A line connecting the two points of the Moon's Perigee and Apogee, the longest axis of the Ellipse of the Moon's orbit. A Progression of this line causes the Moon's orbit to turn on itself once every 3232.5 days, about 9 years. This produces the Apse Cycle. It can also be defined as a line which connects the perigee and apogee of a body'sorbit, or any eliptical shape in general.
Comments: Apsides line