(meteorobs) Meteor Activity Outlook for July 31-August 6, 2010

[Robert Lunsford]

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 noticeable 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 last quarter phase on Tuesday August 3rd. At this time the moon will be located ninety 
degrees west of the sun and will rise near 0100 local daylight time (LDT) for those located in the mid-northern latitudes. This 
weekend the waning gibbous moon will be in the sky most of the night making it difficult to view any meteor activity. As the moon 
passes its last quarter phase the situation improves as long as one observes with the the moon far from their field of view. The 
estimated total hourly rates for evening observers this week is near four no matter your location. For morning observers the 
estimated total hourly rates should be near seventeen from the northern hemisphere and twenty-one 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. During this period, moonlight reduces activity seen during the morning hours.

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 July 31/ August 1. 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 Alpha Capricornids (CAP) are active from a wide radiant located at 20:30 (307) -09. This position lies in northwestern 
Capricornus, two degrees northeast of the third magnitude double star Alpha Capricornii. The radiant is best placed near 0100 local 
daylight time (LDT), when it lies on the meridian and is highest in the sky. Current rates should be near two per hour as seen from 
the northern hemisphere and three per hour from the southern. Don't confuse these meteors with the antihelion meteors, which have a 
radiant just to the east. Both radiants need to be in your field of view to properly sort these meteors. With an entry velocity of 
25 km/sec., most activity from this radiant would be slow, a bit slower than the antihelions. This radiant is well seen except for 
far northern latitudes where it remains twilight all night long and the radiant does not rise as high into their sky.

The wide Antihelion (ANT) radiant is now centered at 21:24 (321) -13. This area of the sky lies in northern Capricornus. The nearest 
bright star is fourth magnitude Iota Capricornii, which lies three degrees to the southwest. This radiant is best placed near 0200 
local daylight time (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 northwestern Piscis Austrinus, Microscopium, Capricornus, western Aquarius, or southeastern Aquila could be a 
candidate for this shower. Rates at this time should be near two per hour as seen from the northern hemisphere and three per hour as 
seen from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.

The Delta Aquariids (SDA) reach maximum activity on Friday July 30th. Unfortunately the bright moon will obscure most of the 
activity from this shower. The radiant is located at 22:48 (342) -16. This position lies in southwestern Aquarius, just west of the 
third magnitude star Delta Aquarii. The radiant is best placed near 0300 LDT, when it lies highest in the sky. The optimal latitudes 
for viewing this shower lie in the southern tropics where the radiant passes overhead. With an entry velocity of 42 km/sec., most 
activity from this radiant would be of average velocities.

A new shower discovered by Sirko Molau and Juergen Rendtel from the IMO's video database are the August Piscids (AUP). This shower 
is only active on eight nights from August 2-9 with maximum activity occurring on the 4th. At maximum, the radiant is located at 
00:30 (008) +18. This area of the sky is located in western Pisces, four degrees northwest of the third magnitude star Algenib 
(Gamma Pegasi). This position is also suspiciously close (15 degrees east) to the radiant of the 1970's radiant known as the Upsilon 
Pegasids. Little has been reported of this radiant recently. 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 66 km/sec., the average August 
Piscid meteor would be swift.

The Perseids (PER) are active from a radiant located at 02:03 (031) +55. This position lies in western Perseus, twelve degrees north 
of the famous second magnitude double star Almach (Gamma Andromedae). 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 two to three per hour at best, as seen from the 
northern hemisphere. Activity from this source is not visible 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 seven sporadic meteors per hour during the last 
hour before dawn as seen from rural observing sites. Evening rates would be near three per hour. As seen from the mid-southern 
hemisphere (45S), morning rates would be near eight per hour as seen from rural observing sites and three per hour during the 
evening hours. Locations between these two extremes would see activity between the listed figures. Moonlight reduces sporadic rates 
as seen during the morning hours this week.

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

Alpha Capricornids (CAP) - 20:30 (307) -09   Velocity - 25km/sec.
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 3 per hr.

Antihelion (ANT) - 21:00 (315) -15   Velocity - 30km/sec.
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 3 per hr.

Delta Aquariids (SDA) - 22:48 (342) -16    Velocity - 42km/sec.
Northern Hemisphere - 3 per hr.   Southern Hemisphere - 5 per hr.

August Piscids (AUP) - 00:30 (008) +18    Velocity - 66km/sec.
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr.

Perseids (PER) - 00:44 (011) +51    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