Rotation in the inner and outer regions of NGC 1851. The plotted value is the average radial velocity of stars in a 180 degree sector, minus the average velocity of the whole cluster. The half cluster sector has been moved by 10 degrees from one point to the next. The maximum rotational velocity in km s^-1 is derived from the best sinusoidal fit of the data. The position angle (in degrees from North toward East) of the rotation axis is also shown.