I would do it with sine-wave, because it makes smooth moves.

Hope these bits help, its not ready code so you would have to adapt it:
Code:
const ToRad = 0.0174532925199433;  //  PI / 180 = Deg To Rad
...
Counter:=(Counter+1) mod 360;
Moon.AnimPos:=72+72*sin(Counter*ToRad);