How far can i see?

John C. Polasek wrote:
It's 1.23 sqrt(h ft)

This looks right: horizon distance in nautical miles is approximately
square root of height in feet. (One nautical mile is about 1.15
statute miles.) If you are looking at an object with finite height,
add the horizon distances for your own viewing height and the object
height.

Of course this is the _geometric_ horizon. The true horizon is
somewhat farther away because of refraction. On the other hand,
viewing conditions are often less than perfect.