(1) Observatorio Nacional/CNPq - Brazil
(2) Observatorio do Valongo/UFRJ - Brazil
(3) Pulkovo Observatory - Russia
A group of over 51 stars, with confirmed radio emission and mostly with published radio positions, were observed by astrographical means. Additionally, 2 radio-stars of fainter magnitude were observed using a CCD direct camera with a long focus, large aperture telescope. The distinct methods of reduction are presented.
The optical reductions are made relative to four catalogues: the Carlsberg Meridian Catalogue \#4, the International Reference Stars Catalogue, the Positions and Proper Motion Catalogue and the Astrographical Catalogue of Reference Stars. The typical standard error of the radio star positions is 0"07 for both right ascension and declination. We compare the outcome from the different catalogues of reference.
The radio positions were collected from the literature. Most of them were obtained at the Very Large Array, while another substantial part has VLBI position. The optical minus radio results are analyzed. The lengths of arcs between the optical and radio positions of pairs of stars are calculated and the arc differences are formed. They allow to discuss the accuracy of the secondary reference frame formed by radio positions of stars. We compare the results so obtained with those that can be drawn from the VLA list of astrometric position of radio stars.