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(meteorobs) ZHR calculations
Thank you, Marco, very much for the detailed description of how you determine
ZHRs. Let me add a few remarks on different approaches.
The r-values in 1996 are definitely lower than 2.0. I did not find any kinks in
the magnitude distributions indicating two r-values over the magnitude range,
i.e. two meteoroid components. This may certainly change if more data are
available for the specific period between 4 and 5 h UT.
When computing r-values it seems quite important which perception probabilities
are used. I use the probabilities determined by Koschack & Rendtel from
so-called double count observations totalling a few thousand meteors. These
obervations show that p=1.0 for meteors brighter than 7.5m difference from the
lm. (At lm=6.5 a -1m meteor has p=1.0) So this is quite different from what
Kresakova got. This might even cause a kink in the magnitudes appear when
applied in stead of the p of Koschack & Rendtel. Well, who knows which p are
correct...?
Norman, your Cp has been determined also in past IMO analysis and constantly
found to be a little lower than 0.5, This well agrees with what Marco found.
Well, Marco, it is most striking that your sporadic rate peaks at the time like
the Leonids did, with an HR of over 70! As you report 20 meteors in a 17-minute
period, this cannot be explained by Poissonian, you know the error is
HR/sqrt(n), i.e. about +- 15. I think that this is the proof that Cp can be most
variable even in short periods. You were certainly highly alerted under the nice
Leonid display, which is not expressed in a high lm. And what helps a Cp=1.2 if
it is +-0.5?
What I found is that there is more power in AVERAGING MANY OBSERVATIONS than in
introducing one or another correction factor. The power of statistics lies in
large sample numbers. This is basically the intention of an International Meteor
Organization. When you have a large sample of all kind of Cp in your data set,
you get the right value, without adventurously putting factors in the data. On
the other hand, I do admit that this is not always available, of course.
As to zenith correction and exponent, the unique chance to have data of Europe
and America of the same time allowed an estimate of gamma for the Leonid
maximum, and I found 0.8! There is no physical theory explaining gamma<1.0, but
the result supports the fact that it's not >1.0. Actually, your own impression
of a varying gamma might be used as a pro to this assumption.
The recent Leonid article can be found at
http://www.tu-chemnitzdot de/~smo/imo/news/leo96.html
Finally, as to observers anlysing their data: I fully agree with Marco. Making
something of one's own observations is much more satisfying than just filling a
hungry database far away. Moreover, too few people actually realize that the
database of IMO can be used by others too.
Now, it got a little longer ... anyway, best wishes, Rainer