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Re: (meteorobs) Re: NM past South Delta Aquarid rates


           Kim>>A.   Is is possible to see different but close velocities 
from the
same shower.  For instance, could I designate one leonid as a 5 and another as
a 4?  Would this difference be subjective or due to perspective?<<

Yes it's possible and more than likely. You can easily designate a leonid as 
having an apparent speed of Very Fast(5) and another as simply being Fast(4), 
although the meteors are traveling essentially the same actual velocity. You 
can also end up with other apparent speeds, depending upon where the meteor 
is, in relation to the radiant and also where the radiant itself is located 
in the sky. A lot has to do with perspective and your own "sense" of movement 
for any particular meteor. Speed determination while visual meteor observing 
are not accurate measurements. They are usually not scientifically useful in 
determining a meteors true velocity. They are just a means that helps one to 
make a judgement call along with other criteria for shower association. In 
the scheme of using my meteor scale, two meteors with a sense of speed  at 
scale 5 and the other at scale 4 are both acceptable as being leonids, if 
radiant alignment and acceptable path length in relation to it's distance 
from the radiant and magnitude (if a fireball) are considered. All the while 
being aware of the special circumstances, such as an apparent slowness when a 
meteor appears within about 10 degrees from a radiant. For showers with Very 
Fast velocities, accepting meteors at scale 5 and scale 4  takes into account 
of being off some in your judgement calls for apparent speeds while not 
eliminating shower members because of a person's slight impression difference 
of speed from time to time.


       kim>>    B.  When meteors have extremely short path lengths, I find it 
quite
difficult to give many of them what I feel would be accurate velocity ratings.
Should I take Lew's advice and just "call 'em as I see 'em" (as best I can)?<<

Meteors with very short path lengths near a radiant, fall into the special 
circumstances category. When you see one, the other shower determination 
criterias come into more importance. You are essentially using a form of 
"Kentucky Windage". If you are just using the Counting method of recording 
your data, recording speed on any kind of scale serves no real purpose. 
Nobody later is gonna have anything to refer it to check up on you. You are 
only noting speed for a short moment along with a couple other things to make 
a judgement call for shower association. Now if you were plotting, noting a 
speed scale of some kind can become useful for someone later looking at your 
data. Yes take lew's advice and just call em as you see them. You will make 
mistakes, this is an understanded given. When dealing with a major shower, 
you will probably be seeing enough meteors for a few errors to not change 
anything significant in the final analysis. 
GeoZay
                      
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