The Stonehenge Solstitial Alignments

At Stonehenge the difference between the Solstice Sunrise and Sunset alignments is 81 degrees, the exact angle between a line drawn between the 42nd and 15th minute mark on a clock face, compared to the 0 to 30 line. It is built into the stones with the outer sarsen ring, and the Altar Stone and middle Trilithon.