In this paper, we solve the problems of output-feedback semiglobal stabilization and tracking for the nonlinear benchmark RTAC example when the angle of the proof mass and/or the translational position of the cart are considered as the output. The proposed results complement previous work which requires exact knowledge of the translational and/or angular velocities but achieves global stabilization or global tracking. As is demonstrated in simulations, the output-feedback stabilizing and tracking controllers proposed in this paper yield performance as good as their counterparts with state feedback.