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RE: (meteorobs) Moonlight and the IMO method

Just a comment, I was well placed to separate the Taurids from Leonids (I 
won't try and speculate about Apex meteors) and only saw 4 in 6.5 hours.

Wayne

----------
From: 	Wesley Stone[SMTP:wes_stone@altavista.com]
Sent: 	Tuesday, November 21, 2000 3:29 PM
To: 	meteorobs@jovian.com
Subject: 	Re: (meteorobs) Moonlight and the IMO method

On Tue, 21 November 2000, Rainer Arlt wrote:

> I would tend to say that the low sporadic rates are mainly due
> to the fact, that the Leonid radiant is so close to the apex
> area from where a considerable number of sporadics come in the
> last morning hours -- just when observers were out for the
> Leonids. As we had to face a direction not favourable for radiant
> association -- because of the Moon -- it is very likely that a
> number of sporadics was simply counted as Leonids. I found my
> own notes of 17/18 with a single sporadic in about 1h effective
> time!

I agree; the apex meteors probably polluted the Leonid numbers to some 
extent (1-2/hour?).

Speaking of which: I'm not experienced in interpreting unguided wide-field 
photos, but can anyone confirm that the "Leonid" on the Sky and Telescope 
web page "news" report is not a Leonid? Plotting points on a gnomonic map, 
it looks like the backward trace misses the radiant by a goodly distance to 
the north:

http://www.skypub.com/news/images2000/001118news01.jpg


> It may be interesting to compare this effect (of depleted sporadic
> numbers during major-shower maxima) among the major showers
> QUA, PER, LEO and GEM with respect to their different distances
> from the apex. The GEMs should affect the sporadic rate least.

I think sporadic pollution may be more of a problem when shower rates are 
low. I remember getting sporadic rates of 31/hour during the 1997 Perseids 
(103 Perseids in same hour), 25/hour during the 1993 Geminids (73 Geminids 
in same hour), and 28/hour during the 1999 Leonids (73 Leonids). These were 
all during morning hours with excellent LM (~7). Perhaps sporadic rates get 
polluted with shower meteors during high rates. In looking at old reports, 
I think you'd have to investigate whether the observers separated out the 
minor showers. If Aquarid complex meteors are counted as sporadics during a 
Perseid observation, or Taurids counted as sporadics during the Leonids 
(which is probably just as well), the sporadic rates for those observers 
will be higher.

--
Wes Stone
Portland, OR

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