controversy. The periods of visibility at conjunction or opposition also depend on the
varying length of day, the latitude of the Moon, and the angle of the ecliptic. All
five effects were successfully handled. Most striking is that ephemerides belonging
to what is known as ‘System A’^19 are all connectable. They form one ephemeris with
predictions dating from 476 BCto 42 AD(Britton and Walker 1996 : 61 ). The lunar
ephemerides do provide calendrically useful information, but their prime purpose was
astrological. The length of the month, the date of opposition, the lengths of first and
last visibility,^20 and eclipses were all viewed as ominous signs. The early date for the
invention of the system A mathematical-astronomical lunar model also suggests that
its aim was unconnected to the demands of zodiacal astrology. We should thus assume
that it was invented to assist astrologers undertaking omen divination. In due course,
the data produced by the lunar ephemerides would have proved useful to those writing
horoscopes, for whom the location of the Moon at birth was also significant. It would
appear, though, that eclipse prediction continued to provide the main motivation for
the further development of the lunar models. System B (see note 19 ), attested from
— David Brown —Figure 32. 1 Copy of part of a Babylonian treatise on astronomy and astrology which was used
as a reference source for students at Borsippa. The copy was made by Bel-ahhe-iddina in the year
138 BC. (Courtesy of the Trustees of the British Museum.)