Meteor Activity Outlook for August 21-27, 2010

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 full phase on Tuesday August 24th. At this time the moon will be located opposite the sun and will be in the sky all night long. This weekend the waxing gibbous moon will set near the start of morning twilight, depending on your latitude. The further north one is located, the earlier the moon will set, allowing more time to observe under dark skies. The estimated total hourly rates for evening observers this week is near two no matter your location. For morning observers the estimated total hourly rates should be near eight from the northern hemisphere and six 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. Rates are reduced this week due to intense 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 21/22. 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 table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.

The detailed descriptions will be continued next week when the moonlight is not as intense.

SHOWER DATE OF MAXIMUM ACTIVITY CELESTIAL POSITION ENTRY VELOCITY CULMINATION HOURLY RATE CLASS*
    RA (RA in Deg.) DEC Km/Sec Local Daylight Time North-South  
             
August Draconids (AUG) Aug 21 18:28 (277) +63 23 22:00 <1 - <1 IV
Antihelion (ANT) - 22:48 (342) -06 30 02:00 1 - 1 II
Delta Aquariids (SDA) Jul 30 00:01 (000) -10 42 03:00 <1 - <1 I
Perseids (PER) Aug 13 04:04 (061) +60 61 06:00 1 - <1 I