A minute of arc, arcminute, or minute arc (MOA), is a unit of angular measurement equal to one sixtieth (1⁄60) of one degree (circle⁄21,600), or (π⁄10,800) radians. In turn, a second of arc or arcsecond is one sixtieth (1⁄60) of one minute of arc. Since one degree is defined as one three hundred and sixtieth (1⁄360) of a rotation, one minute of arc is 1⁄21,600 of a rotation. It is used in those fields which require a unit for the expression of small angles, such as astronomy, optometry, ophthalmology, optics, navigation and marksmanship.
The number of square arcminutes in a complete sphere is
or approximately 148,510,660.498 square arcminutes.
The arcsecond is 1⁄3,600 of a degree, or 1⁄1,296,000 of a circle, or (π⁄648,000) radians, which is approximately 1⁄206,265 radian.
To express even smaller angles, standard SI prefixes can be employed; in particular, the milliarcsecond, abbreviated mas, is used in astronomy.
Read more about Minute Of Arc: Symbols and Abbreviations
Famous quotes containing the words minute and/or arc:
“We got a right to climb out of the sewer and live like other people. We could start from scratch. Make every minute count twice for the one we lost.”
—Samuel Fuller (b. 1911)
“If I am not, may God put me there; and if I am, may God so keep me.”
—Joan Of Arc (c.1412–1431)