Hobby Eberly Telescope
The HET is one of the world's largest optical telescopes, with an effective aperture of 10 meters and a 78 square meter, hexagonal mirror array made from 91 segments. Its design is revolutionary. It sits at a fixed elevation angle of 55º, and rotates in azimuth to access 81% of the sky visible from McDonald Observatory (discounting the "high airmass" zone right next to the horizon which telescopes normally avoid). The HET was built for approximately 15-20% of the cost of other 9 meter class telescopes. The tilted Arecibo design, and the cost savings realized throughout the mechanical systems of the HET from the fixed axis concept, broke the standard cost paradigm for large aperture telescopes.