Ecliptic

What it is

The ecliptic is the line the Sun appears to trace against the stars over a year. It is really the flat plane of Earth’s orbit, projected onto the sky. Because the whole solar system is nearly flat, the Moon and planets never stray far from this same line, which is why the zodiac is a narrow band rather than scattered across the whole sky.

Why astrology leans on it

The zodiac is measured along the ecliptic, and so is every position in a chart. When Hali says a planet is at six degrees of Scorpio, it means six degrees along the ecliptic from the start of that sign. The ecliptic is the ruler every chart is drawn against, and the tropical zodiac simply marks it off from the spring equinox.

The equinoxes and solstices

The ecliptic is tilted against the celestial equator, the projection of Earth’s equator onto the sky, by the same angle as the Earth’s axis. The two great circles cross at two points. When the Sun reaches the crossing heading north it is the March equinox, the start of Aries, and when it reaches the other crossing it is the September equinox, the start of Libra. Halfway between, the Sun is furthest north at the June solstice, the start of Cancer, and furthest south at the December solstice, the start of Capricorn. The seasons are the ecliptic’s tilt made visible.

How to find it in the sky

You can trace it on any clear night by joining the Moon and whichever bright planets are up. They will sit roughly in a line, and that line is close to the ecliptic. Bright stars on it or very near it include Regulus in Leo, Spica in Virgo, Antares in Scorpius and Aldebaran in Taurus, and the Moon regularly passes close to all four.

How Hali uses it

Hali calculates the apparent position of each body and rotates it into ecliptic coordinates of date, using the true tilt of the Earth’s axis at your moment of birth. The number that comes out, the ecliptic longitude, is what places a planet in a sign. A planet’s distance above or below the ecliptic, its latitude, does not change its sign.

Common confusions

The ecliptic is not the horizon and not the celestial equator, and it is not fixed in the same place in your sky every night. Because it is tilted, it rides high in some seasons and low in others. The Ascendant and Midheaven are simply the two points where the ecliptic meets your horizon in the east and your meridian overhead. The tropical zodiac page explains how the ecliptic is divided into signs.