On the vernal and autumnal equinoxes the higher stone casts its shadow over a stone approximately 11m away.
The gradient of the top of the stone is in good alignment with the sun’s path.
Notice that the shadows movement across the stone is exactly correct on the day before the vernal equinox and the day after the autumnal equinox (“refraction equinox”). It is on these days that day and night are of equal length.
In 2014 this will take place September 24th between 06:55 and 07:03, that is to say a period of around 8 minutes. During the autumn the leaves of a birch tree completely obscure the sun. This prevents the possibility of viewing the sun shadow on the autumn equinox. On the spring equinox there are no leaves on the tree and the shadow may be clearly seen.