During this period the moon reaches its first quarter phase on Sunday April 6th. At this time the moon will lie 90 degrees east of the sun and will set near 0200 local daylight time (LDT) as seen from mid-northern latitudes. As the week progresses the waxing gibbous moon will begin to interfere with meteor observing as it remains in the sky most of the night. The estimated total hourly meteor rates for evening observers this week is near 2 for observers situated at mid-northern latitudes and 3 for observers viewing from the southern tropics (latitude 25 S.). For morning observers the estimated total hourly rates should be near 9 for observers situated at mid-northern latitudes and 12 for observers viewing from the southern tropics. 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 during this period due to interfering 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 brightest 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 April 5/6. 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 sources of meteoric activity are expected to be active this week:
The center of the large Anthelion (ANT) radiant is currently located at 13:56 (209) -11. This position lies in southeastern Virgo, 5 degrees east of the 1st magnitude star known as Spica (Alpha Virginis). These meteors may be seen all night long but the radiant is best placed near 0200 LDT when it lies on the meridian and is positioned highest in the sky. Due to the large radiant area, meteors from this source may also appear to radiant from the constellation of Corvus, Libra, and eastern Hydra, Rates at this time should be near 2 per hour no matter your location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.
The Zeta Cygnids (ZCY) are active from a radiant near the position of 19:52 (298) +40. This position lies in western Cygnus, 5 degrees south of the 3rd magnitude star know as Rukh (Delta Cygni). This position is best suited for viewing from the northern hemisphere where the radiant lies high in the northeastern sky during the last couple of hours before dawn. During the same time of night, as seen from the southern tropics, the radiant lies low in the northeast therefore diminished activity will be seen from the southern hemisphere. This source peaks on April 6th when perhaps 2 shower members may be seen per hour when the radiant is located high in the sky. These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. At 43 km/sec. these meteors would have a medium velocity.
The Delta Aquiliids (DAL) are active from April 5 through through the 13th, with maximum activity occurring on the morning of 11th. This stream was first noticed by Peter Jenniskens and is mentioned in his book Meteor Showers and their Parent Comets. It has been recently verified in the IMO video database producing low activity during the period mentioned above. The radiant is currently located near 20:24 (306) +11. This position actually lies in southwestern Delphinus, two degrees west of fourth magnitude star Epsilon Delphini. The radiant is best placed in a dark sky just before dawn. Rates are expected to be less than one per hour, even at maximum activity. At 66km/sec. this shower would produce meteors of swift velocity.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately 5 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 8 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.
The table below presents a list of radiants that are expected to be active this week. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.
|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|
|Anthelions (ANT)||–||13:56 (209) -11||29||02:00||2 – 2||II|
|Zeta Cygnids (ZCY)||Apr 08||19:20 (290) +38||43||08:00||2 – <1||IV|
|Delta Aquiliids (DAL)||Apr 11||20:24 (306) +11||66||09:00||<1 – <1||IV|