The McMath solar telescope is the largest solar observatory in the world and operates twenty-four hours a day for daytime solar and nighttime stellar research by staff and visiting scientists. Only part of the telescope stands above ground; the light-beam tunnel and observing rooms are buried under the mountain. At the top is a 2 meter flat mirror mounted in a heliostat that tracks the Sun or stars and directs light 135 meters down the polar axis to a 1.6 meter concave, image-forming mirror. That mirror returns the beam back up the tunnel to a 1.5 meter flat mirror, which sends it into the observing room below. The main beam from the 2 meter mirror produces an image of the Sun about 84 cm in diameter in the main observing room. There, a 13.5 meter vertical spectrograph spreads sunlight into its component colors and enables astronomers from around the world to study the composition, motions, and magnetic fields of the Sun, while a more compact stellar spectrograph is used at night to study stars similar to the Sun. A laboratory east of the telescope building can receive the diverted beam for further study of sunlight, where physicists simulate high-temperature solar gas. Focusing the telescope and setting up the light feeds is done by moving mirrors along railroad tracks in the long tunnel. Two smaller auxiliary telescopes on either side of the main instrument can operate simultaneously, allowing three different astronomers to work at the same time with different instruments. The telescope is named for Robert R. McMath, a Detroit engineer whose lifelong interest in the Sun and in this observatory played a major role in the founding of the observatory on Kitt Peak.