What is the farthest point of light that is emitted by a torch? If I focus my torch into the night sky,what would be the farthest point the light can reach? Recently I looked at the night sky and noticed a light spark moving around the clouds for about 15 min.After observation I jumped into a conclusion that its probably because of the light house near by or any powerful light emitter.
If you point a flashlight up, then the light will reach as far as the other ends of the universe, if one has a sensitive enough measuring device, so long as it is not absorbed. Of course, said device might require a lot of work, and a huge telescope. Lights can easily be seen by satellites, but it would take a huge telescope to see a single light from, say, the Moon, and even larger the further you go.

In the case of your moving light, I would suspect a laser of some kind. Lasers are focused enough where one could easily see a reflection from the clouds, and pretty focused as well. It could be a moving light source, such as a plane or balloon of some kind as well.