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.
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Famous quotes containing the words minute of, minute and/or arc:
“I make this in a warring absence when
Each ancient, stone-necked minute of loves season
Harbours my anchored tongue....”
—Dylan Thomas (19141953)
“Well, theres no one at all, they do be saying, but is deserving of some punishment from the very minute of his birth.”
—Augusta, Lady Gregory (18591932)
“You say that you are my judge; I do not know if you are; but take good heed not to judge me ill, because you would put yourself in great peril.”
—Joan Of Arc (c.14121431)