Editing Binoculars (section)

=== Range finding ===

Some binoculars have a range finding [[reticle]] (scale) superimposed upon the view. This scale allows the distance to the object to be estimated if the object's height is known (or estimable). The common mariner 7×50 binoculars have these scales with the angle between marks equal to 5&nbsp;[[angular mil|mil]].<ref name="bushnell">{{Cite web |url=http://www.binoculars.com/images/pdf/BUP336.pdf |title=Binoculars.com — Marine 7 × 50 Binoculars. Bushnell |access-date=2009-07-05 |archive-date=2011-09-10 |archive-url=https://web.archive.org/web/20110910153501/http://www.binoculars.com/images/pdf/BUP336.pdf |url-status=live }}</ref> One mil is equivalent to the angle between the top and bottom of an object one meter in height at a distance of 1000 meters.

Therefore, to estimate the distance to an object that is a known height the formula is:

:<math>D = \frac{OH}{\text{Mil}}\times 1000</math>
where:
* <math>D</math> is the ''Distance'' to the object in meters.
* <math>OH</math> is the known ''Object Height''.
* <math>\text{Mil}</math> is the angular height of the object in number of ''Mil''.

With the typical 5 mil scale (each mark is 5 mil), a lighthouse that is 3 marks high and known to be 120 meters tall is 8000 meters distant.

:<math>8000 \text{m} = \frac{120 \text{m}}{15 \text{mil}} \times 1000</math>