Adaptation to open prairies

"Outside the ranch fence, pronghorn sometimes pass in the light. Pronghorn are the world’s fastest mammals over long distances. They can sustain a speed of sixty miles per hour for hours on end; their eyes can see three hundred degrees; they can detect movement four miles away. Pronghorn, Antilocapra americana, are the only surviving species of the Antilocapridae family—and barely. Pronghorn, of which there were roughly thirty-five million in the early nineteenth century, were largely hunted out of existence to feed the European settlers and construction crews that facilitated the westward takeover of the continent. Their habitats were ransacked, their migration routes disarranged, truncated, cut off. By the late twentieth century, only twelve thousand remained: those that outran the extinction, or outsaw it. I believe them to be a miracle."

-- from No Guarantees, an essay in Harper's magazine.

I seem to remember reading that pronghorn are so superbly adapted for distance vision on open prairies that they could look skyward at night and see the moons of Jupiter.  

But Snopes says their 8X vision would not detect the rings of Saturn.

Addendum:  A tip of the blogging cap to reader Vince who provided a link to Astronomy that demonstrates that 8X magnification is sufficient to see the moons of Jupiter.