English: Location of the northern lunistices from 2006 to 2025, in the region of Taurus and Gemini. Each dot shows the location in the sky of the point where the moon reaches its furthest north point during consecutive
tropical months. The first dot, corresponding to mid-September, 2006, is at the top at right ascension 89.0°, and subsequent lunistices are clockwise from there, till the dot corresponding to April, 2025, at right ascension 89.1°. During this 18.6-year cycle, the inclination of the moon's orbit and its node undergo small oscillations, with a period of one eclipse season, or 173 days. This causes the spikes pointing outwards. Each spike occurs when the inclination is maximal, when the sun is lined up with the moon's nodes, and eclipses occur near this moment.
The dates, inclination, and node were calculated using the mean longitude, mean anomaly, mean elongation, mean node, mean argument of latitude, and mean solar anomaly and the periodic terms for the node and inclination given in
"Numerical expressions for precession formulae and mean elements for the Moon and the planets" by the group at the Bureau des Longitudes, Paris, 1994. From the node and inclination, and the obliquity of the earth (assumed constant), one can calculate the location of the lunistice. This is first calculated in the epoch of the date, and then rotated to the J2000 epoch to be put on the graph.