Hi Ruby, wellcome
Get the Sun's Azimuths from the South (Z), Z=arctg(senH/(senL*cosH - cosL*tgD)) where H hour angles L latitude D Sun'declinations the seven D angles are 0, 11.475, 20.155, 23.443, -11.475, -20.443 and -23.443 The shadow points on the hour lines (H) are away from the Radiant Point the distances P P = VG*senZ / (tgL*sen(Z - arctg(senL*tgH))) where VG height of the vertical gnomon jorge Portugal N 38 47 W009 19
