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The f-ratio is the focal length divided by the
diameter of the telescope. Magnification is the
focal length of the telescope divided by the focal length of
To find the f-ratio of a telescope 10 " in diameter with
a 45" focal length:
- Divide 45 " F.L. by10" D. to get an f-ratio of
To compute magnification:
First, convert focal length to mm: 45" = 1146 mm, then:
- 1146 mm focal length divided by 35 mm eyepiece equals 33