>>5114113Those calculations assume the observer is at sea level.
From the mountains in the foreground of your picture it was not taken at exactly sea level. When you have a higher altitude, you are looking down toward the horizon. And, because you're looking down, things that would have normally been hidden can peek out from beyond the horizon, allowing you to see much further than that equation would suggest.
Make sure you look up the assumptions that go along with your equation to prevent it being applied to situations where it's meaningless.
