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
--------------------------------------------------------------------------------
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
--------------------------------------------------------------------------------
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
--------------------------------------------------------------------------------
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   -    -
--------------------------------------------------------------------------------
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
--------------------------------------------------------------------------------
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
-------------------------------------------------------------------------------
Sum   125  102  182  116  121  122  145  112  426  447  928  861  716  250  136

Sirko Molau, 2008/10/29