During this period the moon reaches its first quarter phase on Tuesday the 26th. At this time the moon will be located ninety degrees west of the sun and will set between midnight and 0100 for observers located in mid-northern latitudes. This weekend the waxing crescent moon will set during the late evening hours and will be long gone by the time the more active morning hours arrive. The estimated total hourly meteor rates for evening observers this week is near two for observers in the northern hemisphere and three for those south of the equator. For morning observers the estimated total hourly rates should be near ten as seen from mid-northern latitudes and fourteen 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. 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 June 23/24. 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 radiants are expected to be active this week:
A few June Bootids (JBO) may be seen during the evening hours this week radiating from a position near 14:56 (224) +48. This area of the sky lies in northern Bootes, seven degrees north of the fourth magnitude star Beta Bootis. This radiant is best placed as soon as it becomes dark. Hourly rates at this time are expected be less than one for those located in the northern hemisphere and near zero for observers south of the equator. With an entry velocity of 18 km/sec., the average June Bootid meteor would be of very slow speed.
Studies by Sirko Molau and Juergen Rendtel of the IMO’s video data has revealed an active radiant located in Ophiuchus this time of year. The f-Ophiuchids (FOP) are only active from June 27th through July 1, with maximum activity occurring on June 29th. The radiant position at maximum is located at 17:46 (266) +09. This area of the sky lies in northern Ophiuchus, four degrees southeast of the second magnitude star Ras Alhague (Alpha Ophiuchi). This radiant is best placed near 0100 local daylight time (LDT), when it lies on the meridian and is located highest in the sky. Rates at this time are expected to be less than one no matter your location. With an entry velocity of 21 km/sec., the average f-Ophiuchid meteor would be of slow speed.
The large Antihelion (ANT) radiant is currently located at 19:00 (285) -22. This position lies in central Sagittarius, near the group of third and fourth magnitude stars known asÂ Xi, Omicron and Pi Sagittarii. Due to the large size of this radiant, Antihelion activity may also appear from eastern Scorpius, southeastern Ophiuchus, Serpens Cauda, Corona Australis, southern Aquila, western Capricornus, and Scutum as well as Sagittarius. This 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 two per hour as seen from the northern hemisphere and three as seen from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.
Another active radiant in Pisces has been found by Sirko Molau and Juergen Rendtel using the IMO’s video data. The Delta Piscids (DPI) are only active from June 20th through the 24th with maximum activity occurring on the 23th. The radiant position at maximum is located at 00:44 (011) +06. This area of the sky lies in south-central Pisces, just southwest of the fourth magnitude star Delta Piscium. This radiant is best placed just before dawn when the radiant lies highest in a dark sky. Rates, even at maximum activity, are expected to be less than one per hour no matter your location. With an entry velocity of 71 km/sec., the average delta Piscid meteor would be swift.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately seven 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 ten 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 table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning unless the showers are of short duration. In that case the position on the night of maximum activity is listed.
|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|
|June Bootids (JBO)||June 27||14:56 (224) +48||18||22:00||<1 – <1||III|
|f-Ophiuchids (FOP)||June 29||17:46 (266) +09||21||01:00||<1 – <1||IV|
|Antihelions (ANT)||–||19:00 (285) -22||30||02:00||2 – 3||II|
|Delta Piscids (DPI)||June 23||00:44 (011) +06||71||08:00||<1 – <1||IV|