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(meteorobs) RE: Meteor length question
Kevin,
The meteor length is proportional to sin(distance from radiant) AND proportional
to sin(elevation). If meteor and radiant are higher than say 30 deg in the sky,
the rule that the meteor should not be longer than half the distance to its
radiant, is valid. Meteors near the horizon should be even shorter. On the other
hand, if the radiant is close to the horizon, meteors can be as long as the
distance from the radiant. The mathematical approximation is
length=arcsin [ DeltaH sin(distance) * sin(height) / ( H*sin(radiant height) )
]
H is the average meteor elevation in the atmosphere (~100km). DeltaH is the
difference between beginning and end height (~10-20km). (Earth curvature not
taken into account, hence infinity for radiant height=0deg.)
If the meteor you describe is rather long, say as long as meteors higher in the
sky, it has its radiant rather far away, so I would favour the NTA radiant. If
it was particularly short it is a STA. Discriminating such close radiants is
most difficult. I suggest to choose observing fields east or west of the
radiants, keeping the number of ambiguous meteors small.
Rainer