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Re: (meteorobs) Bob Lunsford's Suggestions/Help & Nov. 19/20 Correction
Happy Thanksgiving to all our American members..
... just wanted to add a comment....
A third, and excellent (and IMHO, the best) source for LM tables, maps, etc
can be found at: http://www.seds.org/billa/lm/..
For each star area and table, there is a link to a wonderfully illustrative
star map of that area...
that's my 2 cents on the matter,
Joseph
San Diego, CA
----- Original Message -----
From: "RainerArlt" <rarlt@aipdot de>
To: <meteorobs@atmob.org>
Sent: Wednesday, November 26, 2003 11:02 PM
Subject: Re: (meteorobs) Bob Lunsford's Suggestions/Help & Nov. 19/20
Correction
> Hi Mark and all observers,
>
> Your report was well received and looks fine. Let me
> comment on a subject that is not widely noticed, just
> because your LM list is a good example.
>
> > LIMITING MAGNITUDE:
> >
> > STAR STAR
> > TIME AREA COUNT LM
> >
> > 7:06 4 7+ 5.1+
> > 7:06 8 9 5.5
> > 7:27 4 7+ 5.1+
> > 7:27 8 ~10 5.9
> > 7:50 4 ~8 ~5.3
> > 7:50 9 6 -
> >
> > MEAN LIMITING MAGNITUDE: ~5.4
>
> At low limiting magnitudes, there are severe gaps in the
> conversion tables from star count to LM. This is of course
> since not every tenth of a magnitude is 'occupied' by a star
> in the count area. You will often encounter a significantly
> lower LM in one of the counts made the same time. A count
> in area #4 of 7 stars may be 5.1, but since the next star is at
> something like 5.8, the LM could have been also 5.2, 5.3, 5.4,
> ... 5.7 with the same count in #4.
>
> I'd suggest to use the highest count for each time and average
> these (unless LM better than say +6.0). In your example, this
> would come down to
>
> 07:06 5.5
> 07:27 5.9
> 07:50 5.3
>
> AVERAGE 5.57
>
> The method of course requires that enough star counts are made
> during the observation and that -- most critically -- several
> areas are counted.
>
> Please note also that updated LM conversion tables based on
> the Tycho catalogue are available at
>
> http://www.imodot net/visual/lm.html or
> http://www.amsmeteors.org/imo-mirror/visual/lm.html
>
>
> Best wishes,
> Rainer
>
> --
> Rainer Arlt -- Astrophysikalisches Institut Potsdam -- www.aipdot de
> Visual Commission - International Meteor Organization -- www.imodot net
> rarlt@aipdot de -- phone: +49-331-7499-354 -- fax: +49-331-7499-526
>
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