In this paper we give new results of a decade-old program to determine precise
optical positions for the optical counterparts of compact extragalactic radio
sources (CERS) being considered as possible Benchmark objects to link the new
high-precision VLBI radio reference frame (see e.g. Johnston et al. 1995,
hereafter Johnston), with the optical reference frame. Of the roughly 600
objects that have been or are present being considered as possible link
sources (Fey 1994), we have obtained homogeneous optical positions at a
precision level as good as 0.1
in both coordinates for about 250 of them by
means of routine observations carried out with a flat-field 70/100/210 cm
Maksutov astrograph. Comparison of our optical data with available VLBI radio
positions has allowed us to uncover misidentifications and unsuitable link
objects -thus contributing to the basic goal of selecting the most adequate
Benchmark sources- and to evaluate the existence of offsets between the radio
and the optical frames as defined at present (see e.g. Costa & Loyola 1996,
and references therein).
Here we present new optical observations of 40 southern CERS selected mainly from the list of Jauncey et al. (1989), hereafter Jauncey. The optical positions were measured with respect to the stars of the IRS catalogue (Corbin 1991), and therefore are given in the system of the FK5.
Figure 1: Finding chart for 1236-684. Chart is 9 arcmin on a side. See
Sect. 4
for details