[Prev][Next][Index][Thread]

Re: (meteorobs) leonids storm




[From Lew, the meteorobs list administrator: Please note Hartwig
 is not a current subscriber to 'meteorobs'! If you reply to his
 message, be sure that 'fb4a042@botanik.botanik.uni-hamburg.de'
 appears in your "Cc:" line!]


Khaled M. Tell wrote today: 

> I have recently viewed the imo leonid meteor storm simulation(
> metsim)and I was very much impressed with the program which was
> carefully made and accurately simulating a meteor storm.

Yes, Sirkos program is indeed very nice. 

> the program convinced me that I could not count that much of meteors if
> the rate is over 10 meteors per second. ( which counts to  36000 meteors
> / hour ). it seemed to me that the eye and the brain could not count and
> even follow such high numbers of meteors. so the program left me
> helpless. 

I completely agree that one cannot COUNT more than 5-6 meteors per second.
Nevertheless one can roughly ESTIMATE such rates. Turn on metsim, simulate
10 meteors per second and the 50 meteors per second. There is a hige
difference. 

What we found helpful was to open the eye for 1s intervals (or imagine 1s
time intervals) and to guess or estimate how many meteors were seen in
this interval. Averageing estimates from several intervals (one can do
that roughly without calculation from time to time) will than yield
something like a rate estimate (25/s, 50/s). The typical error was about
30% or even less. Sirko and I have published a paper in a recent issue of
WGN. 

> moreover, I tried to test the method suggested by the imo, that is to
> change to ten meteors count and replace them by one beep instead of
> counting, but it appeared to me that this method is not practical to me
> with the presence of high numbers of meteors.

I think that method will work fine if you have a rate of, say, 1-2 meteors
per second. Due to apparent statistical clustering the distribution will
seem inhomogenous. So you will have e.g. 2-3 seconds without any meteor
and then 4 meteors almost simultaneously. In such a situation this method
may work very well. At  30 meteors per second this method will fail since
it depends on accurate counting individual meteors, which is of course not
possible. 

> moreover, in the sky, meteors will be distributed all over the sky
> heading north, south, west, and east, so one may miss some meteors. but
> in the program, one can see all meteors coming, although he can not
> count them all.

Yes. The observer will notice a larger percentage of faint meteors at the
center of his field of vision than in the periphery, where he may only
notice the really bright ones. 

However, ZHR is normally defined as a single observers4s rate, and of
course any single observer will always only perceive only a fraction of
the meteors present in the sky. 

You are right, of course, that one of the limitation of a simulation
program is that it cannot actually simulate this aspect. However, the idea
behind this program was to explore the capability of an observers to count
or estimate correctly storm rates of meteors, and not to explore the
characteristics of meteor perception in individual observers. 

So, lets hope that the Leonids will live up to the high expectations! 

Hartwig Luethen




------- End of Forwarded Message




Follow-Ups: