This photo, taken inside the dome from the visitor's gallery, shows the Hale telescope and part of the framework used to hold and position it. At the bottom of the telescope lies a perfectly-polished parabolic mirror that a whopping 200 inches (over 16 feet) in diameter. The mirror began life as a massive Pyrex casting done at the Corning Glass Works in upstate New York. The 40-ton casting was transported across the country by rail, and finally bought to the mountaintop on a trailer pushed and pulled by three diesel trucks. Polishing the mirror to its final desired shape removed 10,000 pounds of glass from the original casting, and took a full thirteen years. The mirror reflects images upward to what's called the prime focus at the top of the telescope. In the early years, astronomers would physically ride in the prime focus cage and look directly through the optics. Today, electronic equipment gathers the image data and feeds it into computers in a nearby room.