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Digitizing Harvard's Unique Astronomical Plate Collection

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● Largest: 500,000 plates +/- 100,000● Most complete sky coverage: Northern and Southern telescopes● Longest time coverage: 1885-1989 ● Basis for fundamental discoveries in astronomy, such as using Cepheid variable stars as cosmic yardsticks● A legacy of long-term commitment to astronomical photography and researchDigitizing Harvard's Unique Astronomical Plate Collection:Extending the Virtual Observatorya Century Backward in TimeCfA/PSSG, 2002-11-18Without HCO Plate Digitization:● Astronomy will never have any functional record of the sky, 1885-1989.● Astronomy will not have an equivalent time frame for accrued CCD observations until 2080.● Other plate repositories lack the personnel and infrastructure to solve challenges of storage, web display and photometric accuracy which we have in HCO, SAO, and HUL-DRS● Other plate repositories are hoping that Harvard will take the lead in digitization● The upcoming National Virtual Observatory, which provides digital access to astronomical data, will lack its only long-term temporal record of the sky to complement the future LSST digital temporal survey.CfA/PSSG, 2002-11-18IAU Resolution B3, 2000Safeguarding the Information in Photographic ObservationsThe International Astronomical Union, Recognisingthat unless urgent action is taken, this unique historical record of astronomical phenomena will be lost to future generations of astronomers,Recommendsthe transfer of the historic observations onto modern media by digital techniques, which will provide worldwide access to the data so as to benefit astronomical research in a way that is well matched to the tools of the researcher in the future.CfA/PSSG, 2002-11-18A Half-Million PlatesCfA/PSSG, 2002-11-18Phase 0 (2002): Test scanners CfA/PSSG, 2002-11-18CreoScitex EverSmart $35,000-$50,000 High resolution (4800 dpi), but crashed a lot 20 minutes per scanPhase 0 (2002): Test scanners UMAX PowerLook 3000 $5,000 Adequate resolution (1200 dpi), reliable Under 10 minutes per scanCfA/PSSG, 2002-11-18Phase 0: What we learned● Plate astrometry using FITS WCS is good enough for source ID, but higher order terms needed.● 1200 dpi is enough for most of the sky, but 2400 dpi is better for crowded star fields.CfA/PSSG, 2002-11-18Phase 1:Can science be done with digitized plates? Verify photometry possible with scans of known sequence in galactic star cluster M44CfA/PSSG, 2002-11-18Phase 1:Can science be done with digitized plates?Photometry of known sequence in galactic star cluster M44 on 1947 MC series plateCfA/PSSG, 2002-11-18Phase 1:Can science be done with digitized plates?Photometry of known sequence in galactic star cluster M44 on 1905 AC series plateCfA/PSSG, 2002-11-18Phase 1: Can science be done with digitized plates?Scan multiple plates and study Cepheid variabilityCfA/PSSG, 2002-11-18Phase 2: Improve accessMove the catalog out of the XIXth centuryCfA/PSSG, 2002-11-18Phase 2: Improve accessMove the catalog into the 21st centuryCfA/PSSG, 2002-11-18Phase 2: Improve accessMove the catalog into the 21st centuryCfA/PSSG, 2002-11-18Phase 3: Improve access to imagesMove the plates out of the 20th centuryCfA/PSSG, 2002-11-18Phase 3: Improve access to imagesMove the plates into the 21st centuryUserStack Catalog searchFITS or TiffImage Archive(100 Terabyte)FITS Header Archive(WCS information)FITS extractorObject or coordinates and timePlate names and object (x,y)FITS imagesof plate portionsCfA/PSSG, 2002-11-18Scan PlateExtractStar CentersAdd Photometryand AstrometryMergeFit World CoordinateSystem (WCS)Add Positionand TimeWeb InterfacePlate Scanning PipelinePlate StackCatalogMasterCatalogFITSFileScannedImage


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