3 The catalog

The final catalog (Table 5) contains positions and proper motions for approximately 2400 stars which have been selected with the following criteria: (1) the star must appear in at least 4 of the contributing catalogs, and (2) the maximum epoch difference must be at least 40 years. A photographic magnitude is also given for every object. In the case of the photographic sources the image sizes or total pixel counts were calibrated using the magnitudes in the PPM catalog, and extrapolated to fainter magnitudes. Spectral types are also given, taken from any of the sources. For the determination of the final data weights are given to each of the contributing catalogs according to the average respective mean errors. The contents of the catalogue are as follows:

$$\begin{array} {lp{0.9\linewidth}} \noalign{\smallskip} {1}... ... {18} & ($C$) number of contributing catalogs. \\ \end{array}$$

The average mean errors of the proper motions, both in right ascension and declination, are 0.003 arcsec/year if there are at least 4 contributors, going down to 0.0005 arcsec/year if there are 7 or more contributors. A proper motions error analysis is given in Table 4. A comparison of our catalog with the Hipparcos data, both positions and proper motions, show no systematic pattern. Thus our catalog can be considered to be on the system defined by Hipparcos.

  

Table 4: Proper motion error analysis of the catalogue

$$\tiny \begin{tabular} {\vert c\vert r\vert c\vert c\vert c\... ...oalign{\smallskip} \hline \noalign{\smallskip} \end{tabular}$$

Acknowledgements

The POSS data used in this work are based on plates of the National Geographic Society Palomar Observatory Sky Survey (NGS-POSS) obtained with the Oschim Telescope of the Mount Palomar Observatory. The NGS-POSS is funded by the National Geographic Society of the California Institute of Technology. The Digitized Sky Survey was carried out at the Space Telescope Science Institute, Baltimore, funded by the National Science Foundation under the contract NAC W-2166. We also thank J. Stock for his collaboration during the elaboration of this paper.