Systematic deformations of the apparent almucantar as derived from Danjon astrolabes in Paris and Santiago de Chile

Abstract

Systematic deformations of apparent almucantar based on long series of observations with Danjon astrolabes in Paris and Santiago de Chile are derived. It is shown that their amplitudes of order of 0".1 - 0".2 have significant seasonal character. Comparison of the results based on two different catalogs (FK4 and FK5) make us believe that at least 50% of the deformations found are caused by local azimuth-dependent refraction anomalies. Consequently, the model used in the present study will become an important part of the algorithm used for the prepared new solution of Earth orientation parameters in the Hipparcos reference system.