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Arc-second

Arcminute
Arcminute and football.png
An illustration of the size of an arcminute. A standard association football ball (22 cm diameter) subtends an angle of 1 arcminute at a distance of approximately 775 meters.
Unit information
Unit system Non-SI units mentioned in the SI
Unit of Angle
Symbol  or arcmin 
In units Dimensionless with an arc length of approx. ≈ 0.2908/1000 of the radius, i.e. 0.2908 mm/m
Unit conversions
1 in ... ... is equal to ...
   degrees    1/60° = 0.016°
   arcseconds    60′′
   radians    π/10800 ≈ 0.000290888 rad
   milliradians    ≈ 0.2908 mil
   gons    600/9g = 66.6g
   turns    1/21600

A minute of arc, arcminute (arcmin), arc minute, or minute arc is a unit of angular measurement equal to 1/60 of one degree. Since one degree is 1/360 of a turn (or complete rotation), one minute of arc is 1/21600 of a turn (or, in radians, π/10800). A second of arc, arcsecond (arcsec), or arc second is 1/60 of an arcminute, 1/3600 of a degree, 1/1296000 of a turn, and π/648000 (about 1/206265) of a radian. These units originated in Babylonian astronomy as sexagesimal subdivisions of the degree; they are used in fields that involve very small angles, such as astronomy, optometry, ophthalmology, optics, navigation, land surveying and marksmanship.


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Wikipedia

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