(meteorobs) Serious problem about analysis!

[RainerArlt]

Hi all,

Thanks Pavol for clarifying the question already.

> >   As we know, there is a calculator:
> > ZHR = (1 + sum n) / sum (Teff/C)
> > and my method is, sum all the observers' n, and sum
> > all the observers' Teff/C, then recive a ZHR at last.

Let me also add that this way of averaging ensures
that the observations are automatically weighed by
their total correction. Largest corrections get the
least influence.


> > e.g. Observer A, lm=5, n=2; observer B, lm=6, n=4.
> > F=1, Teff=1, h=90, r=2.
> > 
> > My method: ZHR=6.6+-2.5.
> > Zhu's method: [ZHR(A)+ZHR(B)]/2, ZHRave=7.8.
> > Because ZHR(A)=8.5+-4.9 ZHR(B)=7.1+-3.2, Zhu thoughts

This last line is definitely wrong. The +1 always
refers to the sum of all observers. It is an effect of
small numbers n, as Pavol explained. So it vanishes
for large n. It should NOT BE ADDED TO ANY INDIVIDUAL n!
Then you create lots of meteors. You can either do

(1+2+4) / (0.354 + 0.707) = 6.6 as you were doing it, or

ZHR(A) = 2 * 2^(6.5-1.5) = 5.6
ZHR(B) = 4 * 2^(6.5-0.5) = 5.6
avg(ZHR) = 5.6
This value will come close to the first version, if a
lot of data is involved. Nevertheless, note that it does
not weigh the observers by corrections (here accidentally
irrelevant).

The individual ZHR=6.6 as taken from (1+n) has very little
meaning and is only valid of no other data are avaliable.
It is then the best you can say about the ZHR. But it is
not the basis of averaging!

> Zhu is right! But... he must accept, that he count ZHR for
> THE ONLY observer! If two observers observe, you know that
> they observe together ... 
>   If you count ZHR for a few number of observations, it is 
> better use average value, or weighted average value (weight 
> is statistical error... the higher error the less contribute to
> result). If you count ZHR for 100 periods, you have at least 
> 10 meteors and there 1 meteor doesn`t play a role.

Ok, Pavol, I see you were saying the same -- I have put
it in some numbers. Maybe they help.

Best wishes,
Rainer


-- 
Rainer Arlt  --  Astrophysikalisches Institut Potsdam -- www.aip.de
Visual Commission - International Meteor Organization -- www.imo.net
rarlt at aip.de --  phone: +49-331-7499-354  --  fax: +49-331-7499-526