(Submitted to: Astronomy and Astrophysics, Supplement Series)
From the measurement on the Digitized Sky Survey of the optical position of 153 QSOs with an accurate absolute VLBI position, we have determined that the r.m.s. uncertainties of these measurements is ~ 0.6 arcsec in both coordinates over the whole sky, except for objects located near one edge of the plate. We have measured the optical position of 607 AGNs (or AGN candidates). For many of these objects, the accuracy of the published optical position was 1 arcmin or worst.
Key words: astrometry; quasars