NOAO >   Observing Info >   Approved Programs >   2001A-0161

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Proposal Information for 2001A-0161


PI: Imants Platais, Yale University, imants@astro.yale.edu
Address: P.O. Box 208101, New Haven, CT 06520, USA

CoI: Terrence M. Girard, Yale University, Department of Astronomy
CoI: William F. van Altena, Yale University, Department of Astronomy

Title: Deep Astrometry of Key Open Clusters

Abstract: We propose to continue determination of cluster membership to very faint magnitudes for the set of fundamental open clusters (NGC 2264, 2682, 6791, 6819, and 7789) as defined by the NSF funded WIYN Open Cluster Study (WOCS). By combining numerous old first-epoch plates taken at the Mayall 4-m telescope with recent CCD Mosaic Imager frames we will be able to derive accurate proper motions down to V~23. We have demonstrated that the ``plate + CCD-Mosaic" astrometry can produce very accurate proper motions (standard error 0.5 mas/yr or better). This is allowing us to obtain complete Present Day Mass Functions down to ~0.5M_\sun, essentially eliminating uncertainty due to field stars. This proposal focuses on i) depth; ii) field coverage - out to two tidal radii; and iii) astrophysical significance of the clusters. Faint galaxies seen in the fields of these clusters provide the means to obtain absolute proper motions which, coupled with radial velocities and a distance, are essential to calculating their Galactic orbits. An important spin-off of our program is the astrometric calibration of the NOAO CCD Mosaic Imager. It appears to show the signs of chip-to- chip gap enlargement which, if unaccounted for, is undesirable in astronomical applications. These observations will provide further evidence on the CCD Mosaic's geometric stability.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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