Eclipse

Meaning

An eclipse happens when the Sun, the Moon and the Earth line up closely enough for one to hide another. At a New Moon the Moon can pass in front of the Sun, a solar eclipse; at a Full Moon it can pass through the Earth’s shadow, a lunar eclipse. The Moon’s orbit is tilted about 5° to the Sun’s path, so most New and Full Moons pass above or below: an eclipse needs one near the two points where the paths cross, the lunar nodes.

Astrology has always given eclipses weight. A New Moon marks a beginning and a Full Moon a culmination; an eclipse is read as a stronger one of each, a turn whose effects unfold over months rather than days. Read calmly, an eclipse points to the part of a chart where something is changing, not to a misfortune.

In practice

There are between four and seven eclipses a year. They come in eclipse seasons about six months apart (173 days), each usually holding a solar and a lunar eclipse a fortnight apart.

• A solar eclipse is total, annular (the Moon too far from the Earth to cover the whole Sun, leaving a ring of light), hybrid (total along part of its path, annular along the rest) or partial.
• A lunar eclipse is total, partial or penumbral (the Moon only in the Earth’s faint outer shadow).
• Eclipses come back in a similar form after a saros of 223 lunar months, about 18 years and 11 days.

A reading looks at the sign and degree of an eclipse, the house of a chart it falls in, and the planets and angles of that chart within a few degrees of it. Each eclipse is also a New or Full Moon, read with the transits of its season.

Origin and history

Eclipses are among the oldest recorded events of the sky. Herodotus tells of an eclipse of the Sun that stopped a battle between the Lydians and the Medes, and says that Thales of Miletus had foretold its year; it is usually identified with the eclipse of 28 May 585 BC. Babylonian astronomers kept records of eclipses over centuries and used their 18-year cycle to foresee them.

Ptolemy’s Almagest, about 150, sets out a full theory of the eclipses of the Sun and the Moon, and his Tetrabiblos makes the eclipses the first and strongest of the signs it reads for whole countries and cities.

How Ulune calculates it

The calendar finds each eclipse with the Swiss Ephemeris’s own searches, which give the moment of greatest eclipse anywhere on Earth and its type: total, annular, hybrid, partial or penumbral. Ulune gives its magnitude as NASA does: for a solar eclipse, the share of the Sun’s diameter covered, or the ratio of the two diameters when the eclipse is central; for a lunar eclipse, the umbral magnitude, or the penumbral one when the Moon misses the umbra. The longitude of the Sun or of the Moon at that moment places the eclipse in the zodiac.