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First Data Release from DASCH

Wednesday, May 1, 2013 - 16:49

The first of 12 planned Data Releases, DR1, for production scanning of the ~500,000 Harvard glass plate images covering the full sky from 1885 to 1992, has been released at

The Digital Access to a Sky Century @ Harvard (DASCH) project (see Grindlay et al. 2012 and references therein) has developed the precision high-speed scanner and software pipeline for processing the digital images with WCS (UCAC4) for each plate. Photometry is calibrated (~0.1 mag) spatially against the GSC 2.3.2 or APASS catalogs, and astrometry and lightcurves of all resolved objects on each plate are derived down to the local limiting magnitude, typically B ~12-17, depending on plate series. Results are stored in a MYSQL database and file system that allows rapid (~10 sec) extraction of lightcurves for any object (up to 10 at a time). Thumbnail images of the object for any point(s) selected in its lightcurve are displayed and can be downloaded.

Production scanning (up to 400 plates/day) is proceeding in galactic coordinates, from the north galactic pole (NGP) down to latitude b = 15 deg; then the SGP up to b = -15 deg; and finally the galactic plane (b = -15 to +15 deg). DR1 covers b = 90 to 75 deg. This first DASCH data release also includes the five "development fields" (5-degree-radius regions centered on M44, 3C 273, Baade's Window, the LMC, and the Kepler field) that were scanned and processed to develop the DASCH hardware and software systems and plate-processing procedures, as well as conduct early science. Their photometry, particularly in crowded fields, will be further improved when they are processed in production scanning.

The full scanning and final data release (DR12) can be finished by 2016 depending on continued support. Thanks are due to my team members Sumin Tang (UCSB), Edward Los (Harvard-Smithsonian CfA), George Miller (CfA), Mathieu Servillat (CEA/Saclay), Robert Simcoe (CfA), Alison Doane (CfA), Jamie Pepper (CfA), and David Sliski (CfA). We gratefully acknowledge support from NSF grants AST0407380 and AST0909073.

Jonathan E. Grindlay
Harvard-Smithsonian, CfA