Meteor Activity Outlook for May 1-7, 2010

May is a fairly slow month for meteor activity.
The Eta Aquariids are very active the first two weeks of the month then fade as
the month progresses. The only other showers active this month are the weak Nu
Cygnids, the Eta Lyrids, and the Antihelion radiant. These will add only 1-2
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 last quarter
phase on Wednesday 6th. At this time the moon lies ninety degrees west of the sun
and rises near 0100 local daylight time (LDT). This weekend the waning gibbous moon
will rise during the late evening hours, effectively ruining your chance of seeing
good meteor activity the remainder of the night. Conditions improve slightly with
each passing night as the moon’s phase lessens and it rises later and later. The
estimated total hourly rates for evening observers this week is near two for
northern observers and three for those viewing from south of the equator. For
morning observers the estimated total hourly rates should be near seven from the
northern hemisphere and twelve as seen from the southern hemisphere. 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 due to moonlight.

The radiant positions and rates listed below are exact
for Saturday night/Sunday morning May 1/2. 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 wide Antihelion (ANT) radiant is now centered at 15:36 (234) -19. This
area of the sky lies in eastern Libra, seven degrees northwest of the second
magnitude star Dschubba (Delta Scorpii). This radiant is best placed near 0200
local daylight time (LDT) when it lies on the meridian and is located highest in
the sky. Due to the large size of this radiant, any meteor radiating from extreme
eastern Hydra, Libra, northern Lupus, or western Scorpius could be a candidate
for this shower. Rates at this time should be near one per hour as seen from the
northern hemisphere and two per hour as seen from south of the equator. With an
entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow
speed.

The team of Sirko Molau and Juergen Rendtel have discovered a weak radiant active
at this time in the constellation of Cygnus. Video data shows that the Nu
Cygnids (NCY) are active from April 18th through May 7th. Maximum activity
occurred on the morning of April 20th. The radiant is currently located at
21:48 (327) +48. This position lies in northeastern Cygnus close to the faint
star known as Pi 2 Cygni. The radiant is best placed during the last dark hour
before dawn, when it lies highest above the horizon in a dark sky. At 42km/sec.
the Nu Cygnids would produce meteors of medium velocity. Expected rates are less
than one per hour. Due to the northerly declination of the radiant, these meteors
are not well seen from south of the equator.

The Eta Aquariids (ETA) are particles from Halley’s 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 ZHR’s 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
25 near the equator and back down to near zero again in Antarctica, where the
radiant elevation is very low. Hourly rates this weekend are anywhere from zero
to five per hour depending on your latitude and observing conditions. Rates will
increase significantly as the week progresses as we approach the May 7 maximum.
The radiant is currently located at 22:24 (336) -02. This area of the sky is
located in northern Aquarius, just south of the fourth magnitude star Gamma 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
down toward the eastern horizon. 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 one per hour. As seen from the
mid-southern hemisphere (45S), morning rates would be near seven per hour as seen
from rural observing sites and two 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.