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(meteorobs) Re: [IMO-News] eta Lyrids
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Lew Gramer <owner-meteorobs@jovian.com>
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To: imo-news@egroups.com, molau@informatik.rwth-aachendot de
Priority: normal
From: "Marco Langbroek" <marco@rulpre.LeidenUnivdot nl>
Date: Mon, 15 May 2000 15:41:43 +0100
Subject: Re: [IMO-News] Re: eta Lyrids
Hello all,
Just to put these video results into a proper context:
As a comparison: the sample size (numbers of (non-eta) meteors
observed) by the Dutch observers (at least 3 persons so far at two
locations) that reported activity of the stream on May 5-6 and 6-7
are an order of a magnitude LARGER than the sample size Sirko reports
for his video camera below. For example, I had a similar number,
visual observed, as to what Sirko reports for his two observational
nights (50) during the night of 6-7 May alone (twilight data not
included). If I compare and scale my counts from 5-6 May (in closest
agreement in solar longitude and thus distance from the maximum to
Sirko's sample) to Sirko's video counts and assume streams and
sporadics would show up in similar proportions (which they do not
probably, due to r-value differences), then I would expect Sirko to
have between 3 to at best 5 eta Lyrids roughly in his sample, in
other words: not much, to be clear. That
is: under above assumption, and if r-values of sporadics and the
stream differ, stream members could be either over- or (and that
should be taken well) under-represented in his video sample.
Apparently, he has not 3 to 5 eta Lyrids, but none. Well, that's one
small video camera sample against 3 visual observers (and I understood the
Rumanians
also saw something). If Sirko used his automatic detection software
again (did you Sirko) he might have missed the fainter meteors in
addition.
This just to put things in the proper context as far as this
video-visual data comparison is concerned, and avoid jumping to
conclusions when 'objective' video data are contrasted with 'biased'
observers data. Actually, I think that the fact that Sirko's camera
apparently recorded no meteors from this shower, is a pity, but given
his sample size has little conclusive value with regard to the
question whether the stream has been active or not.
Marco Langbroek
Sirko Molau <molau@informatik.rwth-aachendot de> wrote on Mon, 15 May 2000
11:05:08 +0200
> in the last few days there have been discussions on possible activity
> caused by debris from comet IRAS-Araki-Alcock (eta-Lyrids). In the
> nights of May 4/5 and 5/6 my video camera AVIS was operated at the
> Al-Azraq meteor camp in Jordan. Even though we had some interference by a
> sand storm and a few clouds earlier these nights, we were able to observe
> the eta-Aquarids visually in the mornings hour, and also to obtain about 6
> hours of video recordings. Thanks to the good limiting magnitude a little
> more than 100 meteors were recorded at that time, less than half of which
> belonging to ETA shower. From the remaining ~50 meteors not even one came
> from the suspected Lyra radiation area.
----------------------------------------------------------
Marco Langbroek
Faculty of Archaeology tel. +31 71 5272930/25
Leiden University fax +31 71 5272928
P.O. Box 9515 m.langbroek@arch.leidenunivdot nl
NL-2300 RA Leiden
The Netherlands
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