Posted by: "John Hartog"
> The size of the focal blob will vary depending on the imperfections of
> the dish. Somewhere within this region there will be "points" of best
> focus - that is, one or more small areas where the focus is least
> diffused.
Even if the dish is perfect, it's still considered to be a blob rather
than a point. I'm not sure there are any points as such.
> Though for nature recording, we just move the dish around until we
> find the spot that sounds the best and call it good.
That's pretty much it. The sound sources outdoors are reflected and
absorbed so irregularly that trying to be technically precise just adds
stress level to little purpose. We have plenty to stress out over, like
will there ever be a gap in the aircraft flying over.
Noting how many are surprised to find out that you can adjust the focus
of the Telinga I expect few parabolics are technically at optimum. On
Telinga focus I usually try to focus on something 100-200' away when
adjusting it. But if I want max reach then I may adjust the focus much
more distant.
Walt
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