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Re: (meteorobs) Re: Where to look for LM Counting Areas
>>IMO LM count areas should be chosen as close to the ZENITH as possible!
>Lew, this is possible but it is totally incorrect.
Bob, I know you're gonna *KILL* me for quoting Rainer Arlt at you... But
just to clear up any misconceptions, here's an archive of one of his 1996
messages to 'meteorobs'. (Note this thread demonstrated the healthy
diversity of opinion that always persists in meteor observing: 3 different
*experienced* IMO observers described 3 different methods for LM estimate!
George repeated Bob's recommendation above, Rainer stated the following,
while Graham Wolf recommended something totally different! This may be
confusing, but there's something to learn from all these techniques for us
less experienced folks):
Message # 01427:
(meteorobs) Limiting magnitude
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* To: Meteor Observers List <MeteorObs@latrade.com>
* Subject: (meteorobs) Limiting magnitude
* From: Rainer Arlt <100114.1361@CompuServe.COM>
* Date: 30 Aug 96 16:46:49 EDT
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Let me tackle the limiting magnitude problem: First, from the theoretical
side:
An observer not looking at the zenith should see less meteors than somebody
looking to the zenith because the meteors are farther away and, hence,
fainter.
However, it turned out that the loss due to larger distance plus extinction
approximately balances the increased volume the observer looks through (and
sees
more meteors in therefore). This would mean that the limiting magnitude should
not contain the extinction, i.e. it should be estimated in the zenith.
(This is
also what the Visual Handbook says in paragraph 2.5.2.)
Now for the practical side: You know extinction can vary greatly. Moreover,
star count areas are not in the zenith generally. So you may use any fields
down to
50deg without problem. And please don't start another discussion because you
once chose a field at 40deg elevation---it's ok (extinction is about .1mag
there). If it is really hazy and you endeavour to observe, you will
automatically choose a field close to the zenith where the sky is best, and
you
will not have the problem with an incorrect balancing as said above.
Rainer
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Message #01428:
Re: (meteorobs) Limiting magnitude
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* To: Meteor Observing Mailing List <meteorobs@latrade.com>
* Subject: Re: (meteorobs) Limiting magnitude
* From: Lew Gramer <dedalus>
* Date: Fri, 30 Aug 96 16:56:42 -0400
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>This would mean that the limiting magnitude should not contain the
extinction,
>i.e. it should be estimated in the zenith. (This is also what the Visual
>Handbook says in paragraph 2.5.2.)
Thanks for clearing up the issue, Rainer...I've been intentionally choosing LM
areas near my field of view, and even including ones below 40o if I felt my
attention was concentrated down there! Good thing you mentioned this... :<)
I'll make sure I get ahold of the latest IMO Handbook soon!
...
Lew
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