This would be the stuff from that, that you are interested in.

function moveMoon()
{
//convert the angle value to a radian value
var _loc1 = deg2rad(moon_mc.ang);
//caclulate the x coordinate along the arc
moon_mc._x = moon_mc.xc + moon_mc.rad * Math.cos(_loc1);
//caclulate the xycoordinate along the arc
moon_mc._y = moon_mc.yc + moon_mc.rad * Math.sin(_loc1);
//update the angle variable using the incriment value for the next raound of calculations
moon_mc.ang = moon_mc.ang + moon_mc.angC;
//ensure that the angle variable stayes below 360.
moon_mc.ang = moon_mc.ang % 360;

//if the angle value of the clock has reached 0 or the 3 o clock positon along the arc, reset the position to llook like it is comming out of the horizon near the 9 o clock positon
if (moon_mc.ang == 0)
{
moon_mc.ang = 175;
} // end if
trace (moon_mc.ang);
} // End of the function
//utilitly function for converting degree value to a radian value
function deg2rad(degree)
{
return (degree * 1.745329E-002);
} // End of the function
//calculate a center point for which the arc will be calculated arround. This is the pivot point from which the distance and degree cacluation will stem from.
moon_mc.xc = Stage.width / 2;
moon_mc.yc = Stage.height;

//radius, the distance from the calculated center point that the object should arc arround.
moon_mc.rad = 400;
//inital value for the angle. This determines starting location along the arc.
moon_mc.ang = 225;
//angle incriment value. This value gets added to the angle value on each update moving the object along the path. The higher the value the more it moves on each update.
moon_mc.angC = 1;
moveMoon();
var orbit = setInterval(moveMoon, 8000);