Meteor Activity Outlook for May 12-19, 2012

During this period the moon reaches its last quarter phase on Saturday the 12th.
At this time the moon will be located ninety degrees west of the sun and will
rise near 0100 local daylight time (LDT). As the week progresses the waning
crescent moon will rise later in the morning, increasing the window of
opportunity to view in totally dark conditions. The estimated total hourly rates
for evening observers this week is near three for observers in the northern
hemisphere and four for those south of the equator. For morning observers the
estimated total hourly rates should be near nine as seen from mid-northern
latitudes and fifteen from mid-southern latitudes. 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. Morning rates
are reduced slightly due to moonlight during this period.

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 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 showers are expected to be active this week:

The large Antihelion (ANT) radiant is currently located at 16:16 (244) -21.
This position lies in northwestern Scorpius, six degrees northwest of the bright
first magnitude orange star Antares (Alpha Scorpii). Due to the large size of
this radiant, Antihelion activity may also appear from western Ophiuchus, Libra,
northern Lupus, as well as Scorpius. This radiant is best placed near 0200 LDT,
when it lies on the meridian and is located highest in the sky. Rates at this
time should be near one per hour as seen from the northern hemisphere and two as
seen from south of the equator. With an entry velocity of 30 km/sec., the
average Antihelion meteor would be of slow velocity.

The last of the Eta Lyrids (ELY) are visible this weekend from a radiant located
at 19:23 (292) +43. This position lies in extreme eastern Lyra, four degrees
southwest of the third magnitude star Delta Cygni. This shower is active from
May 6 through the 14th and peaked on May 11. Rates at maximum activity are near
two per hour as seen from the northern hemisphere. Unfortunately the Eta Lyrid
radiant does not rise very high in the northern sky as seen from the southern
hemisphere so rates seen from below the equator are minimal. Activity from this
shower is best seen during the last hour before dawn when the radiant is
situated highest in a dark sky. With an entry velocity of 43 km/sec., the
average Eta Lyrid meteor would be of medium speed.

The Eta Aquariids (ETA) are particles from Halleys Comet, produced in
Earth-crossing orbits many centuries ago. We pass closest to these orbits from
May 5 through the 9th. During this period the Eta Aquariids are at their best,
capable of producing ZHRs of sixty. The actual visible rates are most often less
than half this figure due to the low altitude of the radiant at dawn. Observed
hourly rates at maximum normally vary from zero at 60 degrees north latitude to
30 near the equator and back down to near zero again in Antarctica, where the
radiant elevation is again very low. Hourly rates this weekend will most likely
be less than five per hour. Rates will slowly decrease as the week progresses as
we move further from the May 7 maximum. The radiant is currently located at
22:52 (343) +01. This area of the sky is located on the Aquarius/Pisces border,
three degrees east of the fourth magnitude star Eta Aquarii. 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. With
the moon now in the morning eastern sky, it would be best to face either due
north or due south, just enough to keep the moon out of your field of view. With
an entry velocity of 67 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 four sporadic meteors per hour during the last hour before dawn as
seen from rural observing sites. Evening rates would be near two per hour. As
seen from the mid-southern hemisphere (45S), morning rates would be near eight
per hour as seen from rural observing sites and three per hour during the
evening hours. Locations between these two extremes would see activity between
the listed figures. Morning rates are reduced due to moonlight.

The table below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning.