Results of the IMO Video Meteor Network - September 2008
========================================================
The weather was mediocre in September 2008. Many cameras got just a few
longer cloud gaps or had to pause completely inbetween. Only around
September 10 and 25 there were longer spells of clear sky at most sites.
Once more, Carl Hergenrother was the exception: He enjoyed perfect weather
all month long at Tucson and missed just a single night.
The monthly total of more than 2000 hours of effective observing time
and almost 9000 meteors was only thanks to the fact, that more than half
of all cameras are automated by now and therefor run without interruption.
With respect to the observing time, the last month was slightly behind the
best September 2006, and with respect to the meteor number it was slightly
ahead.
There are no major meteor showers is September. However, that does not mean
that there is nothing interesting to be observed. This time, the analysis
was centered around the minor shower of the September Perseids (SPE).
According to the IMO handbook, this shower is active between September 5
and 17 and reaches a peak ZHR of roughly 5 near September 9. The shower
was confirmed by the first complete meteor shower analysis two years ago,
but the radiant position derived from the video data differed by more than
10 degrees from the expected position.
This year Enrico Stomeo informed me, that his camera MIN38 had recorded seven
meteors on September 8/9, which seemed to originate from a radiant at
alpha=48°, delta=38° (figure 1). That radiant fits much better to the
epsilon-Perseids of Peter Jenniskens' list (alpha=50°, delta=39°) than to
the September Perseids of IMO (alpha=60°, delta=47°). So it was a good
occasion to examine this shower in more detail.
Figure 1: The radiant plot of MIN38 from September 8/9, 2008, shows a radiant
away from the position expected for the September Perseids.
The second analyses of the IMO Video Meteor Database presented this year
yielded a shower with an activity interval between September 3 and 14
consisting of 760 shower members. Figure 2 shows the radiant positions that
were derived. Between September 6 and 13 (dark red) the radiant is
well-defined. The drift is uniform and fits well to the radiant drift
expected for SPE. However, the offset in the radiant position by more than
10 degrees compared to the IMO handbook was confirmed. On September 8/9,
it is located at alpha=47°, delta=39°, which fits well to the figures
given by Enrico and to the epsilon-Perseids of Jenniskens. The velocity was
determined to 65 km/s which is in good agreement to the IMO handbook (64 km/s)
and Jenniskens' list (64.5 km/s).
Figure 2: Radiant position of the September Perseids derived from the IMO
Video Meteor Database.
Due to the similarity of both showers there is certain evidence, that the
September Perseids of IMO are identical to the epsilon-Perseids of Jenniskens,
whereby the radiant position in the IMO working list is erroneous.
A glimpse at the activity profile of the September Perseids (figure 3,
red bars) shows a weak maximum between September 9 and 11. That fits well
to the long-term activity profile of IMO (blue dots). Only the short-term
peak at September 9 is not visible. However, as the interval length of the
video data analysis is two degrees, there is a chance that a short peak is
smeared out. In addition we should remember that the visual activity profile
is based on a radiant that differs more than 10 degrees from the true
position.
Figure 3: Activity profile of the September Perseids. The blue dots represent
the ZHR curve from the current IMO handbook.
And what about 2008? Different American observers reported enhanced activity
in the morning hours of September 9. Two all-sky cameras recorded more than
20 bright meteors and fireballs up to -8 mag. The enhanced rates lasted
between 6 and 10 UT. This was confirmed by a visual observer, who observed
many shower members between 7 and 9 UT. His highest count was 12 September
Perseids between 8 and 8:30 UT.
What do our video data show? Unfortunately, the most interesting time
interval was outside the European night time hours, when most cameras were
active. Still, the data of 13 cameras from the European night of
September 8/9 were analysed first. In the beginning, the meteor shower
assignment was recomputed with the corrected radiant position. Then, the
hourly September Perseid count was determined for each camera separately,
the counts were corrected by the radiant altitude, and finally averaged
over all cameras. In parallel, the hourly sporadic count was determined.
Figure 4 shows the resulting 2008 activity profile based on 68 SPE and 427 SPO.
The radiant altitude corrected activity profile of the September Perseids
was almost constant in the course of the nights, whereas the sporadic
activity increased towards the morning as expected. Overall the SPE count
was 15% of the SPO count, which fits well to the long-term value from the
IMO database (13%). That is, the activity was not unusual as confirmed by
visual observers in Europe.
Figure 4: Activity profile of the September Perseids from video observations
on September 8/9, 2008.
The two American cameras SALSA and BOCAM enjoyed clear skies, too, even
though they recorded less meteors because of lower camera sensitivity and
a brighter observing site, respectively. Between 7 and 12 UT both cameras
recorded an overall of 13 SPE and 38 SPO. The increase in the fraction of
September Perseids is obvious. Half of the SPE recorded by SALSA were
captured between 8 and 9 UT, whereas the shower meteors were equally
distributed in the data set of BOCAM. If the data from both cameras are
averaged, we find rates that were enhanced by a factor of four to five
compared to the hours before. This leads to an peak ZHR estimate of
10 to 20, which is of the same order of magnitude as the visual results.
From the all-sky recordings alone one might have expected an even higher
ZHR, but the population index was obviously very small. As the number of
meteors increased only slightly towards the fainter meteors, the all-sky
cameras were able to record a significant fraction of the shower meteors
even with their low limiting magnitude. That pretended higher activity.
1. Observers
============
Code Name Place Camera FOV LM Nights Time Meteors
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BRIBE Brinkmann Herne HERMINE (0.8/6) 55 dg 3 mag 24 120.9 h 431
CASFL Castellani Monte Baldo BMH2 (0.8/6) 55 dg 3 mag 15 74.6 h 181
CRIST Crivello Valbrevenna STG38 (0.8/3.8) 80 dg 3 mag 11 60.8 h 401
ELTMA Eltri Venezia MET38 (0.8/3.8) 80 dg 3 mag 2 16.4 h 62
GONRU Goncalves Tomar TEMPLAR1 (0.8/6) 55 dg 3 mag 24 181.9 h 955
HERCA Hergenroth. Tucson SALSA (1.2/4) 80 dg 3 mag 29 223.6 h 460
HINWO Hinz Brannenburg AKM2 (0.85/25) 32 dg 6 mag 10 47.3 h 197
KACJA Kac Kostanjevec METKA (0.8/8) 42 dg 4 mag 10 57.2 h 137
Kamnik REZIKA (0.8/6) 55 dg 3 mag 6 41.6 h 269
Ljubljana ORION1 (0.8/8) 42 dg 4 mag 18 67.1 h 143
KOSDE Koschny Noordwijkerh. TEC1 (1.4/12) 30 dg 4 mag 5 19.9 h 45
LUNRO Lunsford Chula Vista BOCAM (1.4/50) 60 dg 6 mag 22 125.8 h 779
MOLSI Molau Seysdorf AVIS2 (1.4/50) 60 dg 6 mag 9 58.2 h 1036
MINCAM1 (0.8/6) 55 dg 3 mag 21 82.5 h 221
Ketzuer REMO1 (0.8/3.8) 80 dg 3 mag 21 111.4 h 448
REMO2 (0.8/3.8) 80 dg 3 mag 19 114.7 h 382
PRZDA Przewozny Berlin ARMEFA (0.8/6) 55 dg 3 mag 14 90.9 h 376
SLAST Slavec Ljubljana KAYAK1 (1.8/28) 50 dg 4 mag 14 62.7 h 131
STOEN Stomeo Scorze MIN38 (0.8/3.8) 80 dg 3 mag 8 35.5 h 116
STORO Stork Kunzak KUN1 (1.4/50) 55 dg 6 mag 2 5.4 h 155
Ondrejov OND1 (1.4/50) 55 dg 6 mag 3 22.7 h 489
STRJO Strunk Herford MINCAM2 (0.8/6) 55 dg 3 mag 23 92.5 h 279
MINCAM3 (0.8/8) 42 dg 4 mag 17 85.4 h 249
MINCAM5 (0.8/6) 55 dg 3 mag 17 99.8 h 404
WEBMI Weber Chouzava TOMIL (1.4/50) 50 dg 6 mag 2 4.4 h 178
YRJIL Yrjola Kuusankoski FINEXCAM (0.8/6) 55 dg 3 mag 17 104.1 h 372
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Overall 30 2007.3 h 8896
2. Observing Times (h)
======================
Sep 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
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BRIBE 4.4 4.0 4.8 4.2 0.3 5.5 - 6.3 1.7 6.6 3.8 - 6.2 2.9 0.7
CASFL 3.4 1.3 4.9 1.0 4.3 3.5 9.2 8.5 6.3 4.9 1.9 - - - -
CRIST - - - - - - - - - - - - - 5.0 6.4
ELTMA - - - - - - - 9.2 7.2 - - - - - -
GONRU 8.2 7.8 - - - - 9.5 8.2 8.8 6.4 9.4 9.3 9.0 9.7 8.5
HERCA - 7.6 9.5 9.0 9.7 9.1 9.7 7.1 9.4 7.4 1.8 1.3 9.3 9.9 6.9
HINWO - 0.5 0.6 - 0.6 - - 8.8 8.8 3.1 3.9 - - - -
KACJA 6.1 - 5.2 - 5.5 6.8 2.2 6.5 6.7 4.6 4.2 - - - -
- - - - - - - - 6.9 7.3 5.4 - - - 3.5
3.0 3.3 1.2 1.7 1.6 7.1 2.5 6.2 7.9 7.4 5.4 - - - -
KOSDE - - - - - - - - 0.7 - - - 7.1 4.3 -
LUNRO - 9.0 5.2 9.3 9.2 5.2 - - 6.6 1.8 3.6 1.0 - 6.0 2.9
MOLSI 4.7 8.2 - - 3.7 - - 8.5 5.4 - - - - - -
1.9 4.9 - 0.4 4.1 - 0.3 9.3 6.4 3.9 1.9 - 2.5 - -
4.5 5.0 3.6 6.7 - - 1.9 9.0 9.1 9.1 9.2 8.8 4.7 0.7 0.2
5.5 4.0 - 6.1 - - 3.4 7.5 8.0 9.0 9.1 8.8 3.5 - 0.7
PRZDA 5.5 6.0 2.7 5.3 - - 4.9 8.5 8.6 5.7 5.4 6.3 - - -
SLAST 3.7 1.3 3.8 2.3 4.7 4.4 - 4.8 9.0 5.3 3.5 - - - -
STOEN - - - - - - - 8.8 6.4 1.6 - - - - -
STORO - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - -
STRJO 5.3 2.0 4.5 2.0 - 1.4 2.5 4.4 2.0 5.5 1.0 1.4 5.3 - 1.0
4.2 - 7.9 1.2 - - - 2.4 1.0 4.0 - - 7.7 - 4.9
7.9 - 5.0 2.0 - - - 4.5 1.7 5.5 - - 8.0 - 1.9
WEBMI - - - - - - - - - - - - - - -
YRJIL - - 1.2 5.2 2.4 - 5.3 - - 5.4 5.8 - 8.0 - -
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Sum 68.3 64.9 60.1 56.4 46.1 43.0 51.4128.5128.6104.5 75.3 36.9 71.3 38.5 37.6
Sep 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
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BRIBE - 5.7 - 10.4 3.3 6.6 1.4 - 9.2 9.3 9.9 8.9 0.8 4.0 -
CASFL - - - - 2.5 - 6.1 - - - - - 10.4 6.4 -
CRIST 9.1 1.2 - - - - 6.6 - 7.4 4.2 1.0 9.5 9.4 1.0 -
ELTMA - - - - - - - - - - - - - - -
GONRU 6.9 1.2 9.4 7.1 1.7 - - 4.2 10.1 9.7 9.6 9.1 1.3 7.2 9.6
HERCA 10.0 1.3 7.1 9.6 6.7 6.7 7.7 8.2 10.2 10.3 4.2 9.1 10.4 10.5 3.9
HINWO - - - - - - - 1.2 - - - 9.8 10.0 - -
KACJA - - - - - - - - - - - - - 9.4 -
- - - - - - - - - 10.1 8.4 - - - -
4.8 0.7 0.5 4.8 2.5 - - 0.5 1.9 - - - 2.3 1.8 -
KOSDE - 2.4 - - - - - - - - - 5.4 - - -
LUNRO - - 0.5 3.5 7.5 - 4.3 3.0 9.8 10.1 7.1 - 1.0 9.0 10.2
MOLSI - - - - - - - 4.9 - - 5.1 9.6 8.1 - -
- 5.4 5.9 3.0 1.0 2.1 - 0.4 - 1.6 5.4 10.5 10.5 1.1 -
- 0.2 3.5 - - - - - 6.6 9.2 10.2 7.8 0.4 1.0 -
- - 5.1 - - 1.9 - - 10.1 8.2 10.2 9.3 2.9 1.4 -
PRZDA - - - - - - - - 6.2 10.2 10.2 5.4 - - -
SLAST - - - - - - - 0.5 3.2 - - - 9.8 6.4 -
STOEN - - - 0.6 - - 2.9 5.9 - - - 2.3 - 7.0 -
STORO - - - - - - - - 0.9 - 4.5 - - - -
- - - - - - - - - - 4.5 8.8 9.4 - -
STRJO - 4.3 6.0 2.2 1.7 4.7 - - 6.8 7.2 9.8 8.8 - 2.7 -
- 7.9 9.2 2.3 1.5 5.0 - - 3.9 6.6 7.1 8.6 - - -
- 6.4 8.0 4.9 3.5 5.7 - - 6.1 9.1 9.8 9.8 - - -
WEBMI - - - - - - - - - - - 2.0 2.4 - -
YRJIL - - - - 8.7 4.2 9.2 5.3 9.4 3.7 6.7 - 7.6 8.6 7.4
--------------------------------------------------------------------------------
Sum 30.8 36.7 55.2 48.4 40.6 36.9 38.2 34.1101.8109.5123.7134.7 96.7 77.5 31.1
3. Results (Meteors)
====================
Sep 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
--------------------------------------------------------------------------------
BRIBE 13 20 17 13 1 24 - 25 8 34 11 - 30 6 6
CASFL 8 3 20 3 6 12 23 22 12 10 5 - - - -
CRIST - - - - - - - - - - - - - 39 33
ELTMA - - - - - - - 47 15 - - - - - -
GONRU 44 31 - - - - 50 41 50 20 76 49 55 52 36
HERCA - 20 26 20 20 21 21 16 25 17 7 3 19 13 10
HINWO - 1 1 - 1 - - 43 22 15 20 - - - -
KACJA 9 - 8 - 11 21 2 18 19 21 10 - - - -
- - - - - - - - 46 49 20 - - - 27
6 6 3 3 3 13 4 12 26 18 9 - - - -
KOSDE - - - - - - - - 2 - - - 14 13 -
LUNRO - 56 44 51 59 99 - - 42 3 7 2 - 23 6
MOLSI 74 92 - - 61 - - 194 71 - - - - - -
5 11 - 1 10 - 1 37 13 9 6 - 7 - -
23 11 18 23 - - 6 39 34 30 34 47 18 3 1
28 14 - 26 - - 6 24 29 32 29 40 20 - 3
PRZDA 12 28 12 19 - - 31 29 30 30 25 34 - - -
SLAST 5 2 6 4 8 9 - 6 26 12 9 - - - -
STOEN - - - - - - - 46 15 2 - - - - -
STORO - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - -
STRJO 12 11 19 8 - 3 1 15 9 19 3 4 15 - 3
13 - 20 4 - - - 11 2 8 - - 25 - 14
27 - 26 8 - - - 24 4 20 - - 27 - 5
WEBMI - - - - - - - - - - - - - - -
YRJIL - - 1 19 7 - 16 - - 22 19 - 37 - -
-------------------------------------------------------------------------------
Sum 279 306 221 202 187 202 161 649 500 371 290 179 267 149 144
Sep 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
--------------------------------------------------------------------------------
BRIBE - 14 - 22 12 24 4 - 24 38 25 39 5 16 -
CASFL - - - - 6 - 17 - - - - - 17 17 -
CRIST 62 5 - - - - 51 - 78 16 7 47 60 3 -
ELTMA - - - - - - - - - - - - - - -
GONRU 31 2 34 24 2 - - 17 43 68 64 73 6 45 42
HERCA 22 5 12 16 12 16 15 11 21 20 8 12 23 24 5
HINWO - - - - - - - 3 - - - 46 45 - -
KACJA - - - - - - - - - - - - - 18 -
- - - - - - - - - 77 50 - - - -
10 1 1 9 5 - - 1 4 - - - 6 3 -
KOSDE - 5 - - - - - - - - - 11 - - -
LUNRO - - 2 6 27 - 10 7 39 40 154 - 5 30 67
MOLSI - - - - - - - 33 - - 163 172 176 - -
- 13 24 10 5 3 - 2 - 4 18 18 19 5 -
- 1 20 - - - - - 27 25 50 34 1 3 -
- - 15 - - 5 - - 33 25 28 18 4 3 -
PRZDA - - - - - - - - 22 41 32 31 - - -
SLAST - - - - - - - 2 5 - - - 23 14 -
STOEN - - - 2 - - 6 28 - - - 5 - 12 -
STORO - - - - - - - - 14 - 141 - - - -
- - - - - - - - - - 91 203 195 - -
STRJO - 9 13 5 5 15 - - 26 27 27 22 - 8 -
- 23 30 10 3 22 - - 9 19 16 20 - - -
- 24 31 12 8 30 - - 47 37 38 36 - - -
WEBMI - - - - - - - - - - - 74 104 - -
YRJIL - - - - 36 7 42 8 34 10 16 - 27 49 22
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Sum 125 102 182 116 121 122 145 112 426 447 928 861 716 250 136
Sirko Molau, 2008/10/29