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Post: 12 maja 2018, 05:57 
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During this period the moon will reach it's new phase on Tuesday May 15th. At that time the moon will be located near the sun and will be invisible at night. This weekend the waning crescent moon will rise shortly before dawn and will be too thin to cause any problems viewing meteor activity. The estimated total hourly meteor rates for evening observers this week is 3 as seen from mid-northern latitude (45N) and 4 from the southern tropics (25S). For morning observers the estimated total hourly rates should be near 8 as seen from mid-northern latitudes (45N) and 15 from the southern tropics (25S). 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. 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 May 12/13 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 near 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 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.

The tau Herculids (TAH) are an irregular shower not active every year. They are best known for being associated with comet Schwassmann-Wachmann 3 and the strong display seen in 1930. Due to recent activity from the comet, this shower could produce more activity in the upcoming decade. The Earth could start encountering particles from Schwassmann-Wachmann 3 around May 14. On that date the radiant would lie near 14:24 (216) +35. This area of the sky is located in western Bootes, 4 degrees southwest of the 3rd magnitude star known as Seginus (gamma Bootis). This is not that close to the star tau Herculis, for which this shower is named. Apparently the discoverers of this display placed the radiant further east toward Corona Borealis and Hercules. This area of the sky is best placed near midnight local summer time (LST), when it lies high overhead for observers located in mid-northern latitudes.

The center of the large Anthelion (ANT) radiant is currently located at 16:20 (245) -22. This position lies in northwestern Scorpius, 6 degrees northwest of the bright orange star known as Antares (alpha Scorpii). Due to the large size of this radiant, Anthelion activity may also appear from southern Ophiuchus and Libra as well as Scorpius. This radiant is best placed near 0200 LST, when it lies on the meridian and is located highest in the sky. Rates at this time should be near 2 per hour as seen from mid-northern latitudes and 3 per hour as seen from latitude 25 S. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

The theta 2 Sagittariids (TTS) are a new discovery of the IMO video network using cameras located in Australia. These meteors are active from May 9-14, which maximum activity occurring on the 13th. The radiant lies near the position of 20:04 (301) -33. This area of the sky lies in a rather blank area of southeastern Sagittarius, 2 degrees north of the 4th magnitude star known as theta 2 Sagittarii. The radiant is best placed just before the break of dawn when the radiant lies highest in the sky. While Theta 2 Sagittariid meteors can be seen in both hemispheres, the south is favored as the radiant lies higher in their sky. Hourly rates are expected to be less than 1 no matter your location. At 67km/sec. the Theta 2 Sagittariids would produce meteors of swift velocity.

The eta Aquariids (ETA) are active from a radiant located at 22:56 (344) +01. This area of the sky is located in western Pisces, directly between the pair of 4th magnitude stars known as gamma Piscium and eta Aquarii. These meteors cannot be seen prior to 0200 as the radiant lies below the horizon. The best time to view this activity is during the hour before the start of morning twilight, when the radiant lies highest in a dark sky. Current rates would be near 3 per hour as seen from the northern hemisphere and 5 per hours as seen south of the equator. With an entry velocity of 66 kilometers per second, a majority of these meteors will appear to move swiftly with a high percentage of the bright meteors leaving persistent trains. Surprisingly, this shower produces very few fireballs.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 3 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 2 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 7 per hour as seen from rural observing sites and 3 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are reduced during this period due to moonlight.
RA (RA in Deg.) DEC Km/Sec Local Summer Time North-South
tau Herculids (TAH) Jun 02 14:24 (216) +35 15 00:00 <1 - <1 III
Anthelion (ANT) - 16:20 (245) -22 30 02:00 2 - 3 II
theta 2 Sagittariids (TTS) May 13 20:04 (301) -33 67 05:00 <1 - <1 IV
eta Aquariids (ETA) May 07 22:56 (344) +01 66 08:00 3 - 5 I
Zgodnie z:
Robert Lunsford

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