Dynamical analysis of nearby clusters Automated astrometry from the ground: precision proper motions over a wide field

Context. The kinematic properties of the different classes of objects in a given association hold important clues about the history of its members, and offer a unique opportunity to test the predictions of the various models of stellar formation and evolution. Aims. DANCe (standing for dynamical analysis of nearby clusters) is a survey program aimed at deriving a comprehensive and homogeneous census of the stellar and substellar content of a number of nearby (<1 kpc) young (<500 Myr) associations. Whenever possible, members will be identified based on their kinematics properties, ensuring little contamination from background and foreground sources. Otherwise, the dynamics of previously confirmed members will be studied using the proper motion measurements. We present here the method used to derive precise proper motion measurements, using the Pleiades cluster as a test bench. Methods. Combining deep wide-field multi-epoch panchromatic images obtained at various obervatories over up to 14 years, we derived accurate proper motions for the sources in the field of the survey. The datasets cover approximate to 80 square degrees, centered around the Seven Sisters. Results. Using new tools, we have computed a catalog of 6 116 907 unique sources, including proper motion measurements for 3 577 478 of them. The catalog covers the magnitude range between i = 12 similar to 24 mag, achieving a proper motion accuracy <1 mas y(-1) for sources as faint as i = 22.5 mag. We estimate that our final accuracy reaches 0.3 mas yr(-1) in the best cases, depending on magnitude, observing history, and the presence of reference extragalactic sources for the anchoring onto the ICRS.