(meteorobs) Meteor Activity Outlook for August 22-28, 2009

[Robert Lunsford]

Meteor activity kicks into high gear in August as seen from the northern
hemisphere. The main reason for all this activity is the Perseid shower that
peaks on August 12. This shower is active most of the month and remains
above the level of the sporadic background for a week centered on August 12.
The sporadic activity is also increasing as seen from the northern
hemisphere and is now nearly double the rates from just three months ago. As
seen from south of the equator, meteor rates are still decent but falling
rapidly. The sporadic rates seen at the beginning of the month will be twice
as much as those seen during the last days of the month. The Perseid radiant
does not rise high into the sky as seen in the southern hemisphere so rates
from this shower are greatly reduced when compared to the northern
hemisphere.

During this period the moon reaches its first quarter phase on Thursday
August 27th. At that time the moon will set near 0100 local daylight time
LDT and will allow unhampered observing during the busy morning hours. This
weekend the waxing crescent moon will set shortly after the end of evening
twilight and will not be a factor at all. The estimated total hourly rates
for evening observers this week is near four as seen from the northern
hemisphere and three from the southern hemisphere. For morning observers the
estimated total hourly rates should be near twenty from the northern
hemisphere and twelve as seen from the southern hemisphere. 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 August 22/23. 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 Kappa Cygnids (KCG) are active from a wide radiant located at 19:08
(287) +60. This position is located in southern Draco, six degrees north of
the fourth magnitude star Kappa Cygni. Current rates would be near one
shower member per hour. With an entry velocity of 25 km/sec. most of these
meteors will appear to travel slower than average. The radiant is best
placed near 2300 Local Daylight Time (11pm LDT) when it lies nearly overhead
for much of the Northern Hemisphere. Due to its high northern declination
this activity is not well seen from the Southern Hemisphere.

The large Antihelion (ANT) radiant is now centered at 22:52 (343) -06. This
area of the sky lies in northeastern Aquarius, ten degrees north of the
third magnitude star Delta Aquarii. Actually any meteor from Aquarius,
eastern Capricornus, as well as western Pisces, could be a candidate for
this shower. 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 three
no matter your location. With an entry velocity of 30 km/sec., the average
Antihelion meteor would be of medium-slow speed.

The Delta Aquariids (SDA) are still active from a radiant at 23:56
(359) -10. This position lies on the Aquarius/Cetus border, fifteen degrees
northeast of the third magnitude star Delta Aquarii. The radiant is best
placed near 0300 LDT, when it lies highest in the sky. Current hourly rates
would be less than one from the northern hemisphere and one as seen from
south of the equator. With an entry velocity of 43 km/sec., most activity
from this radiant would be of average velocities.

The Perseids (PER) peaked on August 12th with good rates despite the
unfavorable lunar conditions. The current radiant position lies at 04:00
(060) +58, which is located in southern Camelopardalis, ten degrees north of
the second magnitude star Mirfak (Alpha Persei). The radiant is well placed
for those in the northern hemisphere during the last few hours before dawn.
Due to the high northern declination (celestial latitude) of the radiant,
rates witnessed from the southern hemisphere are very low when compared to
those seen north of the equator. Current hourly rates would be two from the
northern hemisphere and less than one as seen from south of the equator. At
59 km/sec., Perseid meteors are swift, often exhibiting persistent trains.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are
becoming more active. One would expect to see approximately thirteen random
meteors during the last hour before dawn from rural observing sites and
three per hour during the evening hours. As seen from the mid-southern
hemisphere (45S) morning rates would be near eight 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.

The list below presents a summary of the expected activity this week. Rates
and positions are exact for Saturday night/Sunday morning August 22/23, but
may be used all week.

Kappa Cygnids (KCG) 19:08 (287) +60  Velocity - 25km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - <1 per hr.

Antihelion (ANT) - 22:52 (343) -06  Velocity - 30km/sec.
Northern Hemisphere - 3 per hr. Southern Hemisphere - 3 per hr.

Delta Aquariids (SDA) 23:56 (359) -10  Velocity - 43km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - 1 per hr.

Perseid (PER) 04:00 (060) +58  Velocity - 59km/sec.
Northern Hemisphere - 2 per hr. Southern Hemisphere - <1 per hr.

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2009

Clear Skies!
Robert Lunsford
American Meteor Society