The rather clever thing about having a 3 dimensional 'hole' with a varigated diameter profile as well as a non-linear depth, is that it becomes possible to work out very accurate positions using the extinction angle whereby you can no longer see the Sun through it. Once you have this capability, all you need is an equally accurate time marker and you can then work on producing an analemmic curve of the sun's apparent path and therefore work out that the planet is kind of spherical and wobbles as it spins. The combination of the capstone aperture and noon notch may have enabled such observations!
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