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Re: (meteorobs) Re: FOV of Field definition
This topic of where to put your Center of Field of View (CFV) relative to a
shower radiant, is one we've been through a couple of times before - as with
most meteor-related topics, probably, after 4 years and 20,000 emails. :>
Bob Lunsford is of the opinion that facing the radiant maximizes perception
and (he has recently mentioned) may enhance an observer's ability to do path
shower association while observing. One reason for improved perception that
I have heard in the past is the fact that shower meteors will appear slower
(and maybe somewhat brighter on average?) near the radiant, due to the for-
shortened appearance of these more "head on" meteors.
I wasn't sure I had understood your point about easier shower association,
Bob? Is it because watchers will be better able to "triangulate" on the
radiant point, since they'll get to see meteors trace back to the radiant
from "360 degrees around"? Maybe you can explain that one in more detail?
In any case, many observers share Bob's point of view. (Pun intended!)
Mark Davis writes in the NAMN Observing Guide, and many observers (like me)
agree with him that facing 30-40 degrees away from the radiant will actually
improve perception, as shower meteors will appear longer on average, making
it easier for the eye to detect them. This is especially true for observers
with narrower fields of meteor perception (say average DCVs of 20o or less).
Also (I would propose), shower associations will be no less accurate, and
possibly more so. This is because meteors of longer paths will show up the
distinctive angular velocities of a particular shower better, relative to
the sporadic background. Also, the path *length* criterion is much easier
to apply to a meteor, if it is seen more than 20 degrees from the radiant.
And of course, if you are watching MULTIPLE radiants, then having a leeway
of 30-40 degrees may allow you to choose your CFV in such a way as to view
more than one of those radiants to advantage at the same time.
So naturally, many observers agree with Mark's view, as well!
And of course, neither of these two views may be correct for everyone: in
the past, for example, I have suggested to Bob that his meteor perception
may actually be different from mine, in that he may be most apt to notice
any *brightening* in the sky, whereas I'm more apt to pick up *motion*.
So the final answer seems to be, "Choose whichever CFV is most comfortable,
so long as you can see the radiant points of all the showers you're logging,
well enough to do accurate shower associations". And of course, be sure to
log your CFV carefully. Then maybe some day, someone can actually analyze
the global meteor database to find a better answer to this very question! :)
Clear skies!
Lew Gramer
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