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Re: (meteorobs) Request for data
Lew wrote about lm and meteor magnitude estimates:
>I think the analysis you're attempting will end up being
>complicated by this mixture of observing methods
Extinction is as low as about 0.25mag at 30deg elevation. This is still
lower than the best estimates you can make. I guess most observers would
not use stars lower than that for comparison. Another effect is much more
important: A meteor at 30deg elevation has twice the distance than a meteor
in the zenith. Its intensity is only a fourth (well over one mag fainter).
The loss of meteors due to the distance is roughly balanced by the
increasing volume being loked through when looking at lower elevations. It
dosn't work of course for all heights. Hence, the recommendation is to use
a field of view no lower than 50deg in the sky. Otherwise, the population
index r and the ZHR will be affected by the magnitude shifting.
I have seen meteor reports with magnitudes corrected to absolute magnitude
(meteor in the zenith). This correction is not necessary because of the
balance mentioned above.
Rainer Arlt
---------------------------------
Visual Commission
International Meteor Organization
email: visual@imodot net
Homepage: http://www.imodot net
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