Meteor Activity Outlook for October 19-25, 2007

Meteor activity in general increases in October
when compared to September. A major shower (the Orionids) is active most of the
month along with several minor showers. Both branches of the Taurids become more
active as the month progresses, providing slow, graceful meteors to the nighttime
scene. The Orionids are the big story of the month reaching maximum activity on
the 21st. This display can be seen equally well from both hemispheres which
definitely helps out in the sporadic-poor southern skies this time of year.

During this period the moon reaches it first
quarter phase on Friday October 19. At this time the moon sets near midnight local
daylight time leaving the prime morning hours free of interfering moonlight. As
the period progresses the window of dark skies shrinks as the moon sets later in
the morning sky. The estimated total hourly rates for evening observers
this week is near three for those located in the mid-northern hemisphere (45 N) and
one for observers from the mid-southern hemisphere (45 S). For morning observers
the estimated total hourly rates should be near fifty for those located in the
mid-northern hemisphere (45 N) and thirty for those viewing from the mid-southern
hemisphere (45 S). 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. Moonlight interferes with evening
rates.

The radiant positions and rates listed below are exact
for Saturday night/Sunday morning October 20/21. 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:

At this time of year debris from comet 2P/Encke produces a double radiant
very close to the position of the antihelion radiant. From now through the
end of November, it is impossible to resolve the antihelion meteors from
those produced by comet 2P/Encke. Therefore we suggest that observers simply
classify meteors from this area as either north or south Taurids. Although
the radiants actually lie in Aries during October, they reach maximum
activity in November when they are situated in the constellation of Taurus.

The Northern Taurid (NTA) radiant is now centered at 02:36 (039) +18. This
position lies in central Aries, eight degrees southeast of the second magnitude star
Hamal (Alpha Arietis). The Southern Taurid (STA) radiant lies at 02:40 (040)
+12. This position lies in southern Aries, two degrees northwest of the
fourth magnitude star Mu Ceti. The two radiants are separated by
slightly over five degrees. Since they have nearly the same right ascension
(celestial longitude), it is difficult to distinguish meteors that move
north or south out of the radiants. It is less difficult to
distinguish those meteors traveling east or west. At 29 and 27 km/sec., the
average Taurid meteor travels slowly through the skies.

The Orionids (ORI) peak on Sunday morning October 21 with a radiant located at
06:20 (095) +16. This position lies in northeastern Orion, three degrees west of
the second magnitude star Alhena (Gamma Geminorum). The radiant rises
near 2300 LDT and is best placed on the meridian near 0500. The Orionids are
normally faint and difficult to view from urban locations. It is advised to find
a safe rural location to view this display at its best. To see the best rates be
sure to wait until the moon has set. Rates peaked near 60 per hour last year and
are expected to be better than normal again this year. The Orionids have a
“plateau-like” peak therefore rates are still good on the mornings before and
after the expected maximum. At 66km/sec., the average Orionid meteor is swift.

Sirko Molau’s studies of video radiants has revealed activity in Monoceros
between October 17 and 26, peaking on the 24th. The position at maximum activity
is 6:56 (104) +11. This position lies in northeastern Monoceros, three degrees
southeast of the third magnitude star Xi Geminorum. Visual activity is expected
to be low, but detectable. This radiant is very close to the Orionid radiant therefore
distinguishing these meteors from the Orionids will be difficult at best. The
radiant is best placed near 0600 local daylight time. At 59km/sec., the average
Xi Geminid will appear as swift.

The Epsilon Geminids (EGE) are active from a radiant located at 07:00
(105) +27. This position lies in central Gemini, four degrees northeast of the
third magnitude star Epsilon Geminorum. Maximum activity occurred on
October 18 with an expected ZHR of two. Current rates will be most likely be near
one per hour. Recent studies of video data by Sirko Molau has indicated that this
shower is more active earlier in the month with a maximum occurring on October 14.
Weaker rates occurring now would indicate the earlier maximum is correct. At
70km/sec., the average Epsilon Geminid is swift. Be careful not to confuse these
meteors with the far more numerous Orionids. Including both radiants within
your field of view would help prevent this problem.

The Leo Minorids (LMI) are active for only one week centered on October 24.
ZHR’s are usually low but the radiant is far removed from the Orionids and
Epsilon Geminids so that any possible shower members should be easily
identified. This radiant is currently located at 10:56 (164) +37, which
places it on the Leo Minor/Ursa major border, four degrees north of the fourth
magnitude star 46 Leo Minoris. The radiant is best placed just before dawn
when it lies highest in a dark sky. This shower is better situated for
observers situated in the northern hemisphere where the radiant rises far
higher into the sky before the start of morning twilight. At 62km/sec., the
average Leo Minorid is swift.

Sporadic rates have reached maximum for observers in the northern
hemisphere and are now slowly rising for those located south of the equator. One
would expect to see approximately sixteen random meteors during the last hour before
dawn from rural observing sites in the mid-northern hemisphere (45 N). During the
first dark hour after the end of evening twilight, perhaps three random meteors can
be seen per hour. As seen from the mid-southern hemisphere (45 S) late morning rates
would now be near five per hour. During the first dark hour after the end of evening
twilight, perhaps one random meteor can be seen per hour. Moonlight interferes with
evening rates.