(meteorobs) Meteor Activity Outlook for June 28-July 4, 2008

Robert Lunsford lunro.imo.usa at cox.net
Fri Jun 27 13:12:05 EDT 2008


After several months of low activity the meteor rates for both hemispheres
see a marked increase in July. In the northern hemisphere the change is not
noticable until mid-month when several southern radiants, the Perseids, and
sporadic rates all increase in activity. Southern rates are good all month
long.

During this period the moon reaches its new phase on Thursday July 3rd. At
this time the moon will be located near the sun and will not be visible at
night. This weekend the waning crescent moon will produce minor interference
during the last few hours before dawn. As seen from the mid-northern
hemisphere (45 N) the estimated total hourly rates during the evening
observers would be near two. For morning observers the estimated total
hourly rates should be near ten. For those located in the mid-southern
hemisphere (45 S) morning rates would be near twenty and evening rates near
four. 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 and rates listed below are exact for Saturday
night/Sunday morning June 28/29. 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:

A few June Bootids (JBO) may be seen during the evening hours radiating from
a position near 15:00 (225) +47. This area of the sky lies in northern
Bootes, six degrees north of the fourth magnitude star Beta Bootis. This
radiant is best placed as soon as it becomes dark. Rates at this time should
be less than one for those located in the northern hemisphere and near zero
for observers south of the equator. With an entry velocity of 18 km/sec.,
the average June Bootid meteor would be of very slow speed.

The large Antihelion (ANT) radiant is now centered at 19:20 (290) -21. This
area of the sky lies in eastern Sagittarius, three degrees east of the third
magnitude star Pi Sagittarii. Actually any meteor from western Capricornus,
southern Aquila, as well as eastern Sagittarius could be a candidate for
this shower. This radiant is best placed near 0200 local daylight time (LDT)
when it lies on the meridian and is highest in the sky. Rates at this time
should be near three for northern observers and four for observers south of
the equator. With an entry velocity of 30 km/sec., the average Antihelion
meteor would be of medium-slow speed.

Studies by Sirko Molau of the IMO's video data has revealed an active
radiant located in southeastern Aquila. Maximum activity was reached on June
25, but activity continues through the 30th. The radiant lies at 20:16
(304) -07, which is located ten degrees southeast of the bright first
magnitude star Altair (Alpha Aquilae). This radiant is best placed near 0300
LDT when it lies on the meridian and is highest in the sky. Rates are most
likely less than one per hour regardless of your location. With an entry
velocity of 40 km/sec., the average North June Aquilid (NZC) meteor would be
of medium speed, but noticably more swift than the nearby Antihelion
radiant.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are
finally beginning to increase. One would expect to see approximately eight
random meteors during the last hour before dawn from rural observing sites
and two per hour during the evening hours. As seen from the mid-southern
hemisphere (45S) morning rates would be near seventeen per hour as seen from
rural observing sites and four per hour during the evening hours.

The table below presents a condensed version of the expected activity this
week. Rates and positions are exact for Saturday night/Sunday morning.

June Bootid (JBO)  15:00 (225) +47   Velocity - 18km/sec.
Northern Hemisphere - <1   Southern Hemisphere - 0

Antihelion (ANT) - 18:00 (270) -23   Velocity - 30km/sec.
Northern Hemisphere - 3   Southern Hemisphere - 4

North June Aquilid (NZC)  20:16 (304) -07   Velocity - 40km/sec.
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#X2008

Clear Skies!
Robert Lunsford
American Meteor Society










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