I have a simple question, dealing with a problem of population index determination :
In "Meteors showers and their observations", NAMN Guide, chapter 7,
we find :
"r is a value indicating how many more times meteors of magnitude m+1
appear than meteors of magnitude m. [..] Example : m=4, r=3 => tree times
as many meteors of magnitude 5 appear than meteors of magnitude 4".
I conclude : r = n(m+1) / n(m),
where n(m) is the number of meteors of magnitude m. I call this method
method 1
On the other hand, in "The Perseid meteoroid stream : characterization
odf recent ectivity from visual observations", Brown & Rendtel, Icarus,
124, 414-428, 1996, we can read :
"r=N(m+1)/N(m),
where N(m) is the TOTAL bumber of meteors of magnitude m OR LESS."
Whith this definition, we have :
N(m) = sum(n(m)), with m < smallest magnitude sawn
and r = N(m+1) / N(m)
I call this method method 2.
These 2 definitions are completely different and lead to different value of r.
Now, lets take a concreate example :
In "Comparison between Leonid meteor shower observation during 1998-200",
PSS, 50, 379-384 (2002), table 2 : lets try to compute r just from the
first line :
m = 4.5
0.5 -3.2
n(m) = 33 10
10
value of r = 1.76
Now the question is : where does this value 1.76 come from ? Is it an
average value ? I suppose yes, but averaging what ?
Method 1 leads to r = 33/10=3.3 and 10/10=1. average is 2.15
Method 2 leads to r = (33+10+10)/(10+10)= 2.65 and (10+10)/10 = 2.
average is 2.33
So before I ask the author (who is perhaps here...), I would ike to
be sure of what I am speaking of.
Last question : is it scientificly correct to compute an average value of r, if there is not so many meteors, and so a great scattering in the values of r ? I ask this, because I would like to compute r from our video observations...
Thanks a lot for any answer, and clear skies !
Jeremie
-- ************************************************************ * Jeremie VAUBAILLON * Institut de Mecanique Celeste et de Calcul * des Ephemerides (www.bdl.fr) * 77 Avenue Denfert Rochereau * 75014 PARIS * FRANCE ************************************************************ * tel : +33 (0)1 40 51 22 66 * fax : +33 (0)1 40 51 20 58 * URL : http://www.bdl.fr/Equipes/GAP/equipeGAP-JV.html ************************************************************