(meteorobs) Meteor Activity Outlook for May 22-28, 2010

[Robert Lunsford]

May is a fairly slow month for meteor activity. The Eta Aquariids are very active the first two weeks of the month then fade as the 
month progresses. The only other showers active this month are the weak Nu Cygnids, the Eta Lyrids, and the Antihelion radiant. 
These will add only 1-2 meteors per hour to the total count. Sporadic rates are low but steady 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 full phase on Thursday May 27th. At this time the moon lies opposite of the the sun and is 
in the sky the entire night. Conditions are more favorable this weekend as the waxing gibbous moon will set during the early morning 
hours allowing a couple hours of darkness between moonset and the start of morning twilight. The estimated total hourly rates for 
evening observers this week is near one for northern observers and two for those viewing from south of the equator. For morning 
observers the estimated total hourly rates should be near seven from the northern hemisphere and seventeen 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 reduced 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 May 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 wide Antihelion (ANT) radiant is now centered at 16:56 (254) -23. This area of the sky lies in southern Ophiuchus some seven 
degrees northeast of the first magnitude orange star Antares (Alpha Scorpii). 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 eastern Libra, northern Lupus, southern Ophiuchus, southern Serpens Cauda, western Sagittarius, or Scorpius could be 
a candidate for this shower. Rates at this time should be near one per hour as seen from the northern hemisphere and two 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.

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

Antihelion (ANT) - 16:56 (254) -23   Velocity - 30km/sec.
Northern Hemisphere - 1 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