Instituto Astronomico e Geofisico - Universidade de Sao Paulo
Av. Miguel Stefano, 4200
04301-904 Sao Paulo, Brazil
Following a IAU recommendation, B5 resolution on the Working Group on Reference Frames, we started at Valinhos (Brazil) Observatory, an observational program of a subset of the extragalactic radio source list provided by IAU (Bull. 74 January 1995). The scientific goal of these observations is to establish the connection between the optical and radio reference systems.
In collaboration with the Bordeaux Observatory, a new CCD micrometer was fitted to our transit circle. Sources brighter than V=16.5 can be observed with a positional accuracy between 0.04" and 0.08". The optimal magnitude range lies between V=9 and V=14.
For each source we observe a zone of 13' in declination and 30 to 60 min. in right ascension, centered on the source. Each zone contains about 20 reference stars, presently taken from the PPM catalog.
The data yield a V magnitude estimate, as well. The achieved accuracy is better than 0.05 and allows a search of eventual variability.
A discussion about the observations and the first positional results of this program is presented here.