1 Arcminute:1 Arcminute (Minute of Arc - MOA) is equal to exatly one 60th of a degree. In terms of the SI unit radians this is π/10800 or approximately 0.290 888 x 10-3 rad.
Circle:A circle is a simple closed shape. It is the set of all points in a plane that are at a given distance from a given point, the centre; equivalently it is the curve traced out by a point that moves so that its distance from a given point is constant. The distance between any of the points and the centre is called the radius.