def calc_obs_efficiency(t_exp, t_duration):
    """Calculates the observation efficiency.

    Parameters
    ----------
    t_exp : float
        Exposure time (in seconds).
    t_duration : float
        Duration time (in seconds).
    
    Returns
    -------
    obs_eff : float
        Observation efficiency.
    """

    obs_eff = t_exp/t_duration
    return obs_eff