The stones show the point on the horizon where the sun rises at the spring and autumn equinox. The distance between the stones is 13 m.
The gradients of the top of the stones are in good alignment with the sun’s path. Notice that the sun’s path is exactly right the day before the spring equinox and the day after the autumnal equinox (“refraction equinox”). It is these days that day and night are of equal length.
Forest obscures the sun at sun rise.