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 $\pi /10,800 radians$. 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. the milliarcsecond, abbreviated mas, is used in astronomy.
Milliarcsecond