When I lived SW of Carrizzo, New Mexico in 1954, the visabiliity to the top of a 12,003 foot mountan was about 60 miles. I think, less from the top of the mountain to the 4000 foot plain. I got to use a quality telescope for missile tracking and could just barely see cars moving on route 54 about 7 miles away. Most of the difficulty was the distortion produced by the hot air rising from the desert. Few locations have clearer air. Neil