focal ratio [光] 焦比 ; 焦距比 ; 焦度
nominal focal ratio 标称焦比 ; 标称焦距比
Focal Length Ratio 焦距变换比率 ; 焦距比 ; 焦距换算倍率
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。
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203.2 x 10 = 2032mm。
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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