Hi, I have been trying to rotate an off-axis mirror along the mirror surface axis (Geometric axis of the mirror). 

I have created an off-axis mirror in the sequential mode by decentering. When I tilt the mirror, it only rotate along the vertex of the parabola. 

I also tried to converted to NSC parts. However, it also rotate along the parabola vertex. I tried to created some coordinate to move the mirror to where the geometric center is, but it is quite messy. Is there any better way to do it? 

Thanks a lot.