Lunar Nodes (True vs. Mean)
The lunar nodes are the two points where the Moon’s orbital path intersects the ecliptic—the Sun’s apparent path. The ascending (north) node is where the Moon crosses into the northern ecliptic hemisphere; the descending (south) node is the opposite crossing. These nodes are essential to eclipse timing: eclipses occur only when a new or full Moon is close to a node.
Astronomy & timing
- Why nodes matter: the Moon’s orbit is tilted ~5° to the ecliptic; alignments at (or near) nodes enable lunar/solar eclipses.
- Nodal precession: the line of nodes precesses (retrograde) around the ecliptic in about 18.6 years, shifting where eclipse seasons occur.
True Node vs. Mean Node (ephemerides)
- Mean Node: an averaged motion—always retrograde.
- True Node: includes short‑term oscillations—can briefly turn direct.
- Separation: typically within about a degree (often cited within ~1–1.5°).
Most ephemerides let you choose which node to display; charts often show only the North Node (the South Node is exactly opposite).