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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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