SIMBAD references

The optical minus radio positions of 17 radio stars, originally determined by Johnston et al. (1985), are compared with the average AGK3 minus FK5 offset in the neighborhood of each star. A positive correlation is found at the levels of 0.90 for right ascensions and 0.99 for declinations. A similar comparison is made, to access the southern region, for 14 extragalactic radiosources, presented by White et al. (1990), matching the average Perth70 minus FK5 offsets. A lower correlation is found, at the levels of 0.71 for right ascensions and 0.69 for declinations, possibly due to magnitude and color effects. These results would indicate that inhomogeneities in the optical reference system can systematically contribute to the differences between optical and radio positions.