Astrometric Accuracy of Positions

Abstract

The great development of astrometric accuracy since the observations by the Greek astronomer Hipparchus about 150 BC has often been displayed in diagrams showing the accuracy versus time. Two new diagrams are provided here, one for positions only, another including parallaxes. New information is included on the Gaia DR3 data and the coming data releases, and about two great astronomers from the distant past, Wilhelm in Kassel and al-Sufi in Isfahan.