0500 local standard
time when it lies highest in the sky. At 56 km/sec. the Alpha Centaurids
produce meteors of swift velocity.

The Northern Apex radiant is now centered at 15:40 (235) -04. This position
lies on the Libra/Serpens Caput border, two degrees west of the fourth
magnitude star Mu Serpentis. This area of the sky is best placed for viewing
during the last dark hour before dawn when it lies highest in the sky. Since
this radiant is large and diffuse, any meteor from western Ophiuchus,
southern Serpens Caput or northern Libra could be a candidate from this
source. Rates would be now close to one per hour regardless of your
location.

Like the antihelion area, both apex areas are active all year long and
travel approximately one degree eastward per day. Unlike the antihelion
debris, these particles orbit the sun in a retrograde motion opposite that
of the earth and are most likely produced by unknown comets. They strike the
earth after their closest approach to the sun. Since they are moving in
opposite directions these particles strike the earth at tremendous
velocities often creating bright meteors with persistent trains. These
particles strike the earth on the morning side of earth and are best seen
just before morning twilight while the sky is still perfectly dark. This is
not really a "shower" per se, but an artificial radiant created by the
Earth's motion through space. Meteors from both branches are normally
included in the sporadic count. I feel it is a worthy project to see if it
is possible to distinguish these meteors from the normal sporadic
background. On rare occasions there are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90 degrees
west of the sun. In simplistic terms, these meteors are seldom seen since
the Earth "sweeps clean" much of the material that shares the same orbit as
our planet. Much more material is located just north and south of the
earth's orbit with slightly higher or lower inclinations. This creates the
northern and southern branches of the apex activity.

The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 15:40 (235) -34. This position lies in northern Lupus, four
degrees south of the fourth magnitude star Tau Librae. Like the northern
apex, these meteors are best seen toward dawn when the radiant lies highest
above the horizon in a dark sky. Since this radiant is also large and
diffuse, any meteor from eastern Centaurus, southeastern Libra, western
Scorpius or northern Lupus could be a candidate from this source. Rates
would now be less than one per hour in the Northern Hemisphere and two per
hour in the Southern Hemisphere.

The Sporadic rates for the Northern Hemisphere are now past their annual
peak. One would currently expect to see perhaps five random meteors per hour
during the last hours before dawn from rural observing sites. This estimate
and the morning estimate for the Southern Hemisphere does not include the
apex meteors listed above. During the evening hours perhaps two random
meteors can be seen per hour from the Northern Hemisphere. Rates seen from
the Southern Hemisphere are now slightly stronger than those seen in the
northern skies with perhaps six random meteors being seen per hour during
the early morning hours and three per hour during the evening.  Morning
rates are reduced due to moonlight.

Clear Skies!
Robert Lunsford
AMS Operations Manager

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