Results of the AKM Video Meteor Network - July 2002
===================================================
Usually one would expect that the summer month July is full of clear nights
and the number of meteor records is only limited by the short nothern
nights, but this year has teached us the opposite again. The weather
in Germany was quite poor for most of the month, which ruined not only
meteor observations but also the summer holidays of many central Europeans.
At least there were a few clear nights by the end of July that were used for
tests of new meteor cameras.
Two month ago we initiated a group purchase of video cameras with Sony's
ExView HAD chip from the manufacturer Mintron in Taiwan. The cameras arrived
here in mid-July (at about Euro 250 per camera, half the usual dealer price).
They contain the high resolution 1/2" Sony chip, i.e. the best sensor
currently available. The cameras do not only have a high quantum efficiency,
but also a very low readout noise. Contrary to cheaper systems the Mintron
cameras have a number of additional options that can be controled by five
buttons and on-screen menus. These options are of little use for meteor
observers, but make this camera the first choice for all kinds of astronomical
imaging. Of special interest is the option to integrate up to 128 video frames.
In this mode the camera is still producing a PAL video signal with 50 frames/s,
but 128 subsequent frames are identical until the next exposure is finished.
You easily reach amazing limiting magnitudes that way!
For first system tests I used two 25mm f/1.4 and f/0.85 c-mount lenses from
Fujinon, as well as a 12mm f/1.4 low budget c-mount lens from Computar.
Interestingly there was almost no difference in performance between the first
two lenses. The field of view was 14.5x11 deg at 25 mm focal length, and 29x22
deg at 12 mm. When I integrated 32 frames (i.e. 0.64 s exposure time, the
maximum possible at my sub-urban Aachen skies) the camera revealed it's full
power. Figure 1 shows in the upper row the exposures with the 25 mm lenses
(left f/1.4, right f/0.85) and below with the 12mm lens. The bright star down
left is Deneb, gamma Cygni in visible in the lower right. I did not determine
the limiting magnitude of the images, but it was well beyond the visual limiting
magnitude and that of my image-intensified camera. Too bad that this option is of
little use for meteor observers. The low-budget Computar lens showed significant
vignetting, which was much weaker in case of the f/1.4 Fujinon lens (both are
1/2" lenses). The 1" f/0.85 lens was fully free of vignetting.
For test purposes I operated the new camera in parallel with my image-
intensified camera AVIS with identical field centers. Two of the meteors
recorded by both cameras are shown in Figure 2. On the left the meteor was
recorded with AVIS and on the right with the Mintron camera and the 25mm f/0.85
lens. The Mintron camera was connected to my old computer which is not able to
handle the full 25 frames/s. For this reason there are short breaks in the meteor
trails. My first impression was that the limiting meteor magnitude is about the
same for both cameras in this configuration. The main difference is the field of
view. The diameter of AVIS' FOV is 41 deg, i.e. eight times as large as the field
of the Mintron camera with 14x11 deg. On the other hand the latter camera is more
robust, shows less image distortion and a much sharper image with higher dynamic
range (whereas airplanes look like large blobs in the image-intensified camera,
the indicator lights are well resolved in the Mintron camera images), a higher
spatial resolution (the mean position error for reference stars was about 0.5',
compared to 3.5' for AVIS), and it is significantly cheaper.
At the same time, Joerg Strunk carried out tests with his Mintron camera as
well. He used a 6mm f/0.8 c-mount lens monitoring a much larger field of view.
Between June 27 and 29 he managed to record an overall of 61 meteors in
15 hours effective observing time. The large field of view resulted in a
large number of bright meteors, many of which being shower meteors. All in
all a very promising start with the new cameras!
Back to the AKM network: Whereas clear skies were the exception in central
Europe, the situation was much better on the Canary islands. Orlando
Benitez-Sanchez managed for the third time in a row to collect approximately
20 observing nights. Down under in Australia Steve Quirk broke again all
records under clear southern Winter skies. He reported 25 observing nights
with 300 hours effective observing time (hence, the camera was 40% of all time
in operation - more is hardly possible) and almost a thousand meteors. Still
in the end there were two July nights without observations in the AKM network.
1. Observers
============
Code Name Place Camera FOV LM Nights Time Meteors
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BENOR Benitz-S. Maspalomas TIMES4 (1.4/50) 20 dg 4 mag 19 136.5 h 277
MOLSI Molau Aachen AVIS (2.0/35) 40 dg 5 mag 12 38.7 h 235
MINCAM1 (0.85/25) 13 dg 5 mag 1 4.5 h 12
NITMI Nitschke Dresden VK1 (0.75/50) 20 dg 8 mag 4 12.6 h 39
QUIST Quirk Mudgee SSO-WAT1 (0.85/25) 13 dg 5 mag 25 300.0 h 989
RENJU Rendtel Marquardt CARMEN (1.8/28) 32 dg 5 mag 5 21.3 h 92
SPEUL Sperberg Salzwedel AKM1 (0.85/25) 32 dg 6 mag 3 11.5 h 88
STRJO Strunk Leopoldshoehe AKM2 (0.85/25) 32 dg 6 mag 3 14.3 h 137
MINCAM2 (0.8/6) 55 dg 3 mag 3 14.6 h 61
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Sum 29 554.0 h 1930
2. Observing Times (h)
======================
July 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
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BENOR - - - 6.5 - 5.2 7.5 7.3 7.4 7.0 - 7.4 6.9 7.7 7.2
MOLSI - - - - - - 2.3 4.9 - 0.2 4.4 - - - 3.5
- - - - - - - - - - - - - - -
NITMI - - - - - - - 4.0 3.2 - 1.2 4.2 - - -
QUIST 12.5 12.8 - - - 12.0 11.9 12.4 12.5 12.4 12.4 12.3 12.4 9.5 10.7
RENJU - - - - - - - - 2.8 - - - - - -
SPEUL - - - - - - - - - - - - - - -
STRJO - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - -
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Sum 12.5 12.8 - 6.5 - 17.2 21.7 28.6 25.9 19.6 18.0 23.9 19.3 17.2 21.4
July 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
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BENOR 6.8 - 7.4 - 7.7 7.5 7.6 8.0 7.6 - 7.1 - 6.7 - - -
MOLSI - - 0.7 3.5 6.0 - 0.6 - - - - 4.2 2.6 5.8 - -
- - - - - - - - - - - - - 4.5 - -
NITMI - - - - - - - - - - - - - - - -
QUIST 12.3 11.6 11.7 12.6 12.4 12.4 - - - 12.3 11.7 12.6 12.1 11.1 11.6 11.8
RENJU - - - - - - - - - - - 5.1 5.0 5.2 3.2 -
SPEUL - - - - - - - - - - - 3.1 4.4 4.0 - -
STRJO - - - - - - - - - - - 4.6 4.6 5.1 - -
- - - - - - - - - - - 5.1 4.5 5.0 - -
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Sum 19.1 11.6 19.8 16.1 26.1 19.9 8.2 8.0 7.6 12.3 18.8 34.7 39.9 40.7 14.8 11.8
3. Results (Meteors)
====================
July 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
--------------------------------------------------------------------------------
BENOR - - - 6 - 13 25 27 28 23 - 12 10 7 12
MOLSI - - - - - - 16 19 - 2 18 - - - 21
- - - - - - - - - - - - - -
NITMI - - - - - - - 8 13 - 3 15 - - -
QUIST 36 27 - - - 8 42 37 35 51 37 47 10 42 39
RENJU - - - - - - - - 9 - - - - - -
SPEUL - - - - - - - - - - - - - - -
STRJO - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - -
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Sum 36 27 - 6 - 21 83 91 85 76 58 74 20 49 72
July 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
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BENOR 8 - 7 - 20 17 12 17 7 - 22 - 4 - - -
MOLSI - - 3 19 36 - 2 - - - - 44 17 38 - -
- - - - - - - - - - - - - 12 - -
NITMI - - - - - - - - - - - - - - - -
QUIST 34 41 39 25 32 50 - - - 29 71 69 64 38 50 36
RENJU - - - - - - - - - - - 26 19 23 15 -
SPEUL - - - - - - - - - - - 20 42 26 - -
STRJO - - - - - - - - - - - 33 60 44 - -
- - - - - - - - - - - 19 28 14 - -
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Sum 42 41 49 44 88 67 14 17 7 29 93 211 234 195 65 36
Sirko Molau, 2002/08/15