[Prev][Next][Index][Thread]
(meteorobs) Re: [IMO-News] eta Lyrids
NOTE: Again, Marco is not a 'meteorobs' subscriber. Please be SURE to "Cc:" his
address 'marco@rulpre.LeidenUnivdot nl' in any replies you send on this thread!
Lew Gramer <owner-meteorobs@jovian.com>
------- Forwarded Message
To: imo-news@egroups.com, molau@informatik.rwth-aachendot de
Cc: marcolan@stad.dsldot nl
From: "Marco Langbroek" <marco@rulpre.LeidenUnivdot nl>
Date: Mon, 15 May 2000 17:28:43 +0100
Subject: Re: [IMO-News] Re: eta Lyrids
Sirko wrote:
> Maybe you misunderstood me: I was not going to say that what the visual
> observers saw was an illusion.
> Carl and Rainer asked me to check whether I
> find these eta Lyrid meteors in my video data. I did that, but I found not
> a single member in these two nights even though the geometry was quite
> favourable, i.e. I observed at only little distance from the
> supposed radiant.
> Our video data have helped to examine the true nature of the 'xi Bootids',
> for example, but in this case we seem to have less fortune. That's all I
> wanted to let you know with my previous posting
Hello Sirko,
I got a bit stingy because whenever video data enter the field people
seem to tend to jump to the conclusion that these settle the issue.
That's not your fault of course, but still it is what happens. In
some cases, video indeed has done a fine job. But video also
has its drawbacks, and there is the matter of sample size. Video
observations just do not necessarily overrule visual reports just
because they are from video cameras instead of humans that can err.
In the case of eta Lyrids, which are a minor stream (which means:
few meteors, also for video cameras), and a stream actually
observed now for several years (this years observations are not the
first mentioning of the stream), I really don't think 50 sporadic video
meteors among which you expect few members of a minor stream like
this have much to say. Your intro to your mail (actually, I was not even aware
of the
'discussion' you mentioned expect for 2 of the the private mails between Carl,
Rainer and you I got) and its content did suggest to me that your
data should imply that there has most likely been no true activity;
and this made me stingy simply because as mentioned I have noted that
there is a tendency to take whatever has "video" involved as very decisive and
unproblematic, notwithstanding the fact that video cameras can also
suffer from low sample sizes (just as do visual observers of
course!), are biased in recording streams with differing population
indexes, and nothwithstanding that transforming video records into
real flux rates is so far still problematic.
In the current context, I thought I should remind people of that. Not
because I think video would have little to say (actually, I think
video is one of the most informative new techniques that arrived
last 15 or so years within meteor observing and should be taken very
serious. At the same time, I urge video explorers not to get into the
trap of becoming too overconfident in their technique. The discussion
on the "drop-off" in the fainter portion of the Leonid magnitude
distribution is a case at hand. I really think video failed there and
possible detection bias by the cameras and recording technique was
not properly taken into account), but because I feel that sometimes video data
are presented too uncritically as 'unproblematic', or at least are
too often taken as such by the 'consumers' of video reports. Every
technique has its drawbacks and problems and that should be acknowledged.
Allright, I've made my point I guess. It has been a long warm day
here.... So lets cool down this discussion.
Marco
- ----------------------------------------------------------
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
- ----------------------------------------------------------
- ------------------------------------------------------------------------
Remember four years of good friends, bad clothes, explosive chemistry
experiments.
http://click.egroups.com/1/4051/10/_/70339/_/958404517/
- ------------------------------------------------------------------------
To unsubscribe from IMO-News, send a blank message to
imo-news-unsubscribe@egroups.com, or visit
www.e-groups.com/list/imo-news.
- ------------------------------------------------------------------------
------- End of Forwarded Message
To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html