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Re: (meteorobs) ZHR of meteor showers II
A ZHR of 270.5 implies an accuracy that is basically impossible in visual
observation. It wouldn't surprise me that this should more correctly read
300 +/- 200. One can derive a formal error based on the sqr root of the
number of shower meteors seen, but this is the absolute minimum for what
the true error is and assumes that there are no errors in assigning shower
association. Every manipulation of the data, in correcting for the lim
mag, radiant elevation, perception coefficient, field obscuration by cloud
etc intruduces additional error. But ultimately, the biggest error is the
observer's subjective assignment of values to the observed quantities;
shower association, meteor magnitude and limiting magnitude.
Only the significant figures should be quoted in the final result and
there is no value in claiming greater accuracy than the observations
allow. A figure of 300 +/- 200 should not be seen as bad observation or
as of no value, but as (possibly) a more valid representation of the
available data. When the observations are combined with the data from
many others, the overall error can drop dramatically, and then the
intercomparison of individual observations with this combined result can
indicate the magnitude of the error in the individually derived rates more
reliably.
Note that "error" is just as important a calculated value as the ZHR value
it is related to. It is not "incorrectness", and nobody should feel
afraid of quoting a large error when this what the data implies. The
example of the error I use above is purely hypothetical and is not
actually calculated from the observed data. Too often there are arguments
about what the TRUE ZHR is for some shower maximum when the problem is
probably more one of the error values
Cheers, Rob
Robert H. McNaught
rmn@aaocbn.aaodot gov.au
On Fri, 17 Dec 1999, Martin Galea De Giovanni wrote:
> Hi,
>
> Yes Michael , I have been discussing this strange observation as regards to
> the ZHR calculated . I guess that the Method which IMO uses is the one
> using the magnitude distribution could hopefully solve the problem . I have
> calculated it using Metshow , which does not take into account the
> magnitude distribution .
>
> The thing is that all the observers below are mostly experienced observers
> who have been observing for more then 10 years in most cases.
>
>
>
> If anyone has any suggestion or comment they are most welcome to send it!
>
> Martin
>
>
> At 11:53 17/12/99 , you wrote:
> > > obs. date beg time end time teff lm GEM ORI MON HYD SPO TOT ZHR GEM
> > > [UT] [UT] [min][mag]
> > > -------------------------------------------------------------------------
> > > Team A
> > > GALMR 13-14 21:45 04:00 375 5.8 408 9 4 1 40 462 135
> > > TANTO1 13-14 21:40 22:35 54 5.1 37 # # # 6 43 194.5
> > > TANTO2 13-14 22:54 23:42 47 5.1 48 # # # 4 52 253.1
> > > TANTO3 13-14 01:22 02:23 59 5.1 63 # # # 10 73 270.5
> > >
> > > Team B
> > > FORMI 13-14 21:46 01:16 180 6.0 128 # # # 22 150 73*
> > > ZAMJO 13-14 21:47 01:16 179 6.1 196 # # # 32 228 101*
> > > PACAL1 13-14 21:41 22:25 43 5.9 25 # # # 11 36 77
> > > PACAL2 13-14 23:15 23:58 42 5.9 16 # # # 10 26 43
> > > PACAL3 13-14 00:00 00:45 44 5.9 17 # # # 5 22 52*
> > > * ZHRs marked with a * have had corrections since last reports due to more
> > > accurate obscuration values
> >
> >
> >That's that problem, what I have wrote about. Different observers
> >report a different ZHR in the same time. How to correct this
> >observation (how does it IMO?). Can somebody recommend me some paper
> >or book about this problem?
> >Thanks Michal
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>
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