2026-04-17T18:37:05Zivo://CDS.VizieR/J/A+A/567/A262026-03-18T07:59:19ZJ.A_AIVOANew standards in 18th century astrometryThe present high accuracy of stellar positions and proper motions allows us to determine the positional accuracy of old stellar catalogues. This has already been done for the most important catalogues from before the 18th century. Our aim is to extend this study to several 18th century catalogues. To do this, I studied ten catalogues: those of Flamsteed and Romer, four catalogues of La Caille, and catalogues of Tobias Mayer, Bradley, Piazzi, and Lalande. A comparison with modern data, mostly from Hipparcos, compiled in the Simbad data base of the CDS allowed me to determine the position errors of these catalogues. I also compared the stellar visual magnitudes given in eight of these catalogues with photometric V magnitudes. Thanks to novel instruments, the r.m.s. positional accuracy improved from thousands to hundreds of arc seconds in older catalogues to less than one minute in that of Flamsteed, and to 2-6 arcseconds in the other catalogues I examined. These improvements allowed for the first time relatively accurate proper motions to be determined by 19th century astronomers.astrometrysurveysobservational-astronomyhttps://dc.g-vo.org/rr/q/lp/custom/CDS.VizieR/J/A+A/567/A26http://doi.org/10.26093/cds/vizier.35670026https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/567/A262014A&A...567A..26Lhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/567/A26Cone search capability for table J/A+A/567/A26/flamstee (Flamsteed (from Lalande 1783))Cone search capability for table J/A+A/567/A26/romer (Romer (from Galle 1845))Cone search capability for table J/A+A/567/A26/lacaifun (La Caille, fundamental stars (La Caille, 1757))Cone search capability for table J/A+A/567/A26/bailly (La Caille/Bailly, fundamental stars (Anonymous (Bailly) 1763))Cone search capability for table J/A+A/567/A26/lacaisur (La Caille, southern survey (La Caille, 1847))Cone search capability for table J/A+A/567/A26/lacaizod (La Caille, zodiacal stars (Anonymous (Bailly) 1763))Cone search capability for table J/A+A/567/A26/mayer (Mayer, zodiacal stars (from Baily 1831))Cone search capability for table J/A+A/567/A26/bradley (Bradley (from Bessel 1818))Cone search capability for table J/A+A/567/A26/piazzi (Piazzi (Piazzi 1814))Cone search capability for table J/A+A/567/A26/lalande (Lalande (from Bossert 1892))Lequeux J.CDS2015https://cds.unistra.fr/vizier-org/licences_vizier.htmlCDS support team <cds-question@unistra.fr>DatasetAstroObjectsastronomy