During this period the moon reaches its last quarter phase on Tuesday September 16th. At this time the moon is located 90 degrees west of the sun and rises near midnight local daylight time (LDT) for observers located in mid-northern latitudes. As the week progresses the moon will continue to wane and will be less of a problem for meteor observers. The estimated total hourly meteor rates for evening observers this week is near 4 as seen from the northern hemisphere and 3 as seen from southern tropical latitudes. For morning observers the estimated total hourly rates should be near 14 for observers located in mid-northern latitudes and 9 for south tropical observers. 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. Morning rates during this period are reduced due to moonlight. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brightest meteors will be visible from such locations.
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 September 13/14. 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.
These sources of meteoric activity are expected to be active this week:
The Southern Taurids (STA) are currently active from a radiant located at 00:56 (014) +04. This position lies in southern Pisces, four degrees south of the fourth magnitude star Delta Piscium. These meteors may be seen all night long but the radiant is best placed near 0200 LDT when it lies on the meridian and is located highest in the sky. Rates at this time should be near one per hour regardless of your location. With an entry velocity of 29 km/sec., the average Southern Taurid meteor would be of slow velocity.
A recently discovered shower with a short duration of only 7 nights are the September Iota Cassiopeiids (SIC). These meteors were discovered by Juergen Rendtel and Sirko Molau while searching for radiants among the data of the IMO video network. This shower is active from September 10th through the 16th with maximum activity occurring on the 14th. At maximum, the radiant lies at 03:04 (046) +64. This position lies in eastern Cassiopeia some 7 degrees east of the 3rd magnitude star known as Segin (Epsilon Cassiopeiae). Rates at maximum are not expected to exceed 1 per hour. Due to the high northern declination (celestial latitude) this shower is poorly seen from the southern hemisphere. With an entry velocity of 55 km/sec., the average September Iota Cassiopeiid meteor would be of swift velocity. This shower may be an outlying member of the Perseus-Auriga complex active this time of year.
The September Epsilon Perseids (SPE) are active from a radiant located at 03:32 (053) +39. This position lies in southern Perseus, 4 degrees southwest of the 3rd magnitude star Epsilon Persei. The radiant is best placed near 0500 LDT, when it lies highest above the horizon. Rates seen from the northern hemisphere should be near 2 per hour during the morning hours. With an entry velocity of 65 km/sec., most activity from this radiant would be swift. This activity is visible from the tropical regions of the southern hemisphere, but further south the radiant becomes too low in the sky to produce much activity.
The September Pi Orionids (POR) are a short duration shower discovered by John Greaves during his studies of video data from the SonotaCo Network in Japan. This shower is only active from September 16-20 with no discernible maximum. The average position of the radiant is 04:08 (062) +06 which places the radiant in southern Taurus between the 4th magnitude stars Nu and Upsilon Tauri. This position is also close to that of the Orionid radiant so care must be taken to differentiate between the two sources. Activity is expected to be low, especially with interference from the moon. This area of the sky is best placed in the sky during the last hour before dawn, when it lies highest above the horizon in a dark sky. These meteor may be seen equally well from both hemispheres. With an entry velocity of 66 km/sec., most activity from this radiant would be swift.
The Orionids (ORI) are active from a radiant at 04:36 (069) +03, which places it on the Taurus/Orion border some 15 degrees south of the bright orange first magnitude star known as Aldebaran (Alpha Tauri). The faint star known as Pi 3 Orionis lies a bit closer, 3 degrees to the northeast but is more difficult to locate. This area of the sky is best placed in the sky during the last hour before dawn, when it lies highest above the horizon in a dark sky. Rates this week would be near 2 per hour no matter your location. With an entry velocity of 67 km/sec., most activity from this radiant would be of swift speed.
Video studies by Molau and Rendtel has revealed a radiant active from September 7th-18th, with maximum activity occurring on the 9th. The current radiant position for the September Lyncids (SLY) is 07:48 (117) +56. This position lies in a remote area of northern Lynx. The nearest star of note is 4th magnitude Omicron Ursae Majoris, which lies 10 degrees to the northeast. This area of the sky is best placed during the last hour before dawn, when it lies highest above the horizon in a dark sky. Rates should be near 1 per hour as seen from the northern hemisphere and near zero from south of the equator. Due to the high northern declination this activity is not well seen south of the equator. With an entry velocity of 60 km/sec., most activity from this radiant would be of swift speed.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately 8 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 3 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 6 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are reduced due to interfering moonlight.
The list below offers the information from above in tabular form. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.
|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|
|Southern Taurids (STA)||Oct 10||00:56 (014) +04||29||02:00||1 – 1||II|
|September Iota Cassiopeiids (SIC)||Sep 14||03:04 (046) +64||55||04:00||<1 – <1||IV|
|September Epsilon Perseids (SPE)||Sep 09||03:36 (054) +39||65||05:00||2 – <1||II|
|September Pi Orionids (POR)||Sep 18||04:08 (062) +06||66||06:00||<1 – <1||IV|
|Orionids (ORI)||Oct 22||04:36 (069) +03||67||06:00||2 – 2||I|
|September Lyncids (SLY)||Sep 09||07:48 (117) +56||60||09:00||1 – <1||IV|