Since the reflected points emanate from the (curved) scratches themselves, I would think that between the left and right eyes, each point would be slightly vertically misaligned (since each eye would see light from a different <i>vertical</i> point in each scratch, beside a different <i>horizontal</i> point).<p>I suppose you could eliminate this by drawing the scratches as if they were cross-sections of a Fresnel lens: i.e., at several points during the scratch, reposition the compass fulcrum vertically so that the needle remains at approximately the same vertical location.