File:Length of semester.png

English: Lengths of the intervals between two solar eclipses separated by six synodic months, 2001-2050. The red points are for intervals going from an eclipse at the descending node to an eclipse at the ascending node, and blue points are for intervals going from ascending to descending node. The groups of points linked by green lines represent groups of eight eclipses separated by six months. The scale on the right is the number of hours when the interval is expressed as a number of days plus a number of hours.

Both the red points and the blue points exhibit waves of period 6 years with an amplitude of 19 or 20 hours, peaking when the moon's perigee is 90° from the node. There is also a smaller component of period 18.6 years and amplitude around 8 hours, peaking when the first eclipse is in October and the second one in April. For the red points the high is in 2023-2024 and the low in 2014-2015, and vice versa for the blue.