Assertion: telescope's ratio | /r/HasProperty | f/number
Facets:
Source sentences:
text: The focal length is equal to the telescope’s focal ratio (f/number) multiplied by the diameter of the primary optic, or aperture.
text: If you have the telescope's focal ratio (f/number) you can measure the diameter of its primary optic - either the large mirror for a reflector telescope, or the large lens of a refractor telescope.
text: If you have the telescope's focal ratio (f/number) you can measure the diameter of its primary optic - either the large mirror for a reflector telescope, or the large lens of a refractor telescope.