TUI supports the following offsets: . Object Arc offset by a given amount on the sky (i.e. along the arc of a great circle). ... Arc offsets are useful for moving a different portion of your object or a different nearby object onto the boresight . ... Object Arc XY this is identical to an Object offset except that it has been rotated to align along the instrument x-y axes. ... This is just like the Calibration XY offset, except that it is typically cleared when you slew to a new object. ...