def mc_factors(parameters):
    """
    Determine relative width of chirp mass range to use.  Low mass binaries will
    have narrower chirp mass contours, so the values should be closer to unity,
    whereas high mass binaries will have wider ones, shifting the values away
    from unity.

    In principle these factors should be a function of the PSD, and should vary
    continuously according to the chirp mass.  One could do PE on a number of
    injections, and determine relative scales from that.  For the moment we just
    use hand-chosen numbers.
    """
    if parameters.Mc_det > 15.0:
        min_mc_factor, max_mc_factor = 0.8, 1.4
    else:
        min_mc_factor, max_mc_factor = 0.98, 1.02
    return min_mc_factor, max_mc_factor
