“Line of sight” can refer to any line, but I think you mean “eye level” – i.e. a horizontal line from the telescope, perpendicular to the vertical direction at the telescope?
From any given position the water surface is going to seem to “drop” away from the horizontal plane (it’s like you are standing on top of a very large ball). So the middle pole is going to be below that plane, and the distant bridge will be below that.
So if you take a line of sight from the telescope to the distant bridge ... Read even more
