The reference sky

Astrolabes & MUL.APIN

First the astrolabes filed three stars under every month; then two tablets, named after the Plough star that opens them, put the whole visible sky in order: sixty-six stars and constellations in three celestial paths, a calendar of their risings, the moon's road through eighteen figures that would one day be trimmed into the zodiac, the five planets, and the rules and clocks that kept Babylonian time honest.

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tablets
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paths of the sky
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stars and constellations

Inside the compendium

MUL.APIN is a filing system for the sky: star lists, rising dates, the moon's path, planetary periods, calendar rules and clocks, each section a tool the omen scholars reached for nightly.

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The Plough that names it

the incipit mulAPIN

Like most cuneiform works, the compendium is named from its first words, and its first words are its first star: mulAPIN, the Plough. The star list opens with it, and the whole two-tablet work has been filed under the name of one constellation ever since.

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The three paths of the sky

Enlil · Anu · Ea the grand division

Every star belongs to one of three bands: the northern path of Enlil, the equatorial path of Anu, and the southern path of Ea. Where a star rises on the eastern horizon files it under its god. It is the first known scheme to organise the entire sky by celestial geography.

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The sixty-six stars

Tablet 1 the catalogue

The opening section lists sixty-six stars and constellations path by path, each with its divine associations: the Plough, the Old Man, the Great Twins, the Bull of Heaven, the True Shepherd of Anu, the Fish, the Scorpion. It is the fullest surviving map of how Babylon saw its night sky.

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The calendar of risings

Tablet 1 the ideal year

Next comes a schedule: which stars rise heliacally on which dates of an idealised 360-day year, together with stars that rise as others set. With it a scholar could check the sky against the calendar, and the calendar against the sky, on any clear night of the year.

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The stars of the zenith

Tablet 1 ziqpu stars

A special list names the ziqpu stars, those that culminate overhead in sequence through the night. Watching which one stood at the zenith told the hour in the dark, and eclipse reports timed their observations by exactly these stars. A clock made of geography.

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The path of the moon

Tablet 1 the zodiac's ancestor

The compendium lists the constellations the moon travels through month by month: the Bull, the Twins, the Crab, the Lion, the Furrow, the Scales, the Scorpion, the Goat-Fish, the Hired Man and their companions, eighteen figures in all. Cut down to twelve equal signs centuries later, this list became the zodiac.

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The five wanderers

Tablet 2 planetary periods

The second tablet turns to the bodies that keep no fixed place: Jupiter, Venus, Mars, Saturn and Mercury, with the stretches of time each stays visible and invisible. The numbers are rough schemes rather than theory, but they are the seed of every later planetary period.

➕

Keeping the calendar honest

Tablet 2 the thirteenth month

Twelve lunar months fall short of a year, so the calendar drifted until a thirteenth month was inserted. MUL.APIN gives the rules: watch where the moon stands against the Pleiades and other markers, and when the sky disagrees with the date, intercalate. Astronomy in the service of bookkeeping.

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Shadows and water

Tablet 2 telling the time

Tables give the length of a gnomon's shadow through the day and the weight of water in a clock through the night, with the longest night set at twice the shortest in the schematic Babylonian ratio. Between shadow, water and the ziqpu stars, the compendium covers the clock around.

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Before it: the Three Stars Each

Assur & Babylon c. 1100 BCE

MUL.APIN had a forerunner: the so-called astrolabes, lists assigning three stars to each month, one in each path, thirty-six in all, arranged in circles or grids. The compendium absorbed, corrected and outgrew them, but the astrolabes show the filing system already forming a century or more earlier.

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The omen appendix

Tablet 2 the purpose showing

The compendium closes with a run of celestial omens. The placement says everything about what the work was for: the star lists, calendars and clocks existed so that the signs of Enuma Anu Enlil could be caught, timed and named correctly. Reference astronomy grew as divination's toolkit.

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Forty manuscripts

Nineveh · Assur · Babylon · Uruk 687 BCE and after

Around forty copies and fragments survive from cities across Assyria and Babylonia, the oldest dated one written in 687 BCE, with the contents likely compiled around 1000 BCE or earlier. A text copied that widely for that long was not literature; it was equipment.

The collector and the decipherers

The king whose library preserved the finest copies, and nine scholars across three centuries who identified the constellations, reconstructed the system and put the compendium into modern editions.

Ashurbanipal

reigned 668–627 BCE Nineveh

The scholar-king whose library at Nineveh preserved fine copies of the compendium alongside the omen series it served. His collection is why the Babylonian reference sky can still be read today.

Peter Jensen

1861–1936 Germany

Pioneer of Babylonian cosmology whose 1890 study began the work of matching cuneiform star names to real constellations, the identification game every later edition has continued.

Franz Xaver Kugler

1862–1929 Netherlands

Jesuit scholar whose volumes on Babylonian star lore reconstructed the system of paths, risings and calendar schemes within which MUL.APIN makes sense.

Ernst Weidner

1891–1976 Germany & Austria

Surveyed the whole of Babylonian astronomy in his 1915 handbook, treating the astrolabes and the compendium's material, and spent a career sorting the tablets they survive on.

Johann Schaumberger

1885–1955 Germany

Completed Kugler's great work after his death, refining the star identifications and the astronomical calculations behind the Babylonian lists.

Bartel van der Waerden

1903–1996 Netherlands & Switzerland

Mathematician and historian of science whose studies of the thirty-six stars and the birth of astronomy placed the astrolabes and MUL.APIN in the long story that leads from star lists to mathematical astronomy.

David Pingree

1933–2005 United States

Co-produced the first full modern edition of MUL.APIN in 1989, and traced how its star lore travelled into the astronomies and astrologies of India, Iran and Greece.

Hermann Hunger

born 1942 Austria

Co-editor of both modern editions of the compendium, in 1989 with Pingree and in 2018 with Steele, and editor of much of the observational corpus that surrounds it.

Wayne Horowitz

born 1957 Israel

Edited the astrolabes, the Three Stars Each lists that preceded the compendium, and mapped the cosmic geography of the paths of Enlil, Anu and Ea in Mesopotamian thought.

John Steele

born 1971 Britain & United States

Co-editor with Hunger of the 2018 edition, the current standard, which re-collated the forty manuscripts and re-examined what the compendium's schemes were actually for.

What MUL.APIN is

MUL.APIN is the reference handbook of Babylonian astronomy before the invention of the zodiac and the mathematical theories: two cuneiform tablets that collect, in fixed order, everything a working scholar needed to know about the ordered sky. It lists the stars and constellations by celestial region, schedules their risings through the year, names the constellations the moon travels through, gives the visibility periods of the five planets, states the rules for correcting the calendar, and tabulates shadow lengths and water-clock weights for telling time. The title is simply its first word: the work opens with the star called mulAPIN, the Plough, and cuneiform works are cited by their opening line. Compiled around 1000 BCE or somewhat earlier from older material, it remained the standard sky reference for the better part of a millennium.

The three paths

The compendium's grand organising idea is a division of the sky into three bands by rising point on the eastern horizon: the path of Enlil in the north, the path of Anu along the middle, and the path of Ea in the south. Every star belongs to one path and one god. The scheme sounds theological, and is, but it works as astronomy: it fixes each star's declination band, so a scholar who knew the paths knew roughly where and when anything would rise. It is the earliest known system that files the entire visible sky, and its echo survives in the modern habit of dividing the heavens into northern, equatorial and southern zones.

The catalogue and the calendar of risings

Tablet 1 opens with the catalogue: sixty-six stars and constellations, path by path, with their divine associations. Here are the figures of the Babylonian sky in their own order: the Plough, the Old Man, the Crook, the Great Twins, the Crab, the Lion, the Bull of Heaven, the True Shepherd of Anu, the Arrow, the Eagle, the Fish, the Scorpion, the Goat-Fish. Then comes the schedule: the dates, in an idealised 360-day year of twelve thirty-day months, on which the principal stars first rise before dawn, and lists of stars that rise as others set. The two sections together turn the sky into a calendar and the calendar into something checkable against the sky.

The stars of the zenith

A further list names the ziqpu stars: those that pass directly overhead, culminating in a fixed sequence through the night. Their use was horological. On any clear night, the star standing at the zenith told the watch and the hour, and the scholars' eclipse reports time events precisely this way, by which ziqpu star was culminating when the shadow touched the moon. Together with the water clock for cloudy skies, the zenith stars gave Babylon a working night clock centuries before anyone had a name for astronomy as a discipline.

The path of the moon

Buried in Tablet 1 is the compendium's most consequential list: the constellations 'in the path of the moon,' the figures through which the moon, and with it the sun and planets, travel. MUL.APIN counts eighteen, including the Bull of Heaven, the Great Twins, the Crab, the Lion, the Furrow with her ear of grain, the Scales, the Scorpion, Pabilsag the archer, the Goat-Fish, the Great One with his streams of water, the Tails of the fishes and the Hired Man. Trim the list to twelve, make each figure an equal thirty-degree segment, and you have the zodiac, which is exactly what Babylonian astronomers did around the fifth century BCE. Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces and Aries are this list's direct descendants, most of them keeping even their images.

The five wanderers

Tablet 2 turns from the fixed sky to the bodies that will not stay filed: Jupiter, Venus, Mars, Saturn and Mercury. The compendium records the stretches of time each remains visible and invisible, rough period schemes rather than predictive theory. The interest is nonetheless unmistakable: the planets are treated as regular, their absences as measurable, their returns as expectable. Between these crude periods and the exquisite ephemerides of the Seleucid era lies a straight line of refinement running through centuries of the observational diaries.

Keeping the calendar honest

Babylonian months began with the sighting of the crescent, and twelve lunar months fall about eleven days short of the solar year, so the calendar drifted. MUL.APIN supplies the correction rules: watch the moon against the Pleiades and other markers, watch which stars rise in which months, and when sky and date disagree by a month, insert a thirteenth month. The compendium also fixes the ideal frame, placing equinoxes and solstices on the fifteenth of months one, four, seven and ten of the schematic year. Intercalation stayed a case-by-case scholarly judgement for centuries before settling into the regular nineteen-year cycle of the late period, the same cycle that still schedules Easter and the Jewish calendar.

Shadows and water

The compendium's final technical sections are clocks. One table follows the shadow of a gnomon, a vertical rod, through the hours of the day at different seasons. Another gives the weights of water to be poured into the night clock so that it runs out at daybreak, with the longest night weighted at twice the shortest, the characteristic 2:1 ratio of Babylonian schematic astronomy, tidier than Babylon's real latitude allows. Day by shadow, night by water and zenith star: the toolkit covers the full round of the clock, because an omen unreported at the right watch was an omen wasted.

Before it: the Three Stars Each

MUL.APIN did not invent its filing system. Older lists, conventionally called astrolabes though they are nothing like the later instrument, assign three stars to each month of the year, one from each path, thirty-six in all, sometimes drawn as concentric circles divided into twelve. The finest, Astrolabe B from Assur, dates to around 1100 BCE. The compendium absorbed their scheme, corrected their placements and superseded them, but they show the Babylonian passion for celestial bookkeeping already fully formed in the second millennium.

The omen scholars' textbook

Tablet 2 ends with a run of celestial omens, and the appendix gives the game away: MUL.APIN existed to serve divination. The scholars who watched for the signs of Enuma Anu Enlil needed to know which star was which, when its rising was due, whether the calendar was in step with the sky, and what the hour was when something happened. The compendium answers exactly those questions. In the reports to the Assyrian kings, the two works operate as a pair: MUL.APIN says what the sky should be doing, the omen series says what it means when the sky does otherwise. It is reference astronomy and applied astrology bound in one curriculum, and the scribes saw no seam between them.

Copies and editions

Around forty manuscripts and fragments survive, from Nineveh, Assur, Kalhu, Babylon, Uruk and elsewhere, the oldest dated copy written in 687 BCE and the contents plainly older, with most scholars placing the compilation around 1000 BCE and some of its observations earlier still. The modern editions are the work of the same small guild that recovered the rest of Babylonian astronomy: Hermann Hunger and David Pingree's edition of 1989, and the current standard, Hermann Hunger and John Steele's of 2018, with Wayne Horowitz's edition of the astrolabes covering the forerunners. Thanks to them, the oldest surviving handbook of the sky can be read cover to cover.

How to read this section

The cards above follow the compendium's own architecture: the three paths and the catalogue, the calendars and clocks built on them, the moon's path that became the zodiac, the planets, the forerunner astrolabes and the omen appendix that reveals the purpose. For the omen series this handbook served, see the Enuma Anu Enlil page; for the tradition around both, the Babylonian omen astrology page. MUL.APIN and its sky are part of the Tarot Academy compendium in all fifty-two languages.

Frequently asked questions

Babylonian omen astrology

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