(meteorobs) Meteor Activity Outlook for August 14-20, 2010

[Robert Lunsford]

Meteor activity kicks into high gear in August as seen from the northern hemisphere. The main reason for this activity surge is the 
Perseid shower that peaks on August 13. This shower is active most of the month and remains above the level of the sporadic 
background for a week centered on August 13. 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 high 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 Monday August 16th. At this time the moon will be located ninety 
degrees east of the sun and will set near 0100 local daylight time (LDT) for locations in the mid-northern latitudes of the northern 
hemisphere. This weekend the waxing crescent moon will set a bit just prior to midnight for the locations mentioned above, and will 
be gone from the sky during the active morning hours. The estimated total hourly rates for evening observers this week is near three 
no matter your location. For morning observers the estimated total hourly rates should be near thirty-five from the northern 
hemisphere and twenty 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. Evening rates are slightly 
reduced this week due to moonlight.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday 
night/Sunday morning August 14/15. 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:

Activity from the August Draconids (AUD) are currently active from a radiant located at 18:14 (273) +62. This position lies in 
southern Draco, ten degrees north of the second magnitude star Eltanin (Gamma Draconis). Maximum activity is not predicted until 
August 21st so current rates would be low, less than one per hour. With an entry velocity of 23 km/sec. most of these meteors will 
appear to move slowly. The radiant is best placed near 2200 Local Daylight Time (10pm LDT) when it lies highest in the sky. Due to 
its high northern declination this shower is not well seen from the southern hemisphere.

The Kappa Cygnids (KCG) are active from a wide radiant located at 19:06 (287) +52. This position is further south than previous 
publications. It has been updated through the use of video observations by the International Meteor Organization. The new location 
lies on the Cygnus/Draco border, three degrees southwest of the faint star Kappa Cygni. Maximum activity occurred on August 14th so 
current rates would be near two per hour from the northern hemisphere and less than one shower member per hour from south of the 
equator. With an entry velocity of 23 km/sec. most of these meteors will appear to travel slower than average. The radiant is best 
placed near 2300 LDT (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 wide Antihelion (ANT) radiant is now centered at 22:20 (335) -08. This area of the sky lies in central Aquarius, three degrees 
southeast of the fourth magnitude star Theta Aquarii. This radiant is best placed near 0200 LDT when it lies on the meridian and is 
located highest in the sky. Due to the large size of this radiant, any meteor radiating from northern Piscis Austrinus, Capricornus, 
Aquarius, or southern Pegasus could be a candidate for this shower. Rates at this time should be near two per hour 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) reached maximum activity on July 30th. The shower is still active from a radiant located at 23:36 
(354) -12. This position lies in eastern Aquarius, three degrees northwest of the fourth magnitude star Omega 2 Aquarii. The radiant 
is best placed near 0300 LDT, when it lies highest in the sky. With an entry velocity of 42 km/sec., most activity from this radiant 
would be of average velocities. Expect rates of less than one per hour north of the equator and one per hour from the southern 
hemisphere.

Another new shower discovered by Sirko Molau and Juergen Rendtel from the IMO's video database are the Eridanids (ERI). This shower 
is active from August 4th through the 18th with maximum activity occurring on the 9th. Hourly rates could reach near two per hour at 
maximum. This shower was observed by me during the Perseid maximum last week. The radiant is currently located at 03:12 (048) -09. 
This area of the sky is located in western Eridanus, three degrees east of the faint star Eta Eridani. This radiant is best placed 
during the last hour before dawn when it lies highest in a dark sky. Hourly rates are expected to be less than one. With an entry 
velocity of 64 km/sec., the average Eridanid meteor would be swift.

The Perseids (PER) reached maximum activity on Friday August 13th with zenith hourly rates (ZHR's) near 90. They are still active 
from a radiant located at 03:24 (051) +58. This position actually lies in southern Camelopardalis, eight degrees north of the second 
magnitude star Mirfak (Alpha Persei). The radiant is best placed during the last hour before the start of morning twilight when it 
lies highest in a dark sky. Current rates would be near twenty per hour, falling to less than ten by the end of the week. Activity 
from the Perseids is not well seen south south of the equator and completely invisible south of 40 degrees south latitude. With an 
entry velocity of 61 km/sec., most activity from this radiant would be swift.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately thirteen sporadic meteors per hour during the 
last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern 
hemisphere (45S), morning rates would be near nine 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. Rates are slightly reduced during the 
evening hours due to moonlight.

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

August Draconids (AUG) - 18:14 (273) +62    Velocity - 23km/sec.
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr.

Kappa Cygnids (KCG) - 19:06 (287) +52   Velocity - 23km/sec.
Northern Hemisphere - 1 per hr.   Southern Hemisphere - <1 per hr.

Antihelion (ANT) - 22:20 (335) -08   Velocity - 30km/sec.
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 3 per hr.

Delta Aquariids (SDA) - 23:12 (348) -14    Velocity - 42km/sec.
Northern Hemisphere - 1 per hr.   Southern Hemisphere - 2 per hr.

Eridanids (ERI) - 03:12 (048) -09    Velocity - 64km/sec.
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 2 per hr.

Perseids (PER) - 03:24 (051) +58   Velocity - 61km/sec.
Northern Hemisphere - 3 per hr.   Southern Hemisphere - 2 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#X2010

Clear Skies!
Robert Lunsford
American Meteor Society