On Astronomical Refraction

This paper has given a general account of the reasons for generation of astronomical refraction and its affects on the astrometric observations, and of the early and modern theories about astronomical refraction as well as the models established from these theories. The main problem is that these theories couldn't describe the atmospheric conditions objectively, Which resulted the unaccuracy of the refractional tables, especially in the case of greater zenith distance. The importance of measuring the astronomical refraction on the real time by new ways-meridian circle is emphasized.