Palomar Observatory Sky Survey

Palomar Observatory Sky Survey
Name	Palomar Observatory Sky Survey
Caption	Survey photographic plate from the Hale Telescope
Established	1948–1958
Location	Palomar Observatory, San Diego County, California
Telescope	48-inch Samuel Oschin Telescope
Operator	California Institute of Technology, Palomar Mountain Observatory
Wavelength	Optical (blue and red)
Plates	~1,872 pairs
Status	Completed; digitized successors ongoing

Palomar Observatory Sky Survey is a mid-20th-century photographic sky survey conducted from Palomar Observatory using the 48-inch Samuel Oschin Telescope, producing a complete northern-hemisphere atlas that became foundational for observational programs at institutions such as California Institute of Technology, Jet Propulsion Laboratory, and Mount Wilson Observatory. The survey influenced major projects including Sloan Digital Sky Survey, Two Micron All Sky Survey, Digitized Sky Survey, and follow-on efforts by organizations like NASA and National Science Foundation.

History

The project was initiated by astronomers at California Institute of Technology and funded through collaborations with agencies including U.S. Navy and patrons associated with George Ellery Hale legacy, with observations conducted between 1949 and 1958 from Palomar Mountain. Early planning involved personnel and institutions such as Walter Baade, Adriaan van Maanen, Harlow Shapley, and staff from Mount Wilson Observatory, integrating techniques developed at Lick Observatory and adopted by surveys like Harvard College Observatory patrols. The survey's operational era overlapped with programs like National Geographic Society sponsored expeditions and postwar instrumentation improvements at Jet Propulsion Laboratory and influenced subsequent mapping initiatives including APM Galaxy Survey and Palomar Transit Grism Survey participants.

Instruments and Photographic Plates

Observations used the 48-inch Samuel Oschin Telescope built by engineers associated with Caltech and instrument teams influenced by designs from George W. Ritchey and Henry Norris Russell. Photographic plates employed emulsions from firms connected to Eastman Kodak Company and glass suppliers used by Harvard College Observatory and Royal Observatory Greenwich programs. Each field was captured in paired blue-sensitive and red-sensitive exposures on 14-inch plates that matched plate scales used in contemporaneous surveys at Mount Wilson Observatory and methodologies refined at Yerkes Observatory. The plate archive, stored at Palomar Observatory and later curated by Space Telescope Science Institute, became a key resource for cross-matching with catalogs maintained by Royal Greenwich Observatory and data centers like Centre de Données astronomiques de Strasbourg.

Survey Methodology and Coverage

The survey adopted a systematic tiled strategy covering declinations north of roughly −25 degrees with overlaps patterned after tiling schemes used by Harvard College Observatory and later by Sloan Digital Sky Survey stripes. Observing protocols included exposure times and emulsions coordinated with standards from International Astronomical Union committees and calibration fields tied to photometric sequences established at Mount Wilson Observatory and by Landolt photometric standards. Plate numbering, astrometric reference frames and field overlaps facilitated cross-identification with catalogs such as those produced by Henry Draper Catalogue and influenced astrometry work at United States Naval Observatory. Nightly logistics involved coordination among observers who had trained at institutions including California Institute of Technology and Lick Observatory.

Data Processing and Catalogs

Initial plate inspection, object identification, and hand-measured astrometry were performed using measuring engines similar to those at Harvard College Observatory and cataloging conventions compatible with Henry Draper Catalogue and Bonner Durchmusterung. Subsequent digitization initiatives produced scans used to assemble digital catalogs comparable in intent to Sloan Digital Sky Survey and USNO-B Catalog, enabling cross-matches with infrared surveys like Two Micron All Sky Survey and radio surveys such as NRAO VLA Sky Survey. Processing pipelines at centers including Space Telescope Science Institute, National Optical Astronomy Observatory, and Centre de Données astronomiques de Strasbourg applied algorithms developed by teams with members from Jet Propulsion Laboratory and Caltech. Resulting catalogs underpinned resources like the Digitized Sky Survey and were incorporated into services run by SIMBAD and VizieR.

Scientific Contributions and Discoveries

The survey enabled discovery and characterization of numerous objects studied by researchers affiliated with California Institute of Technology, Harvard-Smithsonian Center for Astrophysics, and Max Planck Institute for Astronomy, including identification of faint galaxies that fed into work by Edwin Hubble successors and galaxy morphology studies advanced by Allan Sandage and John Herschel lineage research. It provided critical pre-imaging for transient follow-up by teams at Palomar Transient Factory and informed optical identifications for radio sources cataloged by NRAO and X-ray sources cataloged by Einstein Observatory. Studies using the plates contributed to proper motion surveys that traced nearby stars in catalogs maintained by United States Naval Observatory and aided supernova progenitor searches pursued by groups at Lawrence Berkeley National Laboratory and University of California, Berkeley. The archive supported gravitational lens candidate searches that later involved researchers at Harvard University and Princeton University.

Successors and Digitization Efforts

Major successors include the Second Palomar Observatory Sky Survey and digital projects such as the Digitized Sky Survey mosaics, supported by collaborations among Space Telescope Science Institute, European Southern Observatory, and National Optical Astronomy Observatory. Digitization and recalibration efforts have been executed by teams from California Institute of Technology, Jet Propulsion Laboratory, and international partners including Max Planck Institute for Astronomy and Royal Observatory, Edinburgh, enabling integration with modern surveys like Sloan Digital Sky Survey, Pan-STARRS, and Gaia. Ongoing curation by archives such as Space Telescope Science Institute and data services like VizieR and SIMBAD continue to make the photographic legacy accessible for contemporary research spanning programs at NASA, European Space Agency, and university observatories worldwide.

Category:Astronomical surveys Category:Palomar Observatory