This week may well be one of the most active of the summer
as several showers in the Aquarius/Capricornus region reach maximum
activity plus the Perseids
are still gaining strength. The moon is new on Monday July 31
and will not be a factor at all in either the morning or evening
sky. The next new moon period in August will offer much less activity
so I would suggest watching this week's offerings and enjoying
the balmy nighttime temperatures before they slip away. All positions
are exact for Saturday night/Sunday morning July 29/30. The positions
do not change greatly day to day so these positions may be used
during this entire period.
Editor's note: The paragraphs below describe the locations of meteor shower radiants (points in the sky from which meteors appear to stream). For example, a radiant located at "01:56 (029) +55" corresponds to Right Ascension = 1h56m and declination = +55o. The number in parentheses is the Right Ascension in degrees.
If you are facing south and concentrating on the many minor shower coming from that portion of the sky (described below), you may often notice a swift meteor coming from the northeast shooting into your field of view. Most likely these are early Perseids from a radiant on the Perseus/Cassiopeia border located at 01:56 (029) +55. Perseid rates were surprisingly good on July 26 so expect to see up to 5 shower members each hour during this period. The Perseids are best seen just before dawn when the radiant is high in the northeastern sky. Perseid meteors are swift and noted for their many persistent trains and colorful meteors. Finally the hourly sporadic rates during the evening hours should be near 5 while those in the morning should be between 10 and 15.
The Alpha Capricornids will provide the evening's first target. On Saturday evening the radiant will be located at 20:32 (308) -10, which is just northeast of the wide naked eye double star Alpha Capricornii, in the northwest of this constellation. The radiant is active during the late evening hours but is best placed for observing near 0100, when it lies on the meridian (due south). Alpha Capricornid rates can be quite variable ranging from 0 to 5 per hour. While most shower members are faint there is an occasional colorful fireball, often fragmenting as it streaks in the heavens above.
The Antihelion radiant is located at 21:24 (321) -14. This position lies in northeastern Capricornus near the 4th magnitude star Iota Capricornii. With the South Iota Aquarids now active the anthelion now covers portions of two other radiants, the South Iota Aquarids and the North Delta Aquarids. The NDA's are a bit faster which could help in determining shower association. The SIA's are probably a portion of the anthelion activity as the position and velocity is similar. It would be hopeless to try to separate the anthelion radiant with plotting, photography, or video. This week I would suggest including any antihelion suspects in with the South Iota Aquarids. These meteors appear to move slowly in the sky, averaging 5 degrees per second, depending on their distance from the radiant and the elevation above the horizon.
The North Delta Aquarid radiant lies at 21:48 (327) -08. This position lies just east of the 3rd magnitude star Beta Aquarii. The North Delta Aquarids are of medium speed and usually faint. They are best seen near 0200 this time of year. The NDA's do not peak until August 8 so rates will most likely be less than 1 per hour this week. As stated above, be careful with shower association as the radiant is quite close to the antihelion and South Iota Aquarid radiants.
The South Iota Aquarids are active from a radiant located at 21:52 (328) -16. This position is very close to the 3rd magnitude star Delta Capricorni in eastern Capricornus. This shower will reach maximum activity on August 4 so rates would most likely be less than 1 per hour this week. Any rates higher than this would be most likely caused by the additional activity from the nearby antihelion radiant. These meteors are slow which will could help separate them from the North Delta Aquarids.
The South Delta Aquarid radiant lies at 22:40 (340) -16. This position is just west of the 3rd magnitude stars Delta and 71 Aquarii. The shower was predicted to peak on July 27 but rates seen on the 26th were quite low. The actual peak may occur on the 28th or 29th. This shower has the potential of producing 25 meteors per hour as seen from temperate locations. This would be far and away the strongest radiant in the sky at this time. What actually occurs will be anyone's guess! The South Delta Aquarids are of medium speed and normally do not produce persistent trains. The radiant is best placed between 0200-0300 when it culminates in the southern sky.
The Pisces Austrinid radiant is located at 22:52 (343) -29, very close to the bright star Fomalhaut. Like the Alpha Capricornids, activity from this radiant can be quite variable. Rates can appear as high a 3 shower members per hour or as low as none the entire night. 1999 was a good year for this radiant and hopefully 2000 will be similar. Like most of the radiants in this area, these meteors are of medium speed and usually on the faint side. Surprisingly, shower members seen on July 26 were bright. Lying just south of the South Delta Aquarids, this radiant also culminates between 0200-0300.
The two branches of the Apex source lie at 02:24 (036) +29 and 02:24 (036) -01. During one year back in the late 1970's, veteran meteor observer Felix Martinez observed on nearly every night during the last half of July and the first half of August. Although the moon was a factor during some of this period, some valuable data was obtained. from his efforts. Felix detected a radiant on the Pisces/Aries border which was active on many nights. I believe that this activity could very well have been from the northern branch of the apex. This week northern branch is located in Triangulum very close to the position of Felix's radiant. The southern branch is located in Cetus, just northeast of the famous variable star Mira. These two radiants are best placed just before dawn and should provide 2-3 swift meteors per hour streaking through the morning sky. Be sure sure to keep an eye out for this activity while you watch this week!