7 - Untimed Babylonian observations of lunar eclipses: horizon phenomena

Summary

Introduction

In the previous chapter, a variety of Babylonian timings of lunar eclipse contacts were analysed. Several of these records also noted that the Moon rose (ki E-a) or set (SU) whilst eclipsed. Additionally, some damaged texts do not contain useful measurements of time but nevertheless affirm that the Moon was eclipsed at its rising or setting. Such fairly straightforward observations (which enable limits on the value of ΔT to be deduced), would require no instrumental aid. In the following pages these various observations will be investigated together with a few rather more careful reports which give an estimate of the fraction of the Moon covered at moonrise or moonset.

Since the eclipsed Moon is in direct opposition to the Sun, it invariably rises close to sunset or sets near sunrise. It thus usually reaches the horizon when the sky is quite bright – often when the Sun is above the opposite horizon. However, as noted in chapter 4, despite these seemingly unfavourable conditions the Babylonians systematically measured the time of moonrise (relative to sunset) and moonset (in relation to sunrise) around full Moon with considerable care. Many examples of this practice are found in one of the earliest surviving astronomical diaries – dating from 568 BC, the 37th year of Nebuchadrezzar II (see SH I, pp. 47 ff.) – and it may extend back much further in time.