Forward Scatter Meteor Observations of Geminids 1998
Observer: Ton Schoenmaker
E-mail: schoenmaker@nfra.nl
Location: Roden, Netherlands (06 26' E, 53 08' N)
Frequency: 72.11 MHz
Transmitter: Wroclaw, Poland; 120 kW, horizontal polarization;
distance 756 km; at least one other unidentified transmitter
Antenna: 4-element horizontal Yagi, geographical azimuth 105 degrees
(ESE), elevation 15 degrees
Receiver: home-made convertor followed by Barlow-Wadley XCR-30 Mark II;
total sensitivity 0.3 uV for 20 dB S/N, bandwidth 4.5 kHz
Observing: rectified signal from 455 Khz IF recorded with a Servogor
stripchart recorder with a chart speed of 120 mm/hour
Compared to the recent Leonid observations, much less long-duration reflections were present in the Geminid registrations. Only during the apparent maximum on 14 December between 6h and 10h UTC long-duration reflections were prominent. If these reflections may be considered as "the" maximum then it occurred around 14 December 1998 at 7 +/- 1 h UTC (solar longitude 262.1, J2000.0). A maximum of weaker reflections with hardly any long-duration reflections took place earlier that night on 13 December at 20h UTC (solar longitude 261.6, J2000.0). After corrections for the observability function this secondary maximum is still very distinct.
In the following table the uncorrected hourly counts for signals stronger than 0.1 uV are given. Between brackets the hourly percentage of total reflection time, also for signals stronger than 0.1 uV.
| December 1998
UTC | 11 12 13 14 15
---------------------------------------------------
00 | - 31 65 116 63
01 | - 41 66 125 40
02 | - 58 43 83 44
03 | - 73 72 102 52
04 | - 75 53 89 49
05 | - 57 43 93 ( 3%) 59
06 | - 95 79 95: (21%) 69
07 | - 98 88 66: (50%) 61
08 | - 69 91 116: (35%) 46
09 | - 78 83 98: (18%) 57
10 | - 59 54 82 ( 4%) 60
11 | - 64 - 61 33
12 | - 36 - 47 35
13 | - - - 24 37
14 | - - - 36 27
15 | - - - 45 21
16 | - 60 82 51 19
17 | 16 72 86 69 -
18 | 55 95 123 69 -
19 | 59 97 144 84 -
20 | 56 79 175 83 -
21 | 66 76 144 84 -
22 | 48 69 97 78 -
23 | 33 44 68 70 -
---------------------------------------------------
UTC | 11 12 13 14 15
| December 1998
- no observations
: hourly counts affected by long-duration reflections
Figure 1. The hourly counts of the Geminids on 11 - 15 December 1998. The left arrow points to the observed maximum of weak reflections. The right arrow points to the maximum of long-duration refelctions. During this maximum (about 50% total reflection time between 7h and 8h UTC on 14 December) the hourly counts were reduced because of the large amount of dead time.
Hello everybody,
Last weekend I tried to observe the Geminids.
Friday I went to my new observing site at the feet of Yamanota
'mountain' early to observe some variables. Around 21h30 local time the
Geminid radiant started to rise, but I continued observing variables
because of the low radiant elevation. While I was doing this, I observed
four Geminids, one of +1 (very long trail!) and three of about +3/+4.
While the radiant was rising, the cloudcover was increasing. When the
radiant was high enough, I couldn't observe Geminids anymore. There were
only some tiny holes in the cloudcover, and the clouds didn't disappear.
Saturday was totaly cloudy. There were even some rain.
Sunday didn't look very promising either. At 21h30m I gave up hoping for
better weather, so I decided to get a beer from the freezer. Wrong
decision! At 22h00m the cloudcover started to disappear. A few minutes
later there were no clouds anymore! My wife and I started some
'astrotourism' from ou garden. We saw some very nice Geminids. While my
liver was digesting the alcohol of the one beer I drank, I was wondering
whether I should go to my observing site. Next day I had to work again.
At 22h45m I couldn't resist the temptation anymore and I left for the
Yamanota.
When I arrived there, some clouds started to rise from the east. But
they renained I minor nuisance. Mostly the cloudcover was between 10 and
30%. Only 5 minutes of observations were hampered by a cloudcover of 40%.
At 23h30 local time I started the two hour observing session. The
Geminidshow was not so spectaculair as the Leonidshow of a month ago.
But then again, will any meteordisplay be so spectaculair as the
Leonidshow? But even considering this, I had the impression that the
activity was lower than it should be, so close to the predicted maximum.
Or did the Geminids peek earlier (or later) than expected? During my
observations I had the impression that there was something weird with
the magnitude distribution. I had the impression that there were many
Geminids brighter than +2, and many Geminids weaker than +3. But in the
magnitude distribution I've made today, this impression is not (so
clearly) visible.
At 1h30 local time I stopped observations because I had to rise at 6
o'clock for my job again. But the day after tomorrow my two-and-half
weeks X-mas holidays start. If the weather cooperates, I will do some
more meteor observations the coming weeks. Let see if can spot some
Ursids from Aruba. The radiant rises early in the morning, so early to
bed and early up again! You'll here from me!
Observer : Erwin van Ballegoij
Location : Yamanota, Aruba, Dutch Antilles
Coordinates : 12 degrees 29' North 69 degrees 57' West
Date : December 14 1998
Time (UT) Teff F Lm GEM PUP HYD SPO TOT
03:30-04:30 0.83 1.25 6.00 37 1 0 2 40
04:30-05:30 0.83 1.27 6.15 43 1 1 7 52
80 2 1 9 92
Plots also checked for COM, XOR, MON and PHO, but none found.
Magnitude distribution:
-2 -1 0 1 2 3 4 5 6 mean M
GEM 2 6 11 7 13 13 11 14 3 2.43
PUP 0 0 0 0 0 0 0 0 6 6.00
HYD 0 0 0 0 0 1 0 0 0 3.00
SPO 0 0 1 1 0 2 2 1 2 2.56
Yours,
Erwin van Ballegoij
**********************************************
* Erwin van Ballegoij en Heidi van der Vloet *
* Tarabanaweg 9 *
* Oranjestad, Aruba *
* tel: ++ 297 821918 *
* e-mail: ballegoy@setarnet.aw *
**********************************************
