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Re: (meteorobs) Re: Angular velocities
I've had too many emails today to have read them in any detail, so I hope
my comments don't cover things already said. The eye/brain directly
perceives angular velocity, whereas path length and duration must be
derived after the event and neither is directly perceived. One requires
memory of what the various scales (or absolute calibration) is, the other
requires memory of how long one second is, unless some audible time signal
is used. It must also be borne in mind that the angular velocity is
constantly changing and Pete Gural has discussed this a few months back.
Whatever method is used, it is important that the estimates be accurately
calibrated against the theoretically derived angular velocity (from the
overall geometry of each meteor using an assumed height which will likely
introduce a very small error) or by comparison with the measured angular
velocity by video or photography. Comparisons between observers may
represent the overall scatter but don't necessarily exclude the
possibility of an overall systematic error (internal scatter by
intercomparison of estimates is always smaller than the scatter of the
absolute errors).
One final point. Do observers compensate for zenithal attraction in the
radiant in assigning a meteor to a radiant?
Cheers, Rob
Robert H. McNaught
rmn@aaocbn.aaodot gov.au
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