Richard Jarnagin wrote:
It is my understanding that the area of the objective primarily determines
the *amount* of light collected by a given instrument. You do not have
"more light" or "less light" available due to strictly a difference in focal
ratio, unless you want to take into account the effects of increased
scattering along the longer focal length of the higher focal ratio scope.
Understand that I am not questioning your assertion of the dependency of
image intensity upon focal ratio, only your implication of the dependency of
the amount of available light (i.e. "more light" "less light").

Right--I was unclear. I do mean a higher (or lower) collected light
to image area ratio, which essentially reduces to image intensity.

I'm sure the increased scattering due to a longer focal length is
quite negligible. What would be there to scatter the light, aside
from the air?

Brian Tung
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