def offset(acqu, proc):
    """
    computes the offset from Bruker to spike
    """
    try:
        ppmPointUn = float(proc['$OFFSET'])
        ppmWidth = float(acqu['$SW_h']) / float(acqu['$SFO1'])
        calibrationOffset = float(ppmPointUn - ppmWidth) * float(acqu['$SFO1'])
    except:
        calibrationOffset = 0.0
    return calibrationOffset
