During this period the moon reaches its new phase on Monday August 29th. At this time the moon will lie near the sun and will not be visible at night. Next week the waxing crescent moon will enter the evening skies but will set soon after dusk, allowing meteor observers to view under dark conditions during the late night and early morning hours. The estimated total hourly rates for evening observers this week is near six as seen from the northern hemisphere and three as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near fifteen as seen from mid-northern latitudes and seven from mid-southern latitudes. 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.
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 27/28. 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 last of the August Draconids (AUD) will occur this weekend from a radiant located at 18:39 (280) +63. This position lies in southeastern Draco, five degrees southwest of the fourth magnitude star Delta Draconis. Maximum activity occurred on August 21st so rates would be low, less than one per hour at best. With an entry velocity of 23 km/sec. most of these meteors will appear to move slowly. The radiant is best placed near 2200 Local Daylight Time (10pm LDT) when it lies highest in the sky. Due to its high northern declination this shower is not well seen from the southern hemisphere.
The wide Antihelion (ANT) radiant is now centered at 23:08 (347) -04. This area of the sky lies on the Pisces/Aquarius border, twenty degrees south of the second magnitude star Markab (Alpha Pegasi). This radiant is best placed near 0200 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 Aquarius, western Pisces, western Cetus, or southern Pegasus 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.
The Aurigids (AUR) are first seen on August 28 and peak on Thursday morning September 1st. On that morning of maximum activity, the radiant will be located at 06:02 (091) +39. This position lies in central Auriga, two degrees north of the third magnitude Theta Aurigae. The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. Hourly rates this weekend will be very low, less than one per hour no matter your location. At maximum, hourly rates during the last hour before dawn will range from 2-5 as seen from the northern hemisphere. South of the equator, this shower is not well seen as it lies low in the northern sky during the morning hours. With an entry velocity of 67 km/sec., most activity from this radiant would be swift.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately fourteen sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near five per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near five 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.
The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.
|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 (AUD)||Aug 21||18:39 (280) +63||23||22:00||<1 – <1||IV|
|Antihelions (ANT)||–||23:08 (347) -04||30||02:00||1 – 2||II|
|Aurigids (AUR)||Sep 01||06:02 (091) +39||67||09:00||<1 – <1||II|