Table: The Pointing Grid Catalogue PTGRID.CAT (Equinox 1950.0)
The Pointing Grid Catalogue PTGRID.CAT (Equinox 1950.0)
The Pointing Grid Catalogue PTGRID.CAT (Equinox 1950.0)
The Pointing Grid Catalogue PTGRID.CAT (Equinox 1950.0)
The Pointing Grid Catalogue PTGRID.CAT (Equinox 1950.0)
This grid of pointing stars was compiled by Roger Wood and Janet Sinclair and covers the whole sky north of declination -30. The aim has been to locate stars close to grid points on meridians separated by 1 hour in right ascension and separated by 15 in declination. Thus, for even hours of Right Ascension grid points were taken at Declinations -30, -15, 0, +15, +30, +45, +60, +75, and for odd hours of Right Ascension at Declinations -22.5, -7.5, +7.5, +22.5, +37.5, +52.5, +67.5, +82.5, supplemented by a single point at +90, a total of 193 points. Each star is identified by a catalogue name indicating the position of its nearest grid point in the format RADD.
For the best astrometric accuracy the AGK3 catalogue has been used north of the equator and, since there is no comparable catalogue in the south, the Perth 70 catalogue where suitable stars exist or the SAO catalogue where they do not. In order to create a grid of stars with uniform properties the following selection criteria were adopted:
It was not always possible to apply these criteria rigidly. In difficult cases, the star which seemed to fulfil most of them has been chosen. An overlay was also produced for each field so that the star images could be examined on the Palomar survey prints. For AGK3 stars, the photographic magnitudes given are taken straight from that catalogue. The Perth 70 and SAO catalogues give only visual magnitudes: in consequence the magnitudes given here have been adjusted by applying a nominal B-V derived from the spectral type of the star.