Declination

Meaning

Imagine the Earth’s equator projected out onto the sky: that great circle is the celestial equator. A body’s declination is how far north or south of it the body stands, from 0° on the equator to 90° at either celestial pole. It is written with a sign, + for north and − for south, or with N and S. Declination works for the sky the way latitude works for a map of the Earth.

The zodiac is measured along another circle, the ecliptic, the Sun’s yearly path, which is tilted to the equator by about 23°26′. So two planets can stand at very different zodiac degrees and yet at the same height north or south, and two planets at the same degree can differ in declination. Declination is a second dimension of the chart, beside the familiar longitude.

The Sun’s declination follows the seasons: 0° at the equinoxes, about 23°26′ north at the June solstice and as far south at the December one. The Moon and the planets, whose paths are tilted a little to the ecliptic, can go beyond those limits.

In practice

• Parallels: two bodies at the same declination on the same side of the equator are parallel, read like a conjunction; on opposite sides they are contra-parallel, read like an opposition.
• Out of bounds: a body whose declination goes beyond the Sun’s greatest is out of bounds, read as acting outside the usual rules.
• Height in the sky: for someone in the northern hemisphere, a body far north rises early, climbs high and sets late; one far south stays low and is above the horizon for a shorter time. The reverse holds south of the equator.
• The Moon swings between north and south each month. Every 18.6 years its range grows to about 28½° either side, at its major standstill; the last one peaked around 2024 and 2025.

Across traditions

• Chinese astronomy placed the stars by the equator rather than the ecliptic. Its twenty-eight lunar lodges are measured along the equator, and a star’s place was given by its distance from the celestial pole, a measure close to declination.
• Western astrology has mostly worked in longitude, and declination stayed a specialist’s tool for centuries.

Origin and history

Greek astronomers knew both circles and the angle between them. Ptolemy’s Almagest gives a table of the declination of each degree of the ecliptic, from a tilt he took as close to 23°51′, a little more than its true value in his day. The tilt itself changes slowly: it now shrinks by about 47″ a century, as the formulas Jean Meeus collected show.

Today declination is read mainly through the parallels and the out-of-bounds planets. Twentieth-century astrologers brought it back into practical use, and Kt Boehrer’s Declination: The Other Dimension, in 1994, did much to spread the reading of out-of-bounds planets.

How Ulune calculates it

• Each body’s declination comes from the Swiss Ephemeris, in equatorial coordinates of the date: apparent positions, seen from the centre of the Earth, referred to the true equator. The body’s ecliptic latitude is included.
• The Ascendant, the Descendant, the Midheaven, the IC and the Vertex lie on the ecliptic, so their declination follows from the longitude and the true obliquity of the ecliptic on the date. The South Node’s is the North Node’s with the sign reversed. The lots have none.
• The Table’s Points part shows each declination, signed, to the second of arc, or to the minute without a birth time, when it is marked ~.
• The same declinations feed the parallels of the Aspects part, within 1°, and the out-of-bounds note.