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During this period, the moon reaches its full phase on Thursday July 10th. At that time the moon will be located opposite the sun and will lie above the horizon all night long. This weekend the waxing gibbous moon will set during the morning hours allowing a small window of opportunity to view meteor activity under dark skies between moon set and dawn. The estimated total hourly rates for evening observers this weekend should be near 2 as seen from mid-northern latitudes (45N) and 3 as seen from tropical southern locations (25S). For morning observers, the estimated total hourly rates should be near 4 as seen from mid-northern latitudes (45N) and 5 as seen from tropical southern locations (25S). The actual rates seen will also depend on factors such as personal light and motion perception, local weather conditions, alertness, and experience in watching meteor activity. 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 brighter 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 July 5/6. These positions do not change greatly day to day so the listed positions may be used during this entire period. Most star atlases (available online and at bookstores 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. I have also included charts of the sky that display the radiant positions for evening, midnight, and morning. The center of each chart is the sky directly overhead at the appropriate hour. These charts are oriented for facing south but can be used for any direction by rotating the charts to the desired direction. 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 (culmination), either due north or south along the meridian, depending on your latitude. Radiants that rise after midnight will not reach their highest point in the sky until daylight. For these radiants, it is best to view them during the last few hours before dawn. It must be remembered that meteor activity is rarely seen at its radiant position. Rather they shoot outwards from the radiant, so it is best to center your field of view so that the radiant lies toward 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 sporadic. Meteor activity is not seen from radiants that are located far 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

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The alpha Capricornids (CAP) are active from July 3 through August 13, peaking on July 31st. The radiant is currently located at 19:04 (286) -15. This position lies in northeastern Sagittarius, 3 degrees northwest of the 4th magnitude star known as Rho¹ Sagittarii. Current rates are expected to be less than 1 per hour no matter your location. These meteors are best seen near 01:00 Local Summer Time (LST), when the radiant lies highest in the southern sky. With an entry velocity of 23 km/sec., the average meteor from this source would be of medium-slow velocity.

The large Anthelion (ANT) radiant is currently centered at 19:48 (297) -20. This position lies in eastern Sagittarius, 1 degree south of the faint star known as 58 Sagittarii. This radiant is best placed near 01:00 LST when it lies on the meridian and is highest in the southern sky. Rates at this time should be less than 1 per hour as seen from the northern hemisphere and 1 per hour as seen from south of the equator. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of medium-slow velocity.

The July Pegasids (JPE) are active from July 4-14 with maximum activity occurring on July 10th. The radiant is currently located at 22:52 (343) +10. This area of the sky is located in southern Pegasus, near the faint star known as sigma Pegasi. This radiant is best seen during the last dark hour of the night when the radiant lies highest in the southern sky.  Rates are expected to be near than 1 per hour this week no matter your location. With an entry velocity of 63 km/sec., the average meteor from this source would be of swift velocity.

Sporadic meteors are those meteors that cannot be associated with any known meteor shower. All meteor showers are evolving and disperse over time to the point where they are no longer recognizable. Away from the peaks of the major annual showers, these sporadic meteors make up the bulk of the activity seen each night. As seen from the mid-northern hemisphere (45N) one would expect to see during this period approximately 4 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 1 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 4 per hour as seen from rural observing sites and 1 per hour during the evening hours. Locations between these two extremes would see activity between these listed figures.  Rates are reduced due to moonlight.

The list below offers information in tabular form. Rates and positions in the table are exact for Saturday night/Sunday morning.

Class Explanation: A scale to group meteor showers by their intensity:

• Class I: the strongest annual showers with Zenith Hourly Rates normally ten or better.
• Class II: reliable minor showers with ZHR’s normally two to ten.
• Class III: showers that do not provide annual activity. These showers are rarely active yet have the potential to produce a major display on occasion.
• Class IV: weak minor showers with ZHR’s rarely exceeding two. The study of these showers is best left to experienced observers who use plotting and angular velocity estimates to determine shower association. These weak showers are also good targets for video and photographic work. Observers with less experience are urged to limit their shower associations to showers with a rating of I to III.
  

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Ray Whyte

‘Going dark’