Meteor Activity Outlook for May 10-16, 2008

May is a fairly slow month for meteor activity.
The Eta Aquariids are very active the first week of the month then fade as the
month progresses. The only other showers active this month are the Eta Lyrids and
the Antihelion radiant. These will add only 2-3 meteors per hour to the total count.
Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N).
Sporadic rates seen from the mid-southern hemisphere (45 S) continue to rise this
month toward a maximum in July.

During this period the moon reaches its first quarter
phase on Monday May 12th. At this time the moon will be located ninety degrees east
of the the sun and will set near 0100 local daylight or summer time (DST). As seen
from the mid-northern hemisphere (45 N) the estimated total hourly rates during the
evening observers would be only one. For morning observers the estimated total hourly
rates should be near twelve. For those located in the mid-southern hemisphere (45 S)
morning rates would be near twenty and evening rates near two. 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 lunar interference.

The radiant positions and rates listed below are exact
for Saturday night/Sunday morning May 10/11. 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 now centered at 16:12 (243) -21. This
area of the sky lies in northwestern Scorpius, seven degrees northwest of the
orange first magnitude star Antares (Alpha Scorpii). Actually any meteor from
northwestern Scorpius, southern Ophiuchus, northern Lupus as well as eastern Libra
could be a candidate for this shower. This radiant is best placed near 0200 LDT
when it lies on the meridian and is highest in the sky. Rates at this time should
be near two for northern observers and three for observers south of the equator.
With an entry velocity of 30 km/sec., the average Antihelion meteor would be of
medium-slow speed.

The Eta Lyrids (ELY) are produced by comet IRAS-Araki-Alcock, which passed
very close to the Earth twenty five years ago this May. Weak activity from
this radiant has been seen in most years from May 3 through May 12, with
maximum activity occurring on May 8. The current radiant position is located
at 19:16 (289) +44. This area of the sky is located in on the Lyra/Cygnus border,
eight degrees northeast of the zero magnitude star Vega (Alpha Lyrae). The best
time to view this activity is just before the start of morning twilight, when the
radiant lies highest in a dark sky. With an entry velocity of 44 kilometers per
second, a majority of these meteors will appear to move at moderate speeds.

The Eta Aquariids (ETA) peaked last week and are now on the declining side
of their activity profile. Rates as high as five per hour could still be seen in
tropical areas during the last dark hour of the night. In other locations hourly
rates of 1-3 can be expected during that same period. Since the radiant lies only
sixty degrees west of the sun, meteors from this shower are not visible prior to
0200 LDT. The radiant is currently located at 22:44 (341) +01. This area of the
sky is located in extreme northern Aquarius, two degrees northeast of the faint
star Eta Aquarii. The best time to view this activity is just before the start of
morning twilight, when the radiant lies highest in a dark sky. No matter your
location these meteors will appear from the eastern sky and shoot in all directions.
If the radiant has sufficient altitude Eta Aquariid meteors can also be seen shooting
downward toward the eastern horizon. 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.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are
low, but fairly steady. One would expect to see approximately seven random meteors
during the last hour before dawn from rural observing sites and only one per hour
during the evening hours. As seen from the mid-southern hemisphere (45S) morning
rates would be near fourteen per hour as seen from rural observing sites and two
per hour during the evening hours. Moonlight interferes slightly during the evening
hours.

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