Minute and second of arc
| Arcminute | |
|---|---|
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.
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| 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° ≈ 0.0167° |
| arcseconds | 60′′ |
| radians | ≈ 0.2908/1000 rad |
| milliradians | ≈ 0.2908 mil |
| gons | 600/9g ≈ 66.67g |
| 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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