Ecliptic

What is the ecliptic?

The ecliptic is the apparent path of the Sun across the sky. Seen from the Earth, the Sun travels once round in front of the stars in a year, just under one degree eastwards each day. Its track is the ecliptic. It is the plane in which the Earth moves around the Sun, carried over onto the sky.

The name comes from the Greek ekleipsis, eclipse. An eclipse only happens when the Moon stands on this line.

Ecliptic, zodiac and celestial equator

Moon and planets move close to the ecliptic, because their orbits lie almost in the same plane as the Earth’s. The Moon’s orbit is tilted by just over 5 degrees, the orbit of Mercury by 7 degrees. The constellations that lie along the ecliptic form the zodiac.

The celestial equator is the Earth’s equator carried over onto the sky. It is tilted by 23.44 degrees against the ecliptic, as far as the Earth’s axis. The two lines cross at the vernal point and at the autumnal point. When the Sun stands there, day and night are the same length.

This tilt makes the ascending and descending Moon. Whatever follows the ecliptic rises above the celestial equator and sinks below it again. The Sun takes a year for this, the Moon just over 27 days.

What in the calendar depends on the ecliptic

• Lunar nodes: the Moon crosses the ecliptic twice a month. Biodynamic practice does not sow or plant in these hours. More under lunar node.
• Planetary nodes: the planets cross the ecliptic too. Dyyna counts twelve hours before and after as unfavourable. More under planetary node.
• Eclipses: they arise when New Moon or Full Moon falls close to a node. More under eclipse.
• Constellations: where the ecliptic passes through a constellation, its boundaries lie in the calendar. More under constellations.
• Positions: conjunction, opposition and trine are measured along the ecliptic, as a difference in ecliptic longitude.

Sources

• Ecliptic, Wikipedia
• Celestial equator, Wikipedia