Spectral classification systems and photometry needed in calculations for atmospheric refraction

In ground-based measurements of exact positions of celestial objects on the sky the astronomical atmospheric refraction should be taken into account. In our calculations for refraction we use the Stone code (Stone 1996) where the mean refraction is computed by integrating numerically across the passband with Simpson's Rule. The code has been modified for the case of the 10″ LX200 telescope installed at the Lohrmann Observatory in Dresden. Tabulations of stellar spectral energy from Sviderskiene (1988) together with the quantum efficiency of the CCD detector being used, are applied. We have estimated the accuracies of stellar classification required to achieve the desirable accuracies in calculated refraction, the influence of ground-based atmospheric parameters has been discussed too. Some examples of the spectral classification systems which may provide the required classification accuracies, are given. The special case of computing differential refraction has also been considered. We justify the usefulness of photometric $V-R$ and $V-I$ indices in calculating refraction. Observations are planned to compare calculated and true refraction.