Determine the X and Y coordinates of a star on the TV acquisition screen. Change the Sky Position Angle (SPA) by 180 degrees. The star describes a semi-circle reaching a final location on the TV (i.e., [Xf,Yf]). The center of this circle [(X+Xf)/2,(Y+Yf)/2] should be the rotator center. Repeating this process will lead to a more accurate determination of the rotator centre.
To minimize tracking uncertainties, select a star near the pole.
After the rotator centre has been determined a CALIBRATE should be done at this point.