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(meteorobs) Zenethal Attraction



Again zenithal attraction:

>If you place your center of field between 50 and 70 degrees 
> in altitude (as the IMO recommends) then the Z. A. would 
> be close to zero and would not be a factor in your data.

This is not true. Zenithal attraction affects all meteoroids before
entering the atmosphere. The meteor can't know the observer. If you observe
a zenithally attracted shower, you'll find that all the paths belonging to
this shower converge at a radiant shifted against the unattracted position,
in whatever direction you were looking. A meteor at 50deg elevation, at
90deg azimuthal elongation from the radiant will be significantly affected,
since its orientation is changed. To make it clear: It is not the zenith
distance of the meteor which is changed. Anyway, in most cases the effect
is negligible for visual shower association.

Rainer Arlt

---------------------------------
Visual Commission
International Meteor Organization
email:  visual@imodot net
Homepage:  http://www.imodot net
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