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 Wednesday August 2nd. This weekend the waxing crescent moon will set during the evening hours and will not interfere with morning observing, the time when activity is at its best. As the week progresses the moon will set later and later but will still leave a large window of dark sky between the time of moonset and the start of morning twilight. 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 thirty two for those in the northern
hemisphere and thirty six 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 30/31. 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 Alpha Capricornids (CAP) are active from a wide radiant centered at 20:32 (308) -10. This position lies in northwestern Capricornus, three degrees northeast of the wide third magnitude double star Alpha Capricorni. The radiant is best placed near 0100 local daylight time , when it lies highest in the sky. Current rates would be near two per hour, no matter your location. With an entry velocity of 23 km/sec., most activity from this radiant would be slow. This radiant is well seen except for far northern latitudes where it remains twilight all night long and the radiant does not rise as high into their sky. The Alpha Caps are also known for producing impressive fireballs.
The Antihelion (ANT) radiant is now centered at 21:16 (319) -14. This area of the sky is located in central Capricornus, three degrees northwest of the fourth magnitude star Iota Capricornii. 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.
Please note that commencing in 2007; the International Meteor Organization will suggest that visual observers include the North Delta Aquarids and both branches of the Iota Aquarids as Antihelions.
The Southern Delta Aquarids (SDA) reached maximum activity on July 28, with rates between 10 and 20, depending on your latitude. The radiant is located at 22:40 (340) -16. This position lies in southern Aquarius, three degrees west of the third magnitude star Delta Aquarii. The radiant is best placed near 0300 local daylight time, when it lies highest in the sky. Observers near 20 degrees south latitude are most favored with longer nights and the radiant passing through the zenith. With an entry velocity of 41 km/sec.,
most activity from this radiant would be of average velocities. These meteors tend to be faint so the darkest skies are necessary in order to see this shower well.
The Pisces Austrinids (PAU) also peak on July 28, but are much weaker than the Southern Delta Aquarids. Visual rates rarely exceed three per hour, even where the radiant passes through the zenith. The radiant is located at 22:52
(343) -29. This area of the sky lies just one degree west of the bright star Fomalhaut (Alpha Piscis Austrini). These meteors are best seen near 0300 LDT, when the radiant lies highest above the horizon. These meteors are of average velocity, slower than the Aquarids but faster than the Alpha Caps and the antihelion meteors.
Perseid (PER) activity is now near five per hour, as seen from the northern hemisphere. This rate will slowly increase as we approach the peak on the morning of August 12. The current radiant position lies at 01:56 (029) +54,
which is located in extreme northwestern Perseus, five degrees southwest of the famous “Double Cluster” in Perseus. The radiant is well placed for those in the Northern Hemisphere during the last few hours before dawn. Due to the
high northern declination (celestial latitude) of the radiant, rates seen from the Southern Hemisphere are very low when compared to those seen north of the equator. At 59 km/sec., Perseid meteors are swift, often exhibiting
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 eleven 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 six per hour. Sporadic rates seen from the southern hemisphere have now
reached a secondary maximum and are now starting to fall. One would see approximately twelve 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 eight per hour. Evening rates
are reduced due to moonlight.