POSS (A0): Palomar Sky Survey (+ MCG, CGCG) field bounds (19920620)
FILES: poss_rad.a0, poss_dra.a0
CONTENTS: Palomar Sky Survey Field Boundaries, Includes Whiteoak extension plus field identifications for MCG and CGCG
DATASET: These files are part of HyperSky dataset A-1.1, version 19920620. Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: These datafiles contain the approximate field boundaries for each of the Palomar Sky Survey's 6.4-degree-square charts. Boundaries include the -30 declination zone, which was not initially part of the Palomar Sky Survey, but was later released with it. Boundaries also include the Whiteoak extension to the survey done in the 1950s by J.B. Whiteoak, an Australian radio astronomer. This extension covered southern declination zones -36 and -42, using the same field centers as the corresponding northern declination zones. Unlike the Palomar survey, which consisted of both red and blue plates, the Whiteoak extension consisted of red plates only and is less commonly available.
In addition to the Palomar Sky Survey plate identifications, there are also field identifications for two catalogs based on the Palomar survey. These are the Russian Morphological Catalog of Galaxies (MCG) and the Zwicky Catalog of Galaxies and Clusters of Galaxies (CGCG). These two catalogs refer to the Palomar survey plates using their own field identification schemes, which are included here for cross-reference.
The CGCG extends only from the north pole to the celestial equator, so there are no CGCG references in southern fields. The CGCG also excludes Palomar survey plates north of the celestial equator which are primarily Milky Way fields; such fields are noted in the files with the convention "CGCG ---". Unlike the 6.4-degree Palomar and MCG fields, the CGCG fields are 6 degrees square, and are slightly off-centered from the Palomar plate centers, though they are always wholly contained within the respective Palomar field. As a result, positions near the edge of a particluar Palomar field will occasionally be off the edge of the corresponding CGCG field. This is not a severe problem, however.
The MCG covers the entire Palomar survey, including the Whiteoak extension, down to the -42 zone, though the Whiteoak zones (-36 and -42) are not used extensively. Each MCG field has a two-part identification of the general form AA-BB, where AA (+ or -) is the zone number measured north or south of the celestial equator, and BB is the field number within that zone. These two numbers form the first part of all MCG galaxy names, which have the complete form AA-BB-CCC. In this name AA and BB are as described above, and CCC is the galaxy number within the field (BB).
DATA: The two files POSS_DRA.A0 and POSS_RAD.A0 are identical in content, except for the RA/Dec order of the Palomar field identification. In POSS_DRA.A0 fields are identified with Dec preceding RA; in POSS_RAD.A0 RA precedes Dec. As an example, the field center of the default HyperSky field (in Orion) is identified as follows:
File POSS_DRA.A0: PSS +00 05 36, MCG +00-15, CGCG 396
File POSS_RAD.A0: PSS 05 36 +00, MCG +00-15, CGCG 396
The POSS_DRA.A0 file is provided since the survey plates are typically organized by Declination zone (ie, Dec preceding RA), which some users will prefer. The POSS_RAD.A0 file is provided since other users may prefer the RA - Dec order more commonly used in defining celestial positions. Either way, only one of the two files is needed for a HyperSky session.
Far southern fields are clearly marked by a second line indicating the field is part of the Whiteoak extension. An example follows:
PSS -36 05 36, MCG -06-13
Whiteoak ext.
Note that there is no associated CGCG field id, since the field is well south of the celestial equator and thus not part of the CGCG.
Thanks are extended to Dr. Harold Corwin of the University of Texas at Austin for invaluable discussion and assistance provided in developing this file.