For example, the focal length of an 8" (203.2mm) aperture with a focal ratio of f/10 would be 203.2 x 10 = 2032mm.

比如，孔径为8英寸(203.2mm)，焦比为f/10的透镜，其焦距为203.2x 10 = 2032mm。

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Or, you can calculate the exit pupil by dividing the focal length of the eyepiece (in mm) by the focal ratio of the telescope.

或者，你还可以将目镜的焦距除以望远镜的焦比来得到出瞳尺寸。

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This is the ratio of the focal length of the telescope to its aperture.

这是指望远镜的焦距与其孔径的比值。

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If you know the focal ratio but not the focal length, you can calculate it: focal length is the aperture (in mm) times the focal ratio.

如果你不知道焦距，只知道焦比(focal ratio)，你可以通过这样计算的得到焦距：孔径(单位是mm)乘以焦比就是焦距。

youdao

If you know the focal ratio but not the focal length, you can calculate it: focal length is the aperture (in mm) times the focal ratio.

如果你不知道焦距，只知道焦比(focal ratio)，你可以通过这样计算的得到焦距：孔径(单位是mm)乘以焦比就是焦距。

youdao