Completion of Scanning, Data Releases and Optimization of Analysis and Database for DASCH

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This grant will complete the scanning-digitization and processing of the remaining approximately 200,000 glass plates of the Digital Access to a Sky Century @ Harvard (DASCH) project, the first 100 year (1886-1992) full-sky database of the brightness and positions of 50,000 stars or stellar objects. This data is on 500,000 glass plates contains repeated measurements of the variability of all detected stellar objects. The DASCH project will create an all-sky 100 year photometric record which will allow the discovery and measurement of all classes of stellar and quasar/blazar variability on time scale of hours-days to many decades. By measuring historic outbursts of black hole-low mass X-ray binaries to identify their duty cycle, an estimate can be made of their occurrence in the galaxy. The DASCH data base will make contributions to astrophysical studies as well to education by using the data base in high school curriculum science lessons on astronomy, as well as to meeting the public's interest in the variations of stars in night sky. This grant will preserve the DASCH data base for posterity and make it available to the scientific community and the public. The remaining 200,000 of the 500,000 glass plates in the Harvard Plate Collection will be scanned, digitized, processed and archived. This will allow the study of time variable events of stars and compact extragalactic objects such as quasars over the time period 1886-1992 for astrophysics, history of astronomy and high school science lesions in astronomy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.