Meteor Activity Outlook for September 14-20, 2007

September offers longer nights and cooler temperatures in the northern hemisphere. In the sky no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. The two recognized minor showers active in early September have high northern declinations (celestial latitude) therefore are much better suited to be viewed from locations north of the equator. Toward the end of the month the antihelion radiant becomes entangled with the two Taurid radiants and is impossible to separate. Therefore the antihelion radiant will be excluded from the list until the end of the Taurid activity period late in November. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Taurid radiants are not too badly placed so observers south of the equator can expect to see a little of this activity toward the end of the month.

During this period the moon reaches its first quarter phase on Wednesday September 19. At this time the moon is located ninety degrees east of the sun and sets near 0100 local daylight time. The estimated total hourly rates for evening observers this week is near three for those located north of the equator and one for observers south of the equator. For morning observers the estimated total hourly rates should be near sixteen for those located in the northern hemisphere and six for those viewing from south of the equator. These rates assume that you are watching from rural areas away from all sources of light pollution. 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 positions and rates listed below are exact for Saturday night/Sunday morning September 15/16. 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 Antihelion (ANT) radiant is now centered at 00:24 (006) +03. This area of the sky is located in a southern Pisces, seven degrees southwest of the fourth magnitude star Delta Piscium. 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 two per hour regardless of your location. With an entry velocity of 30 km/sec., the average antihelion meteor would be of medium-slow speed.

The September Perseids (SPE) peaked on the morning of September 9 and reaches a ZHR of one on the 17th. The radiant is located at 04:28 (067) +48, which places it in eastern Perseus, two degrees southeast of the fourth magnitude star Mu Persei. The radiant is best placed in the sky just before the start of morning twilight, when it lies highest above the horizon. At 64km/sec., the average September Perseid is swift.

As activity from the September Perseids wanes the Delta Aurigids (DAU) take their place. While not as active as the September Perseids, the Delta Aurigids are present in the morning skies in the second half of September and early October. Maximum activity occurs on October 4 with a average ZHR of two. Current rates will be most likely less than one per hour. This shower shares the same radiant as the September Perseids so any activity onward from September 18 should be associated with the Delta Aurigids. At 64km/sec., the average Delta Aurigid is swift.

Sirko Molau's study of the IMO's video database has led to the discovery of an active radiant in Lynx this week. The shower peaks on September 13 from a radiant located at 07:36 (114) +56. The radiant is best placed just before the start of morning twilight when it lies highest in a dark sky. Current rates would most likely be less than one per hour, but this is uncertain. With an entry velocity of 53km/sec., activity from this radiant would be of medium-swift velocity.

Sporadic rates are slowly rising for observers in the northern hemisphere and falling steadily for those located south of the equator. One would expect to see approximately fourteen random meteors during the last hour before dawn from rural observing sites in the northern hemisphere. During the first dark hour after the end of evening twilight, perhaps three random meteors can be seen per hour. As seen from the southern hemisphere late morning rates would now be near four per hour. During the first dark hour after the end of evening twilight, perhaps one random meteor can be seen per hour. Evening rates are reduced due to moonlight.