(meteorobs) Meteor Activity Outlook for April 11-17, 2008

[Robert Lunsford]

Meteor activity picks up a bit during April as two major showers are
active during the month. The first of these, the Lyrids, are active from the
16th through the 25th, with a pronounced maximum on the 22nd. Unfortunately
this date coincides with a full moon this year so activity will be reduced.
The Eta Aquarids start appearing near the 20th and reach maximum activity
during the first week in May. 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) rise this month toward a maximum in July.

During this period the moon reaches its first quarter phase on Saturday
April 12th. At this time the moon will be located ninety degree east of the
sun and will set near 0100 daylight time. With the moon situated well north
of the celestial equator at this time, moonset will occur substantially
later for observers at high northern latitudes and substantially earlier for
high southern latitudes. Next week the waxing gibbous moon will set later in
the morning limiting the time observers can view under dark skies. 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 nine. For those located in the
mid-southern hemisphere (45 S) morning rates would be near fifteen 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 by moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning April 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 wide Antihelion (ANT) radiant is now centered at 14:24 (216) -14. This
area of the sky lies on the Virgo/Libra border near the faint star lambda
Virginis. This radiant is best placed near 0200 LDT time when it lies on the
meridian and is highest in the sky. Actually any meteor from southern Virgo
or western Libra could be a candidate for this shower. Rates at this time
should be near two per hour no matter your location. With an entry velocity
of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.

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 thirteen per hour as seen from
rural observing sites and two per hour during the evening hours. Evening
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.

Antihelion (ANT) - 14:24 (216) -14   Velocity - 30km/sec.
Northern Hemisphere - 2   Southern Hemisphere - 2

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2008

Clear Skies!
Robert Lunsford
American Meteor Society