I jsut did a little experiment with my phone camera.
My camera has gridlines.
So what I did is set up a an object ball and use either the right or left grid line to line up center CB with the edge of the ob. Then I pivoted the camera so that center CB was right in the center of the frame. THEN I had my assistant place the Ghost Ball to see if the GB would then be in the center of the frame as well.
And........ it was!
HmmMmmmmmmm ok