Assertion: focal ratio | /r/HasProperty | f/number
Facets:
value: often
type: TEMPORAL
Source sentences:
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: The Focal Ratio (f number) is the Focal Length divided by the Objective Diameter.
text: The focal length divided by the aperture is the focal ratio (the f/ number).
text: The focal ratio is often called the f-number.
text: Focal ratio (f/number)
text: Focal Ratio (f/number)