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Published online by Cambridge University Press: 12 April 2016
The main purpose of this contribution is twofold. First, we report on a preliminary assessment of the astrometric properties of the CCD system we are presently using to extend the magnitude limit of the Torino program on optical positions of QSO’s. This assessment is based on the internal consistency of the positions derived from different CCD frames of the same objects. Then, we give a first evaluation of the precision of CCD derived QSO positions after extending a plate based reference frame (secondary frame) onto the CCD images (tertiary frame).
Special emphasis is given to comparisons with plate positions of the same faint objects. It is shown that use of the CCD camera promises a factor of five (or larger) improvement in the precision of QSO positions.