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Re: (meteorobs) Meteor lengths (was Re: Meteor lenghts)
Jure, you've never asked a stupid question yet... (In fact, other than one or
two "experts" who have since left our list, I don't know of anyone who has!)
The answer is that there *is* no "right length" for a meteor to be, in order
for it to be assigned to a particular shower... And even the "wrong length"
maximum which the IMO Handbook suggests (one half the angular distance from
the radiant to the meteor starting-point) is *only* a rule of thumb...
As you indicate, in cases where the meteor is less than 10 degrees from the
radiant, or is a fireball which may happen to penetrate deeper into Earth's
atmosphere before "burn-up", the "maximum length" rule may not even apply!
However, the IMO "half-the-radiant-distance" rule is still very valuable for
meteor observers, even though it's only a limited approximation: without it,
we observers would misidentify many more Sporadic meteors as being from the
minor showers we watch for - and our data would be correspondingly worse!
(For the detailed calculations on which the "half-the-radiant-distance" rule
is based, and also for quantitative estimates as to how much this criterion
reduces "Sporadic pollution" in minor shower rates, see the IMO's Handbook.)
Clear skies,
Lew
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