"open horizon" is correct and usable in written English.
You can use it to refer to an expansive, possibly limitless scope of possibilities or events. For example, "Her education enabled her to gain valuable knowledge and experience with an open horizon."
The ocean below me is calm and stretches toward an open horizon.
This is infinitely preferable to a pony with an unquenchable desire for the open horizon; I am perfectly happy.
Here the open horizon of the Midwestern prairie turns inward, as if compressed within the compass of one life spiraling through space and time.
They constitute what Raymond Williams called "the emergent" – and the reason why history is never closed but maintains an open horizon towards the future.
"Conspicuous nonconsumption has become the more prestigious thing, the idea that you don't need a whole bunch of stuff, only the good earth and the open horizon and the chance to rectify your cardiovascular system".
Similar to how baby sea turtles mistake the glow of beachside hotels for the light of the open horizon that hangs over the sea, lights from humans can be distracting (and, in the case of sea turtles, deadly).
But it is their vegetables, cooked low and forever, that can open horizons for anyone seeking to understand what Mr. Brock is trying to do.
With last year's drought not too distant a memory, some residents may be more inclined to value water supplies and open horizons.
"Art is the only way to open horizons in front of your eyes, instead of being bound by inhibitions and prohibitions.
The other, more evanescent elements — the eternally open horizons of Mr. Wilson's blue-lighted backdrops; his twitchy movement vocabulary; Ms. Childs's swirling dances — feel, in the final estimation, dazzling yet dispensable.
Sunny winter days, wide open horizons and acres of groomed ski slopes, all within hours of the city.
