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(meteorobs) Rainer Arlt's Comments on Nov. 19/20 Correction
November 29, 2003
Greetings Rainer Arlt and Fellow Meteor Enthusiasts!
Thank you for all of your comments regarding my LM
situation and everyone else.
Thus, I will try to revise the way I record the LM.
Ever since I started using star areas, I had felt more
comfortable recording the LM. I knew there were
problems with using star areas, but now with
everyone's input on the topic, I must say it gets a
tad confusing on what way is the tried and true,
preferred way. Many of the problems other observers
have had with star areas are the same with me, but I
will keep using them (with your suggestions) and maybe
"experiment" with some other ways.
Thank you again for the appreciated insight.
Big and bright, rocky Geminids!
Mark Fox
Newaygo, MI USA
--- RainerArlt <rarlt@aipdot de> wrote:
> 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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