Abstract
Latitude and azimuth determination were crucial for Polynesian navigators,
supplemented by techniques such as observations of swells, birds and expanded
landfalls. Longitude could only be determined by dead reckoning. Both latitude and
azimuth made extensive use of stars, which alter gradually over the centuries due to
precession, the movement in the Earth’s axis of spin. Knowledge about the effects of
precession can assist scholars in weighting one voyaging date higher than another,
or in providing possible reasons why certain voyages took place in a particular era if
navigation methods depended on star configurations that were particularly favourable
in that era. The influence of precession on stars used for different methods of latitude
determination is not intuitive. In this article a graph of the change in declination per
century as a function of right ascension is proposed as a way of understanding the
influence of precession on different methods of latitude and azimuth determination,
and of deducing when and where significant configurations occur.