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
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...
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.
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.
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.
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.
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.
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.
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NAMN email: namn@namnmeteors.org
NAMN website: http://www.namnmeteors.org
Mark Davis, meteors@comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network
Wayne T. Hally, meteoreye@comcast.net
High Bridge, New Jersey, USA
Writer, NAMN Notes
Lew Gramer, dedalus@alum.mit.edu
Homestead, Florida, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'
Kevin Kilkenny,
namnfireball@earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites
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