Shifts positions of all stars in a given file by a specified amount. The amount can be specified with the DX= and DY= keywords, or else the program will prompt the user for values. In addition, OFFSET has a new VISTA function. If a buffer is specified with the OFFSET command, a linear plate transformation will be performed from the header cards REF_AX ... in the specified header. These cards are automatically loaded into the header using the REGISTER command, with the LOAD keyword. See REGISTER for more information. If INV is specified, the inverse transformation is done.