CATALOG /ALTERNATE

        This option will open the specified source catalog as a second cata-
    log,  only  accessible  through  the  "/ALTERNATE"  options  of commands
    SOURCE, HORIZON, and CONVERT. For instance, a catalog  containing  cali-
    bration  or  pointing sources may be opened as an Alternate Source cata-
    log, while the objects to study are kept in  the  Current  catalog,  en-
    abling easy switching between the two kinds of objects.