Quote:
Originally Posted by RobF
Paul (1Ponders) also educated me that the light gathering capacity is related to the square of the focal length. That is, if you had say an F6 80mm refractor, and an F9 80mm, the F9 would take about 81mins to gather what the F6 could do in 36mins.
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Hi Rob,
I think you probably meant to write “the square of the focal
ratio” and not “the square of the focal
length”?
Cheers
Dennis