Meteor Activity Outlook for May 30-June 5, 2009

June is another slow month for meteor activity.
There are no major showers active in June and only the Antihelion source can be
counted on for continuous activity. Even the Antihelion is located so far south
this time of year that rates rarely exceed two per hour as seen from the northern
hemisphere. Sporadic rates reach their nadir in June as seen from the mid-northern
hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45
S) continue to rise this month toward a maximum in July.

During this period the moon reaches its first
quarter phase on Sunday May 31. At this time the moon lies ninety degrees east of
the sun and is above the horizon during the evening hours. It sets near 0100 local
daylight time (LDT) and the remainder of the night is free of interfering moonlight.
Later in the period the waxing gibbous moon will set later and later, reducing the
window of opportunity for viewing under truly dark conditions. The estimated total
hourly rates for evening observers this week is near two as seen from the northern
hemisphere and three for those situated south of the equator. For morning observers
the estimated total hourly rates should be near seven for those located in the
mid-northern hemisphere (45 N) and seventeen for those viewing from the mid-southern
hemisphere (45 S). Locations between these two extremes would see activity between
the listed figures. 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. Evening rates are reduced due to
moonlight.

The radiant positions and rates listed below are exact
for Saturday night/Sunday morning May 30/31. 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. Viewing there 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 wide Antihelion (ANT) radiant is now centered at 17:32 (263) -23. This
area of the sky lies in extreme southeastern Ophiuchus, three degrees northeast
of the third magnitude star Theta Ophiuchi. This radiant is best placed near 0200
LDT when it is located on the meridian and lies highest in the sky above
the horizon. Due to the large size of this radiant, any meteor radiating from
southern Ophiuchus,northern Scorpius, western Sagittarius, or southern Serpens
Cauda could be a candidate for this shower. Rates at this time should be near
two per hour as seen from the southern hemisphere and one as seen from north
of the equator. With an entry velocity of 30km/sec., the average Antihelion meteor
would be of medium-slow speed.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately
six Sporadic meteors per hour during the last hour before dawn as seen
from rural observing sites. Evening rates would be near one per hour. As seen from
the mid-southern hemisphere (45S), morning rates would be near fifteen per hour as
seen from rural observing sites and two per hour during the evening hours. Locations
between these two extremes would see activity between the listed figures. Evening
rates are reduced due to moonlight.

The table below presents a summary of the expected activity this week. Rates and
positions are exact for Saturday night/Sunday morning but may be used all week.