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(meteorobs) no messages ? and perception
-- [ From: Robert Lunsford * EMC.Ver #2.5.3 ] --
> Is it just me or is nobody receiving messages, I've re-subscribed in
case if
> been taken off by accident
>
Thanks to Lew for explaining this situation.
> One question to you all though, observers perception, I don't have
alot of info
> on it and I was wondering the best way to work it out for observers in
our
> group.
>
I would not advise including perception figures in with your data.
Perception figures are only used in the global analysis of major showers
. After gathering sufficient data the IMO is able to compute a
perception coefficient for each observer based on observed rates and
observing conditions. Using global results and analysis an observer
should be seeing a certain number of meteors. Any deviations form this
figure results in a better or worse perception figure. If you are seeing
only 50% of the meteors under standard conditions that you should be
seeing then your rates need to be doubled (2.00) in order to fit the
activity profile. I have not seen a list published during the last 5
years but I recall the last time a list was published that I was very
close to 1.00 meaning that I was an "average observer". An observer with
a PC less than 1.00 would have better than average perception and their
rates would have to be reduced in order to fit the activity profile.
I can see where you would be curious about the perception of everyone in
your group. You can figure it for each observer by correcting each
observers totals for time and limiting magnitude and then the resulting
totals will reflect perception. For example observer #1 with a LM of 6.0
saw 50 meteors in 3 hours: Correcting 6.0 to 6.5 (the standard LM) = 50
(# of meteors seen) X 1.73 (correction factor) = 86.5 Observer #2 saw
100 meteors in 3 hours at the exact same time and location with a
limiting magnitude of 7.0. Correcting 7.0 to 6.5 = 100 X 0.58 = 58
If both of these observers observers had an LM of 6.5 #1 would have seen
86 meteors while #2 would have seen only 58. Observer #1 has the better
perception (1.49 times better than #2). The average of the two would be
72. The correction figures are taken from the table on page 47 of the
1989 version of the IMO Handbook. An "r" of 3.0 (the average sporadic
meteor) was used.
You may not believe it is possible that people observing together can
differ in LM by one whole magnitude but George Zay and I have done it on
several occasions. It does not mean that one of us has poor eyesight,
especially when the observer seeing less meteors could have the better
perception (as shown in the example above).
I would advise limiting perception calculations to active nights during
major showers. Low counts may yield inaccurate results.
I hope this helps and does not add to anyones confusion. Many of the
factors above are oversimplified.
I have reread this many times and even I'm not certain if it makes 100%
sense, but it is my humble attempt to clarify this subject.
Bob Lunsford
IMO/ALPO