During this period the moon reaches its new phase on Friday July 1st. At this time the moon will lie near the sun and will not be visible in the night sky. This weekend the waning crescent moon will not cause problems observing meteors as long as it is kept out of the observers field of view. The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and four as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near seven from the northern hemisphere and eleven as seen from south of the equator. 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 are slightly reduced due to moonlight during this period.
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 25/26. 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:
A few June Bootids (JBO) may be seen during the evening hours 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. Rates at this time should 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 30th. The radiant position at maximum is located at 17:44 (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 should 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 wide Antihelion (ANT) radiant is now centered at 19:08 (287) -22. This area of the sky lies in northern Sagittarius near the fourth magnitude star Omicron Sagittarii. This radiant is best placed near 0200 local daylight time (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 southeastern Ophiuchus, Sagittarius, Scutum, or Serpens Cauda could be a candidate for this shower. Rates at this time should be near two per hour as seen from the northern hemisphere and three 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.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately five sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near eight per hour as seen from rural observing sites and three per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are slightly 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.
|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)||–||14:56 (224) +48||18||22:00||<1 – <1||III|
|f-ophiuchids (FOP)||–||17:44 (266) +09||21||01:00||<1 – <1||IV|
|Antihelions (ANT)||–||18:16 (274) -23||30||02:00||2 – 3||II|