Ecliptic latitude

Meaning

The zodiac runs along the ecliptic, the circle the Sun seems to trace through the stars in a year. The Moon and the planets keep close to it, but not exactly on it, because their orbits are tilted a little to the Earth’s. A body’s ecliptic latitude is how far north or south of the ecliptic it stands, in degrees. Its zodiac degree, the longitude, says how far along the circle it is; the latitude says how far off to the side.

A chart drawn as a wheel leaves the latitude out. Each body is placed by its longitude alone, as if dropped straight onto the ecliptic, and its sign and degree do not change with its latitude. The latitude is still there in the sky, and it explains a few things a wheel cannot show.

In practice

• How far: the Sun stays on the ecliptic by definition. The Moon wanders up to about 5° either side. Mercury, Venus and Mars, when close to the Earth, can reach several degrees. Pluto, on a steeply tilted orbit, reaches about 17°, and Pallas and Eris, more tilted still, can stand tens of degrees off it.
• The nodes are the two points where the Moon crosses the ecliptic, from south to north at the North Node and back at the South Node. There its latitude is zero.
• Eclipses happen only when a New or Full Moon falls near a node, with a latitude small enough for the Sun, the Moon and the Earth to line up in the sky and not only in longitude.
• Conjunctions: two bodies at the same zodiac degree can be far apart in the sky if their latitudes differ. When both their longitudes and latitudes match, one can pass in front of the other, an occultation. The same holds for a fixed star far from the ecliptic: conjunct a planet by degree, it may shine in quite another part of the sky.
• Declination: a body’s distance from the celestial equator depends on its latitude as well as its longitude, which is how the Moon and the planets can go out of bounds.

Across traditions

• Human Design reads the planets’ gates from their zodiac longitude alone, so latitude plays no part there.
• Chinese astronomy measured the sky mostly from the equator: its catalogues give a star’s distance from the celestial pole rather than from the ecliptic, a measure closer to declination.

Origin and history

Greek astronomers measured positions in both coordinates. Ptolemy’s Almagest gives a catalogue of more than a thousand stars, each with its longitude and latitude along the ecliptic, and a separate theory for the latitudes of the planets, which he knew to wander north and south of the Sun’s path. Astrology kept the longitude for the signs, the aspects and the houses, and let the latitude fall into the background. Modern astronomy, as set out in Jean Meeus’s formulas, still gives every body its ecliptic latitude beside its longitude.

How Ulune calculates it

• Each body’s ecliptic latitude comes from the Swiss Ephemeris with its longitude: its apparent position, seen from the centre of the Earth, referred to the ecliptic of the date.
• The Table’s Points part shows it, signed, for the bodies: the planets, Chiron, the asteroids, Eris, Sedna and Lilith. The nodes lie on the ecliptic by definition, and the angles, the Vertex and the lots are points of the ecliptic, so none of them has a latitude to show.
• The latitude is never used to place a body in a sign or a house, nor to measure the aspects.
• It enters the declination of each body, and the Moon’s latitude enters the lit share of its disc in the Chart part’s Moon phase.
• Without a birth time, the figures that could change over the day are marked ~.