(meteorobs) Origin of ZHR?

[Julian Parks]

Under Section 15.6, Zenithal Hourly Rate, and Zenithal Magnitude, 
p.202, the 1955/1957 ed. of Sedgwick's, " Observational Astronomy for 
Amateurs," and I quote,  "The ZHR is derived from the observational 
data by applying corrections for the altitude of the radiant and for 
moonlight, if any; generally, however, observations for statistical 
purposes are not made when there is strong moonlight."  
 
"If R is the observed hourly rate, then Rc (the HR corrected for 
radiant altitude a) is given by 
 
                        Rc = R cosec (a+6º)
 
The correction for moonlight depends upon the lunar phase and the 
incidence of diffusing matter in the atmosphere, and must be 
determined empirically by comparing the numbers per magnitude with 
similar figures relating to a previous, moonless, return of the 
swarm."  End quote.
 
Julian Parks
Rego Park, NY




--- In meteorobs at yahoogroups.com, meteors at ... wrote:
>
> Julian,
> 
> >From what I've been able to determine, Opik, Porter, and Oliver all
> addressed parts of the issue, so maybe Sedgwick is the one who put 
it all
> together. I'll check my County Libtary for the bood.
> 
> Is there a copy of the formula?
> 
> Wayne
> 
> 
> > Rich,
> >
> > If you have a copy of Sedgwick's, "Observational Astronomy for 
Amateurs,"
> > either the 1955/1957 edition or the fourth edition there is a 
reference to
> > Meteor Counts and Hourly Rates in Section 15.5 and to Zenithal 
Hourly
> > Rate, and Zenithal Magnitude in Section 15.6 and a Bibliography 
for E.
> > Opik, J.G. Porter, C.P. Oliver, et. al. who researched this 
area.  From
> > the Bibliography the dates I see referred to are 1920, 1921, 
1923, 1930,
> > 1931.  These cites are from the Harvard Circ. and ``Journal of 
the British
> > Astronomical Association among others.  There is also mentioned 
in Section
> > 15.5 statistical work in the mid-nineteenth century by a Gravier 
and
> > Schmidt.  Whatever that statistical work is I do not know.  
Sounds like a
> > trip to the library.
> >
> > Hope this helps.
> >
> > Julian Parks
> > Rego Park, NY
> >
> > ----- Original Message -----
> > From: "Richard Taibi" <rjtaibi at ...>
> > To: <meteorobs at ...>
> > Sent: Friday, May 11, 2007 9:02 PM
> > Subject: (meteorobs) Origin of ZHR?
> >
> >
> >> Does anyone know who developed the concept of the Zenithal 
Hourly Rate,
> >> and
> >> when it was proposed?
> >>
> >> Thanks!
> >>
> >> Rich
> >>
> >>
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