Greetings fellow dialists, You don't have to have a clear sky on the actual day you are wishing to mark sunrise or sunset. Martin Brennan in his book "The Stones of Time" showed elegantly how the people at Newgrange in Ireland did it five thousand years ago with the rising solsticial sun shining down a long shaft into the immense earthwork onto auxiliary marks for adjacent days.
More recently there is a simple noon line in Durham Cathedral dated 1829 with extra marks for five and ten minutes after noon. This line was simply a clock regulator, though. Frank, 55N 1W -- Frank Evans
