During July observers in the northern hemisphere witness a surge in meteor activity, especially during the second half of the month. The source of this increase is increased sporadic rates along with several showers located opposite the sun. The Perseids also become active in mid-July with increasing rates as the Earth nears the August 12 maximum. During the first week of the month, observers south of the equator are enjoying some of their best rates of the year. This activity is produced by the strongest sporadic rates of the year and the fact that the Antihelion radiant is positioned well south of the celestial equator this time of year. During the second half of the month the sporadic rates begin to plummet and are the equal of rates seen in the northern hemisphere by the end of the month.
This week the moon will reach its first quarter phase on Monday July 3rd. This weekend the moon will set near midnight local daylight time and will not interfere with meteor observing during the active morning hours. As the week progresses the waxing gibbous moon will pose more of a problem as it intrudes into the morning sky. The estimated total hourly 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 for those in the northern hemisphere and twenty for those south of the equator. These rates assume that you are watching from rural areas away from all sources of light pollution. 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 positions listed below are exact for Saturday night/Sunday morning July 1/2. 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. 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 June Bootids (JBO) are active this week from a radiant located at 15:04 (226) +46. This area of the sky is located in northern Bootes some fifteen degrees southeast of Alkaid (Eta Ursae Majoris), the last star in the handle of the “Big Dipper”. Due to the northern declination this shower is well seen only from the southern equatorial areas northward to the northern temperate areas. Those located north of 50 degrees north latitude will have difficulty seeing any activity due to the very short nights experienced in those latitudes this time of year. This area of the sky is best placed as soon as it gets dark during the evening hours. Peak rates were expected on June 27 so current rates will most likely be quite low. At 18 km/sec. any June Bootids will appear to move quite slowly compared to most meteors.
The Antihelion (ANT) radiant is now centered at 19:32 (293) -20. This area of the sky is located in eastern Sagittarius, five degrees northeast of the third magnitude star Pi Sagittarii. This radiant is best placed near 0200 local daylight time when it lies on the meridian and is highest in the sky. Rates at this time should be near two per hour for those north of the equator and three per hour south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.
After six months of declining rates the Sporadic rates for the Northern Hemisphere are now finally starting to increase. One would expect to see perhaps eight random meteors during the last hour before dawn from rural observing sites. During the first dark hour after the end of evening twilight, perhaps two random meteors can be seen per hour. Sporadic rates increase as the night progresses so rates seen near midnight would be near five per hour. Sporadic rates seen from the southern hemisphere have now reached a secondary maximum. One would see approximately seventeen random meteors per hour during the last hour before dawn and three per hour during the first dark hour after the end of evening twilight. Rates near midnight would be near ten per hour. Evening rates are reduced due to moonlight.