POSS2 (A0): Second Palomar Sky Survey (POSS II) field boundaries (19911106)
FILE: poss2.a0
CONTENTS: Second Palomar Sky Survey Field Boundaries
DATASET: This file is part of HyperSky dataset A-1.2, version 19911106. Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: This datafile contains the approximate boundaries for each field in the second Palomar Sky Survey, whose fields cover the sky from the north celestial pole to the celestial equator. The second Palomar survey fields were designed to duplicate the southern sky coverage of the Australian ESO/SERC southern survey, which covers the southern sky from the south celestial pole to the celestial equator.
Both the second Palomar survey and the ESO/SERC survey contain 894 fields, each 6.4 degrees square. The fields are arranged in overlapping bands, centered on even 5-degree declinations extending from the poles to the celestial equator. Fields in each survey are numbered from 1 (at each pole) to 894 (in the equatorial band). Fields 823-894 straddle the celestial equator, and thus are duplicated in the two surveys. Otherwise, the two surveys are essentially mirror images of each other: for any given field number, the field center is the same in each survey except for the sign of the declination.
The field sizes of the first Palomar survey are also 6.4-degrees square. However, the second Palomar survey field centers are somewhat closer together, allowing more field overlap than is provided by the first survey. Also, the second survey's 1950 field center equinox is more recent than the first survey's 1855 equinox. For both of these reasons there is not a one-to-one correspondence between first and second Palomar survey fields. Note also that the first Palomar survey does not stop at the celestial equator, but extends further south, unlike POSS II.
DATA:
The following example illustrates the general format of a typical POSS II survey field description:
Field 489 (06 14 +25)
The field number, 489, is followed by the equinox 1950 field center in parentheses, where the first two values represent the RA in hours and minutes, and the third signed number represents the Declination in degrees.