ARCHAEOASTRONOMICAL REFRACTION RECONSIDERED

Abstract

Most investigations of refraction for archaeoastronomical research have been based on observations over flat

terrain (Sampson 1994) or over a depressed horizon (Schaefer & Liller 1990). Such observations are not

representative of the elevated distant foresights found in most archaeoastronomical sites. It has been shown

(e.g. Young 2004) that the magnitude and variability of refraction is exceptionally strong near the horizon

and decreases rapidly with increasing angular altitude.

A recent study of refraction in archaeoastronomical contexts has demonstrated from meteorological

principles the influence of strong temperature gradients near the earth's surface, the importance of local

topography on refraction for low lines of sight, and from geometrical analysis the importance of refraction

near the distant horizon marker and the relative unimportance of refraction near the observer. Quantitative

investigation of this phenomenon shows that the magnitude of refraction at elevated horizon markers is

reduced by one to two orders of magnitude in comparison to refraction over flat terrain (McCluskey 2017).

The current investigation extends the previous study to consider geometric factors as they relate to the

calculation of refraction, the variability of atmospheric refraction, and the relative importance of different

meteorological parameters. This investigation closes by discussing the methods of computing refraction that

are appropriate to various levels of precision.

The results of this investigation and of prior work (McCluskey 2017) account for the consistency inferred

from ethnographic reports of Puebloan astronomical observations and call for a positive reevaluation of the

possible precision of archaeoastronomical alignments to distant horizon markers.