Numerical Aperture and F-Number - Eckhardt Optics - Equating to f/#
Telescope stats explained - BBC Sky at Night Magazine
An astronomical telescope has an objective of focal length 200 cm and an eye piece of focal length 10 cm. An observer adjusts the distance of the eye piece from the objective
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How to Calculate the Field of View of Your Telescope - StarLust
What determines a telescope's fstop? I often see the same size lens with different fstops. - Quora