The Welsh longbow could fire 700 yards, even. Would be like a composite longbow with the distance ability...
I know driving down I-90 I could pick out cars at 2 & 1/2 miles away on a clear day. My sight is pretty terrible, too.
The horizon, for those who wanna know (hehe) on a flat plain is the square root of twice your height (where you see from) times the radius of the body you're on.
This is easiest to do with kilometers and then convert, because you are generally significantly smaller than your planet.
So, if you're 2 meters tall, on Earth, The horizon is (.002 * 2)^1/2 * 6,300 = about 12.5 km away, or about 8 miles.