C2A can read the NOMAD catalogue (Naval Observatory Merged Astrometric Dataset). This catalogue was created in 2005, and combines the Hipparcos, Tycho-2, UCAC2, USNO-B1.0 et 2MASS catalogues. It contains 1,117,612,732 objects (more than a billion!) down to magnitude 21, which represents about 80 gigabytes of data.
Note that C2A can read the complete NOMAD catalogue as well as its reduced version. Moreover, it is not necessary to compile the NOMAD catalogue. C2A directly reads the native format.
You select this catalogue as the current catalogue through the Stars tab of the Options dialogue box, or by SHIFT-right-clicking on the map. You can choose to display either of the magnitude bands B, V, R, J, H or K by clicking the Advanced options... button on the Stars tab of the Options dialogue box.
The information associated with each star in the catalogue is as follows:
- the magnitude in
the bands B, V, R, J, H and K when they exist,
- the right ascension for the epoch 2000,
- the declination for the epoch 2000,
- position errors,
- the proper motion,
- errors on the
proper motion,
- a set of flags specific to the NOMAD catalogue