The Second Palomar Observatory Sky Survey (POSS II)


The 48 inch Oschin Schmidt Telescope at the Palomar Observatory.
(Photograph by R. Danner and D. Hogg)


The first Palomar Observatory Sky Survey (POSS I) was carried out on the Oschin Schmidt Telescope in 1950-57 using 103aO and 103aF plates. POSS I continues to be one of the most frequently used astronomical resources; paper or glass copies of the plates are to be found in most of the world's observatories and a digitized version is available on line from the Space Telescope Science Institute.

During the 1970's finer grain, fast emulsions became available from the Kodak Corporation. The U.K. Schmidt (which is a virtual copy of the Oschin Schmidt, but with an achromatic corrector) carried out a Southern Sky Survey using IIIaJ and IIIaF plates. In the early 1980's it was decided to upgrade the Oschin Schmidt by installing an achromatic corrector and provision for autoguiding. POSS II was designed as a northern complement to the U.K. Schmidt survey using 897 plates in each of three wavebands on IIIaJ (blue), IIIaF (red) and IVN (near infrared) plates, respectively. Substantial funds for the telescope upgrade and the execution of POSS II were donated by the Alfred P. Sloan Foundation, the National Geographic Society and through a series of grants from the National Science Foundation. The Eastman Kodak corporation has provided all of the plates for POSS II in addition to a cash grant.

Several astronomers have contributed to the completion of POSS II, including G. Neugebauer and W. Sargent who were the Principal Investigators on the original grant proposals, R. Brucato who organized the day to day operation throughout the survey, and I. N. Reid who, as Project Scientist, was responsible for monitoring the quality of the plates. J. Schombert was a Postdoctoral Fellow during the early years of the project and J.Mould was also involved in initiating POSS II.

The work at Palomar was carried out by a team headed by Mountain Superintendent R. Thicksten. Palomar Chief Engineer H. Petrie supervised the telescope improvements. A. Maury came from France for 5 years to establish the photographic procedures. The observers included C. Brewer, D. Griffiths, W. McKinley, D. Mendenhall, K. Rykoski, J. Phinney and J. Mueller (who discovered over 100 supernovae by comparing the POSS I and POSS II plates). Ms Mueller also discovered several comets during the course of POSS II and the bright Comet Wilson 1986 was discovered by then graduate student C. Wilson (now at McMaster University) early in the survey.

A detailed account of the aims and methods of POSS II is given in the paper by Reid et al. 1991, PASP, 103, 661.

Glass and film copies of POSS II have been made available to the astronomical comunity through the combined efforts of the European Southern Observatory and the Royal Observatory, Edinburgh. A digitized version of POSS II has been produced by STScI. The POSS II plates are also being digitized as part of the Precision Measuring Machine Project (PMM) by D. Monet of the U.S. Naval Observatory in Flagstaff, Arizona who is preparing a catalogue of 100 million stellar proper motions by comparing the positions of stars on the POSS I and POSS II plates.

A team headed by by S. Djorgovski used the digitized plates from STScI to create DPOSS, a catalogue of objects based on the digital scans of POSS II carried out at STScI.

POSS II formed the basis for the Caltech Ph.D. theses of C. Tinney (Stellar luminosity function at the faint end), N. Weir (artificial intelligence applied to galaxy classification), A. Picard (Galaxy counts), J. Kennefick (high redshift quasar luminosity function), J. Gizis (Population II luminosity function) and R. Gal (distribution of clusters of galaxies).

By the end of 1999 all 897 IIIaJ and 897 IIIaF plates of survey quality had been obtained. At the end of the survey, only 11 IVN fields were missing. At this point the Oschin Schmidt Telescope was modified for robotic operation.


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page by Wallace Sargent, last updated 5 May, 2005