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I guess it gets confusing when the FOV changes all the time, generally when you change aperture the FL generally changes too.
However in this is perhaps a good example?
an 8" f5 newt (FL 1000mm) vs a 10" f4 newt (FL 1000mm) same field of view an extra 2" light gathering power hitting the sensor in the same spot, makes sense the 10" (or f4) is "quicker".
Russ
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