Street lights and bad weather are not the only enemies we astronomists have to contend with. There's also a sneaky adversary up there which will only reveal itself when you're looking through a telescope: our atmosphere. Twinkling stars may appear romantic, to us this is usually the sign that the observing night we were looking forward to so much will probably turn out to be very disappointing. Air turbulences, or "seeing" as we like to call them, are caused by the movement of the air mass around and above us, especially when there's high wind or a powerful jet stream around. As invisible as these turbulences may be to the naked eye, when your telescope magnifies 100x it also magnifies the ripples in the air just as much. Especially when you're trying to observe subtle details on a planet or when you're trying to separate an exceptionally close double star, these turbulences will mess up your view up to the point that you'll soon give up and go to bed.
In order to give you an idea how difficult planetary and high-resolution observation is, I've created this small simulation to show you how I really observed Jupiter the other night. Now you'll understand why the Hubble space telescope's so important.