def resolution_eslin(nu):
    """min max spectral resolution for ESLIN 

    Args:
       nu: wavenumber bin

    Returns:
       min, approximate, max of the resolution

    """
    return nu[0]/(nu[1]-nu[0]),((nu[-1]+nu[0])/2.0)/((nu[-1]-nu[0])/len(nu)),nu[-1]/(nu[-1]-nu[-2])