Results of the IMO Video Meteor Network - April 2008
====================================================

With nearly 1500 hours of effective observing time and more than 3000 meteors, 
April 2008 could not keep up with the record-breaking April before. However, 
there were major differences between the individual observing sites. Once 
more, Carl Hergenrother was on top of the list - he missed only a single 
night at his Arizona observing site. Observers in northern and western 
Germany managed to collect twenty and more observing nights as well, but 
farther south the weather was only mediocre.

"Highlight" of the month with respect to meteors were once more the Lyrids. 
Their maximum, however, coincided with full moon, so that no spectacular 
display was to be expected. This is also reflected by the meteor number, which 
was only slightly higher on April 22 than on other nights. Overall, the 
activity remained low with an average of two meteor records per hours.

If nothing happens in the sky, then it is time to put some effort into the 
data analysis. Together with Pete Gural, I analyzed the sporadic meteors in 
the IMO Video Meteor Database with its nearly 330,000 records. The results 
were presented a few days ago at the "Meteoroid and Meteor Observations as a 
Basis for Models" conference in Huntsville, Alabama. Here I would like to 
present a few facts and figures from our presentation.
 
During the analysis, meteors were first assigned to the known meteor showers 
(based on the IMO Working List). For the remaining meteors it was checked, 
whether they belong to one of the six known sporadic sources (Helion, 
Antihelion, N/S Apex , N/S Toroidal - the base data of which were taken from 
the work of Margaret Campbell-Brown), or whether they were "true" sporadics. 
In the end it turned out, that about one quarter of all meteors are shower 
meteors (most of all Perseids, Orionids and Geminds). Another 15% could be 
assigned to the sporadic sources, and more than half of all meteors (60%) are 
true sporadics. Among the sporadic sources, about half of the meteors belong 
to the Antihelion source, and about one quarter to the N Apex source. The 
remaining meteors are S Apex and N Toroidal meteors in equal frequency 
(Figure 1, left). The strength of the northern sporadic branches can be 
explained easily when considering that 95% of all meteors in the database 
were recorded in the northern hemisphere. When the meteor frequencies are 
corrected for the observing geometry it turnes out, that the northern and 
southern branch of the Apex and Toroidal source are about equaly strong.


Figure 1: Relative frequency of the individual sporadic sources in the 
IMO Video Meteor Database (left  uncorrected; right  corrected for 
observing geometry)

Looking at the annual distribution of meteors (normalized to the overall 
number of sporadic meteors in that particular solar longitude interval) we 
see some variation in the activity profile of the N Apex source. Once more, 
if the observing geometry (i.e. the observability of a particular source in 
the course of the year) is accounted for, all sources show at the first 
approximation a roughly constant activity, and also the percentage of the 
sporadic sources among all sporadics varies only little.

It is more tricky to get an estimate of the absolute sporadic activity in 
the course of the year, as the particular observing conditions of each 
observation (limiting magnitude, size of field of view) are unknown. The 
effective observing time per night is also not part of the positional 
database PosDat. So we normalized the number of sporadics with the overall 
effective observing time per month (in the hope that the observing conditions 
are about the same when averaged over many years) and obtained a roughly 
sinusoidal activity graph with a minimum of more than two sporadics per 
hour in mid-March and a maximum of more than four sporadics per hour in 
mid-September (Figure 2).


Figure 2: Annual variation of the average number of sporadic meteors 
per hour (red  original values; yellow  Sine fit)


1. Observers
============

Code    Name        Place           Camera         FOV    LM Nights Time Meteors
--------------------------------------------------------------------------------
BENOR Benitez-S.  Las Palmas    TIMES4 (1.4/50)   20 dg  3 mag  6   11.0 h    23
                                TIMES5 (0.95/50)  10 dg  3 mag  7    7.3 h    21
BRIBE Brinkmann   Herne         HERMINE (0.8/6)   55 dg  3 mag 24   76.0 h   167
CASFL Castellani  Monte Baldo   BMH1 (0.8/6)      55 dg  3 mag 13   62.7 h   107
                                BMH2 (0.8/6)      55 dg  3 mag  9   39.6 h    49
CRIST Crivello    Valbrevenna   STG38 (0.8/3.8)   80 dg  3 mag  3   14.6 h    29
GONRU Goncalves   Tomar         TEMPLAR1(0.8/3.8) 80 dg  3 mag  8   64.7 h    95
HERCA Hergenroth. Tucson        SALSA (1.2/4)     80 dg  3 mag 29  221.4 h   305
HINWO Hinz        Brannenburg   AKM2 (0.85/25)    32 dg  6 mag 12   66.4 h   140
KACJA Kac         Kostanjevec   METKA (0.8/8)     42 dg  4 mag 15   71.4 h   131
                  Kamnik        REZIKA (0.8/6)    55 dg  3 mag  7   36.2 h    35
                  Ljubljana     ORION1 (0.8/8)    42 dg  4 mag 19   72.6 h    99
KOSDE Koschny     Noordwijkerh. ICC4 (0.85/25)    25 dg  5 mag 10   46.3 h    76
LUNRO Lunsford    Chula Vista   BOCAM (1.4/50)    60 dg  6 mag 15   92.4 h   251
MOLSI Molau       Seysdorf      AVIS2 (1.4/50)    60 dg  6 mag  8   44.2 h   375
                                MINCAM1 (0.8/6)   55 dg  3 mag 15   48.4 h    74
                  Ketzuer       REMO1 (0.8/3.8)   80 dg  3 mag 20   72.7 h   160
                                REMO2 (0.8/3.8)   80 dg  3 mag 12   47.4 h   163
PRZDA Przewozny   Berlin        ARMEFA (0.8/6)    55 dg  3 mag  3   18.0 h    51
ROBBI Roberto     Verona        FIAMENE (0.8/3.8) 80 dg  3 mag 12   44.9 h    81
SLAST Slavec      Ljubljana     KAYAK1 (1.8/28)   50 dg  4 mag 13   49.8 h    77
STOEN Stomeo      Scorze        MIN38 (0.8/3.8)   80 dg  3 mag 10   58.9 h   120
STORO Stork       Kunzak        KUN1 (1.4/50)     55 dg  6 mag  1    8.3 h    25
                  Ondrejov      OND1 (1.4/50)     55 dg  6 mag  3    9.8 h    51
STRJO Strunk      Herford       MINCAM2 (0.8/6)   55 dg  3 mag 23   39.8 h    80
                                MINCAM3 (0.8/8)   42 dg  4 mag  9   20.5 h    50
                                MINCAM5 (0.8/6)   55 dg  3 mag  9   29.3 h    67
YRJIL Yrjola      Kuusankoski   FINEXCAM (0.8/6)  55 dg  3 mag 21   96.0 h   158
--------------------------------------------------------------------------------
Sum                                                            30 1470.6 h  3060


2. Observing Times (h)
======================

Apr    01   02   03   04   05   06   07   08   09   10   11   12   13   14   15
--------------------------------------------------------------------------------
BENOR   -    -    -    -    -    -   2.0  2.7  3.4   -    -    -    -    -    - 
        -    -    -    -    -    -   3.2  0.3  3.8   -    -    -    -    -    -
BRIBE  0.3   -    -    -    -   7.0  4.5  1.7  3.7  2.0  5.1  1.8  0.3  2.0  3.3
CASFL  0.5   -   9.3  6.2  3.1   -   2.0   -    -   1.0   -    -    -    -    - 
       3.4  6.3  6.9  4.2  5.1   -   6.5   -    -    -    -    -    -    -    -
CRIST   -    -    -    -   5.8   -    -    -    -    -    -    -    -    -    -
GONRU  9.7  9.6  9.6  9.5   -   1.5   -    -    -    -   8.4   -    -    -    -
HERCA  7.2  7.8  8.3  3.2  9.7  9.7  9.6  9.6  6.9  9.5  9.5  9.4  9.4   -    -
HINWO   -    -    -    -    -    -   8.4  0.9   -   0.9   -   2.5  8.0   -   9.3
KACJA  1.3  4.6   -    -   8.8  3.5   -    -    -    -    -    -    -    -    - 
       4.2   -   1.4  5.4  7.3   -    -   6.0   -   6.0   -    -    -    -    - 
       2.8   -   5.1  7.1  6.1   -   1.8   -    -    -    -    -   0.6  8.2  2.8
KOSDE   -   2.3   -    -    -    -    -   8.2  7.9   -   6.8  3.3   -    -    -
LUNRO  4.8  8.5   -    -    -    -    -    -    -   3.9   -   8.3  9.0  4.5   -
MOLSI   -    -    -    -    -    -   6.0   -    -    -    -    -   7.9   -    - 
        -    -    -   0.2  0.3   -   9.0   -    -   0.3   -    -   8.6   -   0.7
       1.0   -   0.9  2.3   -   6.2  1.6  5.5   -    -    -    -   0.7   -    - 
       0.5   -    -    -    -    -    -    -    -    -    -    -   1.5   -    -
PRZDA   -    -    -   6.7   -    -    -    -    -    -    -    -    -    -    -
ROBBI  2.5  5.2  7.5   -    -    -   5.0  3.1   -    -   1.8   -    -    -    -
SLAST  0.7   -    -   7.2  3.4   -    -    -    -    -    -    -   1.4  6.0  5.0
STOEN  1.2  8.2   -    -   9.0   -   7.0   -    -    -    -    -   5.5   -    -
STORO   -    -    -    -    -    -   8.3   -    -    -    -    -    -    -    - 
        -    -    -    -    -   0.8  7.7  1.3   -    -    -    -    -    -    -
STRJO  1.0   -    -   1.5  2.7  1.0  0.5   -   0.5   -   2.0  1.0   -   1.7  1.5
        -    -    -    -    -    -    -    -    -    -    -   1.0   -    -    - 
        -    -    -    -    -    -    -    -    -    -    -   4.0   -    -    -
YRJIL  7.5  6.6  6.3  7.1   -    -    -    -   1.4  6.2  0.7   -    -   5.7  1.0
--------------------------------------------------------------------------------
Sum   48.6 59.1 55.3 60.6 61.3 29.7 83.1 39.3 27.6 29.8 34.3 31.3 52.9 28.1 23.6
    
Apr    16   17   18   19   20   21   22   23   24   25   26   27   28   29   30
--------------------------------------------------------------------------------
BENOR   -    -    -    -    -   2.5   -    -    -    -    -   0.2  0.2   -    - 
        -    -    -    -    -    -    -    -    -    -    -    -    -    -    -
BRIBE  6.3  6.2  2.9   -   6.0  8.4  2.3   -   0.7  1.0  3.8  2.3  0.3  1.4  2.7
CASFL   -    -    -   6.4   -    -   8.1  4.1  8.0  6.3  1.9  5.8   -    -    - 
        -    -    -   0.7  0.5   -   6.0   -    -    -    -    -    -    -    -
CRIST   -    -    -   1.0   -    -    -    -    -   7.8   -    -    -    -    -
GONRU   -    -    -    -    -    -    -    -    -    -    -    -   8.3   -   8.1
HERCA  7.6  3.3  6.1  9.2  7.2  9.1  7.7  9.1  8.9  9.0  3.0  8.9  8.9  7.8  5.8
HINWO   -   3.3   -   7.0  5.5   -    -   2.3   -    -   4.2  7.1   -   7.0   -
KACJA   -   1.8   -   5.2   -   3.5  3.3  4.7  2.3  3.4  7.6  7.9  7.8   -   5.7
        -    -    -    -    -    -    -    -   5.9   -    -    -    -    -    - 
        -    -    -   6.4  1.2  3.3  1.2  5.0  3.2  2.9  5.2  7.1  2.0  0.6   -
KOSDE   -    -    -    -    -   2.6   -    -   5.0   -   1.5   -    -   2.3  6.4
LUNRO   -   2.0  8.7  1.0   -    -   5.9   -    -   8.2  8.1  7.9  4.2  7.4   -
MOLSI   -    -    -    -   3.4   -    -   5.9  2.3   -   7.0  4.9   -   6.8   - 
        -   2.4   -   3.2  5.2   -    -   1.0  0.6  2.8  3.8  2.7   -   7.6   - 
        -    -   2.6  2.1  4.0  5.5  7.4  7.4  2.8  7.3  7.1  4.1  1.0  0.4  2.8
        -    -    -    -   6.1  6.0  6.0  6.5  1.7  4.3  5.8  6.0   -   1.1  1.9
PRZDA   -    -    -    -    -    -    -   6.9  4.4   -    -    -    -    -    -
ROBBI   -    -    -    -    -    -   2.0  1.1  5.1  6.0   -   3.9   -    -   1.7
SLAST   -    -    -   2.1   -    -    -   4.7  3.1  3.2  5.1  6.5   -    -   1.4
STOEN   -    -    -   7.4  4.2   -    -    -   7.9   -   2.4  6.1   -    -    -
STORO   -    -    -    -    -    -    -    -    -    -    -    -    -    -    - 
        -    -    -    -    -    -    -    -    -    -    -    -    -    -    -
STRJO  2.1  0.5  0.9  0.5  4.5  4.7  1.0  1.1   -   1.0  1.3  1.5   -   5.0  2.3
       1.7   -   1.0   -   3.5   -   5.4  1.0   -    -   2.3  1.0   -   3.6   - 
       4.7   -   1.7   -   4.8   -   2.5  1.0   -    -   4.0  2.7   -   3.9   -
YRJIL  2.8   -   3.9  5.3  5.2  3.8  4.9  4.2  4.6  3.7  2.6   -    -   3.8  8.7
--------------------------------------------------------------------------------
Sum   25.2 19.5 27.8 57.5 61.3 49.4 63.7 66.0 66.5 66.9 76.7 86.6 32.7 58.7 47.5


3. Results (Meteors)
====================

Apr    01   02   03   04   05   06   07   08   09   10   11   12   13   14   15
--------------------------------------------------------------------------------
BENOR   -    -    -    -    -    -    4    5    6    -    -    -    -    -    -
        -    -    -    -    -    -   10    2    9    -    -    -    -    -    -
BRIBE   1    -    -    -    -   11   10    2    8    5   14    3    1    7    5
CASFL   1    -   16    9    7    -    2    -    -    2    -    -    -    -    - 
        3    7   12    3    4    -    7    -    -    -    -    -    -    -    -
CRIST   -    -    -    -   11    -    -    -    -    -    -    -    -    -    -
GONRU  17   11   13   12    -    1    -    -    -    -   11    -    -    -    -
HERCA  10    5   11    4   14   16    9    8    3   12   10   10    9    -    7
HINWO   -    -    -    -    -    -   19    2    -    7    -    5   26    -    -
KACJA   1   13    -    -   14    5    -    -    -    -    -    -    -    -    - 
        3    -    2    7    8    -    -    5    -    5    -    -    -    -    - 
        2    -    6   11    6    -    2    -    -    -    -    -    1   12    5
KOSDE   -    5    -    -    -    -    -    7   11    -   11    7    -    -    -
LUNRO   7   12    -    -    -    -    -    -    -   10    -   30   30   20    -
MOLSI   -    -    -    -    -    -   75    -    -    -    -    -   92    -    - 
        -    -    -    1    1    -    9    -    -    2    -    -   13    -    2 
        2    -    2    3    -    7    6    4    -    -    -    -    1    -    - 
        1    -    -    -    -    -    -    -    -    -    -    -    2    -    -
PRZDA   -    -    -   12    -    -    -    -    -    -    -    -    -    -    -
ROBBI   4    9   16    -    -    -    6    3    -    -    3    -    -    -    -
SLAST   1    -    -   15    5    -    -    -    -    -    -    -    1    8    5
STOEN   3   15    -    -   17    -    8    -    -    -    -    -    7    -    -
STORO   -    -    -    -    -    -   25    -    -    -    -    -    -    -    - 
        -    -    -    -    -    2   46    3    -    -    -    -    -    -    -
STRJO   2    -    -    3    5    2    1    -    1    -    4    2    -    2    4 
        -    -    -    -    -    -    -    -    -    -    -    2    -    -    - 
        -    -    -    -    -    -    -    -    -    -    -   10    -    -    -
YRJIL  11    4    5    7    -    -    -    -    1    7    1    -    -    7    2
-------------------------------------------------------------------------------
Sum    69   81   83   87   92   44  239   41   39   50   54   69  183   56   30
     
Apr    16   17   18   19   20   21   22   23   24   25   26   27   28   29   30
--------------------------------------------------------------------------------
BENOR   -    -    -    -    -    6    -    -    -    -    -    1    1    -    - 
        -    -    -    -    -    -    -    -    -    -    -    -    -    -    -
BRIBE   9   11    7    -   15   23    6    -    3    2   10    5    1    4    4
CASFL   -    -    -   16    -    -   16    4   12   12    3    7    -    -    - 
        -    -    -    1    1    -   11    -    -    -    -    -    -    -    -
CRIST   -    -    -    3    -    -    -    -    -   15    -    -    -    -    -
GONRU   -    -    -    -    -    -    -    -    -    -    -    -   15    -   15
HERCA  10    7    3   13   15   20   28   17   13   12    4    9   10   12    4
HINWO   -    3    -   13   10    -    -    6    -    -   12   18    -   19    -
KACJA   -    4    -    9    -   20    5    8    3    3   11   15    6    -   14 
        -    -    -    -    -    -    -    -    5    -    -    -    -    -    - 
        -    -    -   12    2    4    3   10    3    3    7    7    2    1    -
KOSDE   -    -    -    -    -    7    -    -    7    -    3    -    -    6   12
LUNRO   -    4   18    1    -    -   19    -    -   15   21   25   27   12    -
MOLSI   -    -    -    -   23    -    -   45   14    -   50   27    -   49    - 
        -    4    -    4   10    -    -    2    2    5    5    4    -   10    - 
        -    -    6    6   22   30   26   15    4    9    9    3    1    1    3 
        -    -    -    -   17   31   29   28    3   20   12   14    -    4    2
PRZDA   -    -    -    -    -    -    -   24   15    -    -    -    -    -    -
ROBBI   -    -    -    -    -    -    2    3   10   12    -   11    -    -    2
SLAST   -    -    -    4    -    -    -    7    4    6    6   14    -    -    1
STOEN   -    -    -   27   10    -    -    -   17    -    3   13    -    -    -
STORO   -    -    -    -    -    -    -    -    -    -    -    -    -    -    - 
        -    -    -    -    -    -    -    -    -    -    -    -    -    -    -
STRJO   3    1    2    1    9   14    3    2    -    2    2    3    -    7    5 
        4    -    2    -   10    -   12    2    -    -    5    2    -   11    - 
       10    -    4    -    9    -    6    2    -    -    7    7    -   12    -
YRJIL   1    -    8    9   15   14   26   11   11    7    3    -    -    6    2
-------------------------------------------------------------------------------
Sum    37   34   50  119  168  169  192  186  126  123  173  185   63  154   64

Sirko Molau, 2008/06/02