Les tables de réfraction astronomique

Abstract

The paper investigates the refraction as it concerns position astronomy and the attempts of generations of astronomers since Tycho Brahe to estimate its size as a function of the apparent zenith distance of the sources. A few historical models are introduced and their value discussed by comparison to modern tables. The fundamental equation of the light-rays is established starting from the Fermat principle, together with a sample of analytical approximations of its solution down to the end of the XIXth century. Finally the two numerical approaches used today are presented with some details alongside the standard model of the Earth atmosphere. Theoretical expressions are developed step by step to allow the coding into a computer program.

Keywords

• réfraction
• astronomie
• astrométrie
• tracé de rayon
• optique atmosphérique
• histoire de l’optique