def get_scalebar(inst, ins_mode=None):
    """
   Sets the scalebar of the chart, as a function of the instrument
   
   Args:
      inst (string): the instrument name
   Returns:
      (scl, scll): tuple with the scalebar length (in degrees) and label
   """
    if inst == 'MUSE':
        if ins_mode is None:
            raise Exception('Ouch! For MUSE, I need to know the mode !')
        elif 'NFM' in ins_mode:
            return 1.0 / 3600, '1$^{\\prime\\prime}$'
        else:
            return 20.0 / 3600, '20$^{\\prime\\prime}$'
    elif inst == 'HAWKI':
        return 60.0 / 3600, '1$^{\\prime}$'
    elif inst == 'XSHOOTER':
        return 20.0 / 3600, '20$^{\\prime\\prime}$'
    elif inst == 'ESPRESSO':
        return 5.0 / 3600, '5$^{\\prime\\prime}$'
    else:
        raise Exception('Ouch! Instrument unknown ...')
