(meteorobs) Question for the Experts

[Rainer Arlt]

> It did seem to me that my SPO count was rather low.  I
> guess it is likely that I mis-classified a few.
> 
> My question is: Which do you think (or does the
> historic data indicate) is more likely during a PER,
> GEM or similar shower peak - incorrectly identifying a
> SPO as a shower member or a shower member as a SPO? 
> Assume an reasonably knowledgeable observer doing
> their best to be accurate.

This is exactly how the recomended radiant diameters
of meteor shower were determined. According to the
errors of visual observing, an optimum diameter
for which both effect balance is given (see e.g.
end of Shower Calendar at www.imo.net). Of course
this value should depend on the rate the shower produces.
The numbers given there are good for minor showers.
For higher activity, a larger diameter is at optimum.
So for the actual question, I have no number at hand.
Probably more than 20 degrees, although this sounds odd.
But the fraction of sporadics is so small that even if
we counnt all sporadics as shower members, the error is
something like 10%. Assuming a radiant diameter of
10degrees or less, you may end up questioning every
second Perseid's membership, and your error is 50%.
Please note again, that these are not physical radiant
sizes.


Best wishes,
Rainer

-- 
Rainer Arlt  --  Astrophysikalisches Institut Potsdam -- www.aip.de
Visual Commission - International Meteor Organization -- www.imo.net
rarlt at aip.de --  phone: +49-331-7499-354  --  fax: +49-331-7499-526