The Center for Astrophysics version of the catalog is in the local binary format and has had the proper motion added from the epoch of observation, 1991.25, to 2000.0. A spectral type has been approximated for each star, based on the B-V, to give an idea of the color from a single parameter. Three magnitudes, B, V, and B-V are included. As of now, only a searchable RA-sorted version of the catalog is being used, as code has not yet been written to extract stars by their numbers. The numbers are the same as the equivalent (or nearest) HST Guide Star, region.number, with an added digit on the end which starts at 1 and increases if there are more than one Tycho star closest to the same Guide Star.
The Tycho Catalogue can be searched by stycho (which calls scat) and plotted by skymap.
The ACT catalog combines positions and photometric data from the Tycho Catalog with proper motions computed using earlier epoch positions from the USNO AC2000, and gives better positions away from the Hipparcos epoch, especially for fainter Tycho stars.