A chronograph is a specific type of watch that is used as a stopwatch combined with a display watch. A basic chronograph has an independent sweep second hand; it can be started, stopped, and returned to zero by successive pressure on the stem. More complex chronographs use additional complications and can have multiple independent hands to measure seconds, minutes, hours and even tenths of a second. In addition, many modern chronographs use moveable bezels as tachymeters for rapid calculations of speed or distance. They are often using additional sub dials to display different functions. Louis Moinet invented the chronograph in 1816 for use in tracking astronomical objects.