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Field of View



-- [ From: Robert Lunsford * EMC.Ver #2.10P ] --

Mr. Gramer,

Mark Davis forwarded these questions to me from the new mailer. I hope
you find my answers satisfactory. Also, please add my name to the
mailer and perhaps I can answer some future questions firsthand.

Thanks,   Bob Lunsford

The question regarding field of view is being made more complicated
than it needs to be. Your field of view is obviously all the sky within
your eyes limit. This includes the moon, moonlight, horizon, or
anything else you can see. Although the moon is in the sky but out of
your FOV it will reduce your limiting magnitude just as skyglow from a
city. You are not looking at the city, but the skyglow still
interferes. Both of these cases would be indirect interference which
does not affect the FOV, but rather how dark the FOV will be. Different
observers have different sized FOV's. Some people see meteors well near
the edge of their field while others suffer from "tunnel vision".
Obviously, the observer with "tunnel vision" will see less activity
than someone with activity over their entire FOV.

 Now if that bolide occurs behind your FOV, you would still report it
to the best of your ability. You simply cannot ignore the bolide
because it occurred out of your FOV. Bolide reports are important
whether you saw the actual meteor or just the remaining train. You
would also note in your report that you saw the flash and not the
actual meteor. This would make it perfectly clear to anyone reading
your report that the bolide occurred outside your FOV.

Mark is perfectly correct in stating that your hand shielding the moon
should be noted as an obscured portion of the sky.

With regard to FOV verses meteor magnitudes, certainly no one sees
faint meteors at the edge of their FOV. Should we create different
FOV's for each magnitude? I feel this is carrying the situation a bit
too far. It is a fact that observers see faint  meteors only near the
center of their FOV's and that brighter ones may be seen all the way to
the edge. Let us leave it at that and simply concentrate on reporting
the center of view for each hour (as it now appears on all updated
visual observing forms)
and not worry about the size of one's FOV.  Sizes of one's FOV would
fall under an entirely different catagory called perception. 

Bob Lunsford