focal length ratio

基本解释

For example, a telescope with a 2032mm focal length and an aperture of 8" (203.2mm) has a focal ratio of 10 (2032/203.2 = 10).
比如，望远镜的焦距为2032mm，孔径为8英寸(203.2mm)，则它的焦比为10 (2032/203.2 = 10)。
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。
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。