Refraction is a very important aspect of geodesy and astronomy: it is one of the main sources for troubles, papers and dissertations, at least in geodesy. Particular important is the vertical refraction because of the up- and down-asymmetry in the atmosphere. However, we must not forget that gravity does not only cause the asymmetry of the atmosphere, also the asymmetry of the mechanical parts of the instrument (bending of the tube, deformation and excentricity of the axis, etc.) and even an asymmetry of the mind of the observer. See figure 1. If it becomes possible to measure the refraction these effects will often become limiting factors for the accuracy.