Telescopes are always better than eyes. For example, because of the wave nature of the light we can only see the angular size of the Jupiter's width whereas with the help of telescope we can see the Great Red spot of Jupiter. Telescopes can record the observations with cameras. How much ever we draw things that we saw with our eyes, it will never match the observations the camera has saved because it is the fine details. Thus for accurate observations and to share the same to the world Cosmologists use Telescopes.