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Re: (meteorobs) Another failed Observing Session
In a message dated 98-05-22 12:35:25 EDT, you write:
Kevtk<
Why are some showers removed from the observing lists?
>>
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Some are removed because their ZHR's are very low...less than 3 ZHR at best.
Trying to record their activities by means of visual observing wouldn't be
productive because they wouldn't stand out beyond the normal background
sporadic activity. The only meteors that I think would be exceptions are those
that have exceptionally slow velocities such as the Tau Herculids. These would
have velocities on the scale of being 1...which is Very Slow. I seldom ever
see meteors of this velocity. The normal slow meteor that I notice in the
evenings would be a 2. A meteor with a velocity scale of 1 would stand out so
much that even with a ZHR less than 3 it would be readily recognizable.
Other meteor showers are removed because of the lack of a reliable history of
any activity. Some might have been nothing but One Shot Wonders. As for the
IMO list, it reflects showers that are readily recognized as an Active list
that visual observers can contribute some worthwhile observations on. There
probably are some other genuine very weak showers, but keeping track on their
activity isn't reliable enough to be done by visual means. Some other
showers removed were also redundants of another shower under a different name.
These were consolidated into one. One of the purposes of IMO is to clean up a
large list of shower names of the past, and concentrate only on those that
aren't obscured as to being real or not. I'm sure if plottings from a number
of observers indicate a shower is present, they will eventually be added to
the working list.
George Zay