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Re: Radiants, was Re: (meteorobs) A blank meteor reporting form
Mark>>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. <<
Oh? This is the first that I've heard that the radiant diameters asked for
were assumed diameters? Can you please explain how different assumed
diameters has been selected for different showers of relatively the same small
size? Such as the "assumed" diameters of the Orionids being 10 degrees and
Leonids being 5 degrees? I'm really curious how NAMN can explain these
designators?
I noticed on the IMO visual recording forms in the IMO Handbook for Visual
Observers no longer has a place to enter radiant diameters. Perhaps NAMN
hasn't caught up with the IMO form?
Mark>>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.<<
Yes, this is not what is in dispute. Why have one shower starting off with one
diameter and another a different diameter?
Mark>>The radiant diameters that NAMN uses are those in the IMO Handbook. <<
Oh...where? Which radiant diameter do you start with...the one where the
meteor is 15 degrees from the center of the radiant? This would be 14 degrees
then. What if there were no meteors, how big is the diameter you would use on
your form? The varying shower diameters as the meteor is further from the
radiant is not in dispute. But in IMO's handbook for visual observers, I can't
find where it is referenced to have the varying diameters of different showers
from the get go. Table 8-3 and Table 8-4 don't list the disputed radiant
diameters that can be found in IMO's Shower Calendar.
Mark>>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?<<
Why 10 degrees for the Orionids? How can 10 degrees be more optimal for the
Orionids and 5 degrees be more optimal for the Leonids? They both have very
fast meteors. If anything, make them both 10 degrees or 5 degrees? I've seen
the adjustments in IMO's handbook for visual observers...they are no longer
listed both in the book and on their newer forms in the back of the book. I
believe they are listed in the IMO calendar as an oversight? They are no
longer listed in the tabular tables of IMO's working list like they use to.
Mark>>If I did miss the change, than we will probably finish the year out with
the
old diameters, and start fresh on January 1st.<<
This is where I came in and suggested that you remove the radiant diameter off
your form.
Mark>>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.<<
Comparing apples with oranges here mark. You still keep the radiants at their
actual sizes if you must have them at all on your form. There is no point in
having them at all actually. But in classifying meteors by showers, you still
adjust the radiant area for acceptability as the meteor appears further from
the radiant...as suggested in IMO's handbook in tables 8-3 and 8-4.
George Zay