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Radiants, was Re: (meteorobs) A blank meteor reporting form



>Knowing which criteria an observer chose to use that night might be
>very important in calibrating their result later. Or am I off here?


Hi Lew,

No, I think you are correct Lew. I believe where the confusion may lie is in
that the radiant diameter on the NAMN form is asking for the *assumed*
radiant size, not an actual or theoretical one. It is true radiant diameters
are of the most value to those plotting meteors, but even observers making
visual counts have to assume a rough radiant diameter (what many may call
the location) or else meteors will be misclassified.

The radiant diameters that NAMN uses are those in the IMO Handbook. It is my
understanding that proposing a diameter for the Orionids of 10 degrees let's
say, was done as this was the optimal diameter with regard to plotting
errors, sporadics, etc. I have not seen any adjustments made to this by IMO,
but maybe an IMO officer on the list can advise me if I missed it somewhere?
If I did miss the change, than we will probably finish the year out with the
old diameters, and start fresh on January 1st.

My suspicion though, is that assuming a radiant diameter of 0.84 for the
Orionids, or 0.32 for the Leonids, or similar diameters for other showers,
will result in even more meteors being misclassified, especially as you move
further and further from the radiant.

Mark Davis, South Carolina
NAMN Coordinator