The Lunar Nodes
The two points where the Moon’s orbit crosses the ecliptic — the Sun’s apparent path. The ascending (North) node and descending (South) node drift slowly backward through the zodiac, and eclipses can happen only when a New or Full Moon falls near one of them.
North and South
The Moon’s orbit is tilted about five degrees to the ecliptic, so it crosses that plane at two opposite points. Where the Moon rises above the ecliptic is the ascending or North node; where it drops below is the descending or South node.
The nodal cycle
The nodes do not stay still: they move backward through the zodiac, completing a full circuit in about 18.6 years. In Indian astrology the two points are named Rahu and Ketu and treated as shadow planets.
Why they bring eclipses
An eclipse needs the Sun, Earth and Moon in a line, which happens only near a node — which is why eclipses arrive in seasons rather than every month, and why they repeat on the long Saros cycle.
Connections
- The Synodic Month — The average time from one New Moon to the next — about 29.53 days. It is the cycle of the Moon’s phases as seen from Earth, and the ‘month’ at the root of lunar and lunisolar calendars.
- The Void of Course Moon — The stretch of time when the Moon, having made its last major aspect in a sign, will make no more before it moves into the next. It is traditionally read as a pause — a time to rest and reflect rather than to begin something new.