My paper examines several drawings of Babylonian planets and star constellations in tablets from the Seleucid period, which represent part of my ongoing project on the micro-zodiac. I clarify certain misunderstandings in Weidner’s study of these tablets (1967) concerning the notion of “micro-decans,” numbers assigned to lengths of daylight, and in particular the role of measurements in the positioning of planets and constellations.
In these drawings, constellations sometimes replicate stars found in other depicted constellations, and their sizes are out of proportion to each other. More curiously, the orientations of constellations are mirror images of those actually observed from the earth's perspective, so that the drawings cannot be understood as direct depictions of any celestial scene. I propose that these drawings were constructed using a horizontal scale, not of spatial distances, but of temporal measures. Below the drawings, the tablet’s width is divided into twelve equal columns, each devoted to written discussion on a micro-zodiac sign (2½°) that represents the twelfth-part of a single zodiac sign (30°). These columns do not only partition the written text, but also constitute the divisions of a horizontal axis at the base of the drawing. In addition, some drawings further divide their horizontal axis into thirty units (1° each) corresponding to the 30 days of an ideal Babylonian month.
The tablets also mention months in which lunar eclipses occur, as well as numbers related to the length of daylight in specific months in Babylonian astrolabes. These features enable us to assign absolute (if ideal) date ranges to the horizontal axes of our drawings. I show that the left edges of constellation drawings are made to line up according to the ideal dates of their heliacal rising in the astronomical compendium MUL.APIN. The drawings, in effect, represent temporal intervals between dates as the spatial dimensions of a celestial scene. The tablet convention of numbering dates from left to right resulted in the mirror reversal of star constellations in our drawings.
The planets (moon, Jupiter, Mercury) in our drawings provide independent verification of my proposed scale, since these planets do not move like the fixed star constellations and were not positioned using the same method. Weidner earlier noticed that the planets are depicted in their “house of secret” positions, which correspond to the Greek hypsomata. While Babylonian texts do not define these positions precisely, Greek texts allow us to locate hypsomata in terms of degrees within a zodiac sign. The planets in our Babylonian drawings, on the other hand, correspond to “dates” that can be related in linear equation to the degree positions of Greek hypsomata.