def calc_exposure_time(num_integrations, ramp_time):
    """Calculates exposure time (or photon collection duration as told
    by APT.)

    Parameters
    ----------
    num_integrations : int
        Integrations per exposure.
    ramp_time : float
        Ramp time (in seconds).

    Returns
    -------
    exposure_time : float
        Exposure time (in seconds).
    """

    exposure_time = num_integrations * ramp_time

    return exposure_time