McDonald Obs., TX 2013
In June of 2013, I received an educational grant to spend a week at the McDonald Astronomical Observatory in Texas, USA. The McDonald Observatory is located near the unincorporated community of Fort Davis in Jeff Davis County, Texas, United States. The facility is located on Mount Locke in the Davis Mountains of West Texas, with additional facilities on Mount Fowlkes, approximately 1.3 kilometers (0.81 mi) to the northeast. The observatory is part of the University of Texas at Austin.
The McDonald Observatory is equipped with a wide range of instrumentation for imaging and spectroscopy in the optical and infrared spectra, and operates the first lunar laser ranging station. At the of 2013 they were discovering a number of exoplanets. The high and dry peaks of the Davis Mountains make for some of the darkest and clearest night skies in the region and provide excellent conditions for astronomical research.
Pictured above on the left, the Otto Struve Telescope, dedicated in 1939, was the first large telescope built at the observatory. It is located on Mt. Locke at an altitude of 2,070 m.
Not only did it contain the 82-inch (2.1-meter) telescope — then the second-largest in the world — it also housed living and sleeping quarters for the astronomers who used the telescope.
With its heavy steel mounting and black, half-open framework, the Struve is the a beautiful scientific instrument, (pictured above and below). Like other telescopes at McDonald, its mirror is periodically removed and freshly coated with aluminum to maintain its sharp view of the heavens.
Over its more than 80-year history, astronomers have used this telescope to study every type of astronomical object, from distant galaxies to stars in the Milky Way galaxy, to planets, moons, and other bodies of our solar system. It has made some important discoveries, including the discovery of Uranus’ fifth moon Miranda and Neptune’s moon second-largest moon, Nereid. It was used to discover carbon dioxide in the atmosphere of Mars, and methane in the atmosphere of Saturn’s giant moon Titan.
Picture above and found just west of the Struve Telescope, the Harlan J. Smith Telescope is a 107-inch (2.7 m) telescope. Built by Westinghouse for about $5 million, this telescope was then the third largest in the world. Weighing in at 160 tons, it had a fused silica mirror 107 inches (2.7 m) wide that gave it a light-gathering power one-quarter million times greater than the unaided eye. It began regular observations in 1969.
The telescope’s planetary studies played a significant role in preparing for more detailed exploration of the solar system by spacecraft and in understanding the results of those missions. For almost a decade, the telescope also reflected a laser off mirrors left on the Moon by Apollo astronauts, in a program called “lunar laser ranging.” These results have helped refine the distance to the Moon and enabled a better understanding of its interior, and provided a test of Albert Einstein’s theory of General Relativity.
The Harlan J. Smith telescope has been extensively used to study the compositions of stars, the motions of galaxies, and to search for planets around other stars in our galaxy. It continues to be used use every clear night of the year.
The Hobby-Eberly Telescope (HET), dedicated in late 1997, is located on the summit of Mt. Fowlkes at 2,030 m above sea level. It is operated jointly by the University of Texas at Austin, Pennsylvania State University, Ludwig Maximilian University of Munich, and Georg-August University of Göttingen.
Pictured above, with its 11-meter mirror, the Hobby-Eberly Telescope (HET) is one of the world’s largest optical telescopes. It was designed specifically for spectroscopy, the decoding of light from stars and galaxies to study their properties. This makes it ideal in searching for planets around other stars, studying distant galaxies, exploding stars, black holes and more. The telescope is especially suited to conduct large survey projects using spectroscopy.
The telescope’s mirror looks like a honeycomb. It’s made up of 91 hexagonal mirrors. To make good observations, the 91 segments must be aligned exactly, to form a perfect reflecting surface. The mushroom-shaped tower to the side of the HET dome contains a laser-alignment system that works to keep the segments in proper alignment. The mirror segments form a reflecting surface that is 11 by 10 meters. However, the HET is known as a 9.2-meter telescope because that’s how much of the mirror is actually in use at any given time. This makes the HET, scientifically speaking, the third largest telescope in the world.