def fovray(inst, raydir, rframe, abcorr, observer, et):
    """
    Determine if a specified ray is within the field-of-view (FOV) of a
    specified instrument at a given time.

    http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/fovray_c.html

    :param inst: Name or ID code string of the instrument.
    :type inst: str
    :param raydir: Ray's direction vector.
    :type raydir: 3-Element Array of floats
    :param rframe: Body-fixed, body-centered frame for target body.
    :type rframe: str
    :param abcorr: Aberration correction flag.
    :type abcorr: str
    :param observer: Name or ID code string of the observer.
    :type observer: str
    :param et: Time of the observation (seconds past J2000).
    :type et: float
    :return: Visibility flag
    :rtype: bool
    """
    inst = stypes.stringToCharP(inst)
    raydir = stypes.toDoubleVector(raydir)
    rframe = stypes.stringToCharP(rframe)
    abcorr = stypes.stringToCharP(abcorr)
    observer = stypes.stringToCharP(observer)
    et = ctypes.c_double(et)
    visible = ctypes.c_int()
    libspice.fovray_c(inst, raydir, rframe, abcorr, observer, ctypes.byref(et),
                      ctypes.byref(visible))
    return bool(visible.value)