Importing CDS catalogues

A large collection of astronomical catalogues are available on-line at the Centre de Données astronomiques de Strasbourg (CDS) and can be retrieved by anonymous ftp (see Section ). Most of these catalogues are available in two formats: FITS tables and simple ASCII text files. The recommended route to access these catalogues with CURSA is to retrieve the simple text file version. It is then usually possible to automatically construct an STL description of the file which correctly interprets the celestial coordinates in the catalogue. (If you retrieve the FITS table version the individual sexagesimal components of the celestial coordinates will be treated as separate columns, making the coordinates difficult to process.)

Each CDS catalogue usually comprises (at least¹⁴) two files: the data file containing the columns and rows of the catalogue and a `CDS description file' detailing the contents of the catalogue. By convention this CDS description file has the file name `ReadMe' (and consequently is known as the `ReadMe file'). The description of the catalogue which it contains is in a standardised form. CURSA application catcdsin will read a CDS ReadMe file and construct an equivalent CURSA STL description file from it. This STL description file will usually contain a description of the celestial coordinates in the catalogues which is fully compatible with CURSA.

catcdsin does not copy the CDS catalogue. It merely constructs an STL description file from the CDS description file. Both these files describe (using a different syntax, of course) the same catalogue text file. Because catcdsin does not have to copy the catalogue it executes quickly, irrespective of the size of the catalogue.