def calc_theoretical_noise_threshold(imax, theoretical_noise_dr):
    """
    Calculates the theoretical noise threshold from the theoretical noise dynamic range
    imax (float): the maximum of the dirty image
    theoretical_noise_dr (float): the theoretical noise dynamic range
    returns (float): the theoretical noise threshold
    """
    theoretical_noise_threshold = imax / theoretical_noise_dr
    return theoretical_noise_threshold
