The path of the Sun is called the ecliptic in Western astronomysince it is along this path that eclipses occur.

We added a mechanism for the variable motion of the sun and an epicyclic mechanism for calculating the “nodes” of the moon—the points at which the moon’s orbit cuts through the plane of the ecliptic, making an eclipse possible. Eclipses happen only when the sun is close to one of these nodes during a full or new moon. Medieval and renaissance astronomers called a double-ended pointer for the nodes of the moon a “dragon hand.” The epicyclic gearing for this dragon hand also exactly explained a prominent bearing on one of the spokes that had previously appeared to have no function.