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Re: Meteor Velocities



Bob,

I feel the NAMN scale is accurate enough to determine shower memberships for
radiants of even low altitude.  After all, the purpose is to enable an
individual to make judgement calls for shower associations, you aren't really
measuring anything.  I highly doubt any more classification errors would
occur with the NAMN scale as the deg/s method.  Estimating in degrees/sec
would probably give you more accurate velocities, but we aren't looking for a
value that is accurate...just a means to quickly determine shower membership.
 If you wanted to get accurate to go beyond shower determinations, you need a
camera system of some sort with rotating shutters or some other electronic
means that goes beyond the human senses. All either method is good for is
making a determination of what shower a meteor belongs to.  If this could be
done satisfactorily, why the bother to get velocities to the nitty grittieth
power if that isn't good enough for anything else? 
As for meteors lasting 15 seconds.  Well, I haven't seen one either.  As a
matter of fact, I've only seen about a dozen or so meteors that I would group
in scale 1.  I seldom have to use it. And the one's I have seen didn't go
very far.  But if there was one moving at that rate and went across the sky
as the Alpha Aurigids we were referring to, I'm sure it could take 15 seconds
or more.  Scale 0 is stationary.  Scale 1 is moving but very slow. Scale 2 is
the typical slow meteors that I normally see and 3 is of medium rate.  Scale
4 is fairly fast but still able to see the meteors head and 5 is nothing but
a streak with no perception of a meteors head.  1 is on the extreme end of
the scale.  It exists to make room for that seldom possibility.  It doesn't
mean the meteor will last for 15 seconds, but if it crossed the sky, that's
how it will appear. 

When you estimate in degrees/sec, you are making two estimates.  You're
estimating time and distance.  Whereas with the NAMN scale you are only
estimating apparent time.  It would seem to me that the more separate
estimates made for a factor, the more inaccurate it's final value will be.  I
know some very experienced observers are quite good at estimating deg/s and
that's great! But why shoot gnats with an elephant gun when a pea shooter is
just as deadly? In this case, making deg/sec estimates is overkill for
something that can be accomplished in a more simpler manner.  Now if there
were a genuine need for visual deg/sec data beyond shower determinations,
then I can see the advantage.  But I haven't come across anything that would
dictate deg/sec over the NAMN scale.  At best they are equal, and I
personally feel that the scale is superior for it's intended purpose. 

Whether estimating durations in 1/5th or 1/10th of a second is within the
scope of reality or not is not really an issue here. The question is whether
it's worth having to think in tenths or fifths of a second while your mind is
needed to note magnitudes, alignments, trains, times etc. I note all these
too, but if I can eliminate having to think about one more factor and still
accomplish the same resultant goal if I did, why put yourself thru it?

Bob was right when he said it's important to not make observing a chore.  But
wouldn't doing more steps than necessary constitute a chore?  Albeit a rather
small chore but multiplied with the number of meteors seen.  When you
consider fatigue of any degree a factor (and no matter how alert you feel,
some fatigue will exist simply because it's not natural for one to stay awake
during the wee hours), unnecessary steps becomes bothersome whether it's
conscious or not.
George Zay