C2A is delivered with the Smithsonian Astrophysical Observatory Star Catalogue which is a catalogue of stars down to magnitude 11.9. It contains 258,997 objects. You select this as the current catalogue through the Stars tab of the Options dialogue box, or by SHIFT-right-clicking on the map. The information associated with each star is as follows:
- the star’s catalogue number;
- the visual magnitude;
- the spectral type of the star which is represented by one of the following letters and associated colours: O (blue), B (cyan), A (white), F (light yellow), G (yellow), K (orange), M (light red), C et N (red). The spectral type is generally followed by an integer between 0 and 9. In addition, a special code may be attached to certain objects: W (Wolf-Rayet stars), P (gaseous nebulae), Q (novae). Grey is used to denote stars of unknown type. Turn to the section on Object symbols to see the different types of stars;
- the right ascension for the epoch 2000;
- the declination for the epoch 2000.
The brightest stars of the SAO catalogue have additional information attached to them. This gives in particular:
- the Henry Draper catalogue number if it exists;
- the Harvard Revised Number if it exists;
- the complete spectral type of the star given in the Bright Star Catalogue.