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:

“I did the dragon’s will until you came

Because I had fancied love a casual

Improvisation, or a settled game

That followed if I let the kerchief fall:

Those deeds were best that gave the *minute* wings

And heavenly music if they gave it wit.”

—William Butler Yeats (1865–1939)

“Male urination really is a kind of accomplishment, an *arc* of transcendance. A woman merely waters the ground she stands on.”

—Camille Paglia (b. 1947)