I had a telescope with me sometime ago near the sea, and although I mostly used it to watch nightsky, I sometimes looked at the other side of the gulf, and guess what, I didnt see any of the ground, only the tower tops. Note that without the telescope I couldnt see a besides a hilltop here and there. Also, I have to note that the sky was pretty clear those days, even saw some fireworks through telescope, but never, ever did I spot the coastline over on the other side of gulf.
That ofcourse is not evidence or proof anyhow, but hey, the FE'ers told me that if you observe you will see the Earth flat. I did, and I found out someone is having illusions or is lying, because I see it curved, like most people do.