Comparison of the drawings by Scheiner (left) and Harriot (right) on the two days they have common observations. The top row shows the observations of 1611 December 11, at 14 h (left) and at 10 h (right). The bottom row is of 1611 December 13, at 13 h (left) and at 8:30 h (right). The vertical dashed lines in Harriot’s drawings denote the (observed) direction to the zenith, the other dashed lines are the (computed) ecliptic.