(meteorobs) NAMN Notes: November 2007

Mark Davis meteors at comcast.net
Wed Oct 31 20:55:57 EDT 2007


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NAMN Notes: November 2007
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NAMN Notes is a monthly newsletter produced by the North American Meteor
Network and is available both via email and on the NAMN website at:

http://www.namnmeteors.org


Contents:
1. Orionids Come Back Strong in 2007...
2. Orionids and Taurids Continue in November...
3. Discrimination of Close Radiants...
4. A Good Year for Watching Leonids, but...
5. Other November Activity...
6. For More info...


1. Orionids Come Back Strong in 2007...

It was suggested this year's Orionids might match last year's exceptional
activity, and that appears to be the case. As of the date of this issue,
there have been 1597 Orionids reported to the NAMN in just over 126 hours of
observing time (Teff). That's an average for the whole "moonth" between Full
Moons of 12.7 per hour. This included a considerable amount of off peak
activity.

The vast majority of the Orionids were counted during the 4 day peak
period from the 20-23 of October. For that time frame, 1515 Orionids
appeared in 65.31 hours, an average of over 23 per hour. That's mighty
impressive, since due to location and moonlight, many observations took
place with only fair limiting magnitudes, and the long term average ZHR is
only 23 using an LM of +6.5!

The International Meteor Organization's (IMO) on-the-fly Orionid graph
(which is also raw data, with no Quality Control yet applied) shows peak
ZHR's of 78 +/-4 and 77 +/-6 at 00:44 and 08:21 UT on the 22nd respectively.
It can be viewed here:

http://www.imo.net/live/orionids2007/

The information will probably be updated if you visit now, but it does
verify that this was indeed a much above normal year. Based on reports
received so far by both organizations, it appears that the Orionids were
once again brighter than usual, supporting the Jupiter resonance effects,
and the old age of the meteoroids (referred to last month) that we sampled
on our path through the Halley's Comet stream.

Such enhanced activity might continue for the next year or two, although
next year will be much more challenging to watch due to a half lit moon very
near the radiant. Also reported were 74 epsilon-Geminids (EGE), and 127
Taurids.


2. Orionids and Taurids Continue in November...

The Orionids continue through November 7th according to the IMO's
working list of meteor showers, although Sirko Molau's summary of video
observations suggests that the activity continues through the 11th, so it
might be worth watching them for a few extra days. The radiant actually lies
in Gemini this month, so be sure to check the IMO's 2007 shower calendar at
http://www.imo.net/calendar/2007  for the correct location. The moon doesn't
rise until the early morning hours, so there should be some dark sky time to
monitor activity from this shower.

The Southern and Northern Taurids reach their peak levels during the
first two weeks of November. The IMO lists the STA peak on the 5th and the
NTA peak on the 12th. In truth, the actual peak varies from year to year,
and can occur in any individual season from late October through mid
November. The radiants (please see section #3 below for suggestions on how
to improve the amount of precise data we can collect) actually finally move
into the constellation of Taurus on November 4th. See the IMO calendar above
for daily locations. After the Full Moon on the 24th, the Taurids will have
ended and we go back to reporting ANT (Antihelion) for the ecliptic activity
as the radiant moves from Taurus into Gemini.


3. Discrimination of Close Radiants...

I have noted that many observers report the Taurids as a combined radiant
(TAU) rather than separating the Northern and Southern Taurids. I thought
I'd offer a suggestion to help make it easier to discriminate whether an
individual meteor belongs to the northern or southern branch. This is a
method that I was exposed to very early on from the NAMN, and I highly
recommend it. It involves the use of an alignment cord or string.

Although originally proposed to help with meteor plotting rather than
counting, I find it is an invaluable way to help with recording accurate
data this time of year. It makes it pretty easy to select the proper Taurid
radiant for a meteor, and also is a big help during October when assigning
EGEs, ORIs and the new radiant (at least temporarily called the xi-Geminids;
XGE) from Mr. Molau's video summary. These three radiants are stacked one
above the other in a space of only 15 degrees, so it requires a bit of
effort to perform accurate shower association.

The basic concept is to have a cord of some kind easily accessible so that
when you see a meteor across the sky, you can immediately place an alignment
device over the path so you can backtrack to the radiant location. I keep 2
different kinds in my meteor kit, both dark and light colored so I can use
whichever gives the best contrast against the sky. I also keep a spare of
each in the kit for when I inevitably lose one during a long observing
session. That used to be much more of a problem, but over the last year or
so I have started making a thumb sized loop on each end, so I just "attach"
it to my left thumb, making it much harder to misplace. It's not impossible,
hence the spares in the kit. Oh and I also have two more spares in the car.
Better to have too many than not enough! That goes for anything involved in
meteor observing. It takes only a second for the brain to realize I've seen
a meteor, and by now the action to align the cord with the path is almost a
reflex. Then I can see where that path intersects either the radiants in
Orion and Gemini, or the Taurid radiants in a few seconds.

A question in the back there? "Yes, Wayne, why is that important?" Another
good question, I love this crowd. In October, with 3 radiants in Orion and
Gemini close together, and through November with the two Taurid radiants so
close to each other, a lot of detail is lost. Many beginning meteor watchers
count anything near Orion as Orionids, thereby lumping in the other two
showers in the count. Since they are both very low rate showers, and the
Orionids are so overwhelming, statistically it's not a big deal for the
ORIs. But a lot of data is lost on the EGEs. And as far as the Northern and
Southern Taurids are concerned, one reason the peak is described so loosely
in section #2 above is precisely because so many reports list only Taurids.
The radiants are only 6 or 7 degrees apart, so it isn't easy to properly
assign the shower members. But once you get used to it, you will find the
process effortless and can improve the quality and value of your efforts in
counting meteors.

I have added an improvement for when I am plotting meteors - I have placed
knots in the cord 10 degrees apart (when my arms are fully extended) to aid
in estimating meteor velocities. I haven't had a chance to try this much,
since during October I mostly count, not plot, meteors. For those that have
advanced to plotting meteors, it might be worth a try. I'll let you all know
how it works out once I have some plotting time out under the sky.


4. A Good Year for Watching Leonids, but...

The moon is our friend this month for watching the Leonids. Whether the
shower will give us much to see remains to be seen. The nodal crossing,
which is the theoretical "annual" peak, is at 2:50 UT on November 18th. The
only enhancement I've been able to find so far is that of Mikhail Maslov and
Dr. Peter Jenniskens, who propose a short peak of ZHRs near 60/Hour at 23:05
UT (Nov 18), which will be during daylight in North America. It will be
visible from Asia, Indonesia and surrounding areas. The nodal crossing
should give us only normal rates of background Leonids ~ 15 an hour, and
even that is not visible from North America, since it occurs before the
radiant has risen. The best locations for that should be in Europe, the
Middle East, and Northern Africa. After what we've seen over the last
decade, it will be a bit of a letdown to see Leonid rates fall back to their
normal levels. It's easy to get spoiled. The moon will be setting near
midnight, leaving the morning hours with dark skies, and highest rate should
occur during the early morning hours of the 18th and 19th. The next
outburst, from Dr. Jenniskens' book "Meteor Showers and their Parent Comets"
is expected in 2009.

These months, from October 30th through November 3rd, there are
evening moon free hours. Daylight savings time ends on the morning of the
4th for the U.S., so from then until the 16th, it's moon free for most of
the night, with at least 8 dark sky hours. For the Leonid peak, the moon
sets
around midnight, as the radiant rises in the eastern sky. From the 16th to
the 22nd there is early morning dark sky time. Full Moon is on the 24th, and
the evening hour "moonth" opens again on November 27th or 28th, depending on
your location.

The Leonids are active from November 10-23 according to the current
IMO working list, although once again, video data suggests a longer period
from the 8th through the 28th. The Leonids are the fastest shower meteors
we see, with a velocity of 71 km/sec when they intersect the atmosphere.


5. Other November Activity...

There are two showers of interest in Monoceros toward the end of the month.
The first is a periodic shower, the alpha-Monocerotids (AMO). This shower
usually has a ZHR around 5 per hour, peaking this year at 03:10 UT on
November 22nd, with activity lasting from the 15th to the 25th. However,
this shower has produced some very short intense outbursts with ZHRs
exceeding 400 for a few minutes. If you are out observing on the morning of
the 22nd, keep your breaks very short, or you could miss the whole thing!!
The radiant is just below Procyon, and the velocity is fast, comparable to
the Orionids (65 km/sec).

The other shower is the Monocerotids, active from 27th (IMO) or possibly as
early as the 17th (Sirko Molau) through December 19th. The peak, with a weak
ZHR of only 2 is around December 9th. This month, the radiant is between the
top of Orion and the lower left corner of LM counting area #8 (zeta Tauri).
These are medium fast meteors, at 42 km/sec.

Here are the magnitudes of some objects you might run into overnight:

Venus, (Magnitude -4.3) rising in Virgo very close to morning twilight.
Jupiter, (Magnitude -1.8) setting in Ophiuchus during evening twilight.
Sirius, (Magnitude -1.4) below Orion.
Mars, (Magnitude -0.8) in Gemini rising before midnight.
Capella, (Magnitude +0.1) rising before Mars.
Procyon, (Magnitude +0.4) below Orion
Saturn, (Magnitude +0.8) in Leo, rising in the east toward dawn.

The 3 stars in Orion's belt are (Magnitude +1.6, +1.7, and +2.1).

Epsilon Gemini (Magnitude +3.1) the corner of LM area #4.
Sigma and rho Gem, the stars just above Castor and Pollux are
(Magnitude +4.1 and +4.2); neither should be included when counting LM area
#4.


6. For More Info...

Once again, I'd appreciate any thoughts you have on NAMN notes. My style is
a bit different than Cathy Hall's so if something is missing that you liked,
or if there's something else you'd like to see, please contact me at the
email address below.

NAMN email: namn at namnmeteors.org
NAMN website: http://www.namnmeteors.org

Mark Davis, meteors at comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

Wayne T Hally, meteoreye at comcast.net
High Bridge NJ
Writer, NAMN Notes

Lew Gramer, dedalus at alum.mit.edu
Homestead, Florida, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'

Kevin Kilkenny, namnfireball at earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites

Back issues of NAMN Notes can be found online at the NAMN website and in
the MeteorObs archives at:
http://www.meteorobs.org by selecting 'Browse Archive by Month'

To subscribe to the meteor email list:
Contact Lew Gramer at: dedalus at alum.mit.edu

==============================================
Here's to 'Clear Skies' for November...

November 2007 NAMN Notes
Written by Wayne T Hally & edited by Mark Davis
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