This is the second half of the setup for the transit check: Red tape marker stuck on the window pane representing the "distant object".

The crucial detail is that the "near" and the "distant" objects must be placed exactly along a line intersecting the pivot of the turntable. This takes a considerable amount of time - it must be done very carefully and precisely whilst at the same time ensuring that the camera will see the "distant" marker ATOP the "near" marker.