Fort Davis, Texas: The mind-bending McDonald Observatory


The view from Mt. Locke

“I am made of the dust of the stars, and the oceans flow in my veins.”  —Rush, “Presto”


One of the best observatories in the world is McDonald Observatory, run by the University of Texas at Austin, my alma mater (hook ‘em!).  It’s situated on a few mountain tops in the Davis Mountains of West Texas.  McDonald Observatory is a mind-bending place to visit–-so many great minds accumulated in one place, researching our vast universe, completing all that advanced math….

This was our third trip to the observatory, and as always, it was overwhelming, but in a good way.

Even though the primary purpose of McDonald University is, of course, research, education is also a high priority.  The public outreach coordinators want everyone to get excited about science and astronomy.  The observatory offers several programs for visitors, including a Solar Viewing Program and tour of two of the facility’s most important telescopes, which takes place during the day, and then the nighttime Star Party, which is just as awesome as it sounds (more below).

The Visitors Center, where we checked in for all of our programs; the Harlan J. Smith and Otto Struve Telescopes can be seen on the mountain in the background

We participated in both of these programs and learned so much that it would be impossible for me to share all of it with you, but here’s a sampling of what a visit to the observatory offers:

History of the University of Texas McDonald Observatory

William Johnson McDonald, a lawyer and banker from Paris, Texas, loved astronomy, and when he died in 1926, he donated a million dollars to the University of Texas to develop an observatory.  He had no children, but his extended family contested the will.  After arbitration, the university still received the bulk of McDonald’s gift–over $800,000–and the process of building an observatory began.

There was another problem, however: UT didn’t have an astronomy department.  They turned to the University of Chicago, the top astronomy program in the nation at that time, and the two partnered in developing the observatory.  The University of Chicago ran the facility for the first 25 years, and when their contract ran out, UT assumed responsibility.

The observatory was built atop Mt. Locke, 6800 feet above sea level.  The Davis Mountains were chosen as the location of the observatory for several reasons: it’s far from any large cities and has some of the darkest night skies in the country.  Also, about 2/3 of the nights are clear.  The high elevation was a bonus, and the southern skies can be viewed from this latitude.


The 82-inch telescope built by the observatory was the second largest in the world at that time.  The dome encompassed not just the telescope but the entire observatory, including living and sleeping quarters for the astronomers.  The telescope has been in use since 1939 and continues to be used today. Unnamed for many years, it was dedicated in 1966 to Otto Struve, the first director of the observatory.

The Otto Struve Telescope dome

Today, McDonald has numerous telescopes and a large staff.  Our tour guide said that 70 people live on the grounds (comprising the third largest settlement in Jeff Davis county), and this includes astronomers and technicians who keep the telescopes in perfect condition as well as a full-time meteorologist.  Many of the researchers are from the University of Texas, but astronomers from all over the world come to McDonald.  In order to obtain telescope time, scientists have to submit a request that goes through a committee process; once their project is approved they are given access to the telescopes.

A view of the visitors center and portion of the observatory campus

The Solar Viewing Program

The Solar Viewing Program lasted about 45 minutes.  Our docent, Dan Gordon, first gave a short lecture about the sun, and here are a few fascinating facts about our favorite star:

  • While we of course regard our sun as something special, it is in fact just one of many trillions of stars in the universe.  And it’s not even all that big–-it’s a medium-sized star.
  • We don’t see sunlight in real time–-it takes light from the sun eight minutes and 20 seconds to reach Earth.
  • The sun came into being about 4.6 billion years ago, formed by the gravitational collapse of a gas and dust cloud.  The material at the center of the cloud was compressed so compactly that it ignited a nuclear fusion and produced our sun.
  • Like all stars, the sun is a powerful nuclear fusion reactor at its core.  Most of the energy that makes its way from the core to the surface is released in the form of light, and that’s how we get sunlight.
  • The sun is 27 million degrees Fahrenheit at its core and between 9000-10,000 degrees F. on its surface.

After the mini-lecture, we watched fascinating footage of solar phenomenon.  If the day had been cloud-free, we would have seen live telescope images; however, since it was a cloudy afternoon, we watched recorded footage.  We saw sunspots, solar flarescoronal mass ejections, and hedgerow prominences, among other phenomenon.

Dan said some people believe that the occurrence of certain phenomena, such as coronal holes, indicate that the sun is possibly disintegrating, but he offered some reassurance:  yes, the sun is volatile, and yes, as it nears the end of its life, it will grow into a red giant and quite possibly consume the Earth, but there are no signs that it is going to implode anytime soon.  It has been this way for 4 1/2 billion years and should burn for another five billion years or so.  Whew!

The telescopes

Immediately following the Solar Viewing, Dan took us on a two-hour tour of two of McDonald’s largest telescopes, the Harlan J. Smith and the Hobby-Eberly.

The observatory describes telescopes as “windows to the universe,” which I thought was both poetic and precise.  Astronomers use telescopes to study not only our own solar system but also galaxies that are millions of light years away, and their research digs into the very origins of the universe.

A view of one of the smaller telescopes on the McDonald Observatory campus

Most research these days uses spectroscopy rather than visual astronomy (i.e., peering through an actual telescope).  The telescope captures light from stars or galaxies or whatever the target is; it is then broken down into its spectrum of colors by instruments attached to the scope.  According to an introductory video that we watched, studying an item using spectroscopy is like reading a bar code, the spectrum being the bar code.  Different colors = different elements, and if you know from what elements an object is made, you can gain all kinds of information about that object, including temperature, mass, and composition.  (NASA gives a much better explanation of spectroscopy here).

The Harlan J. Smith Telescope
Harlan J. Smith Telescope

Harlan J. Smith (1924-1991) was director of McDonald Observatory from 1963 to 1989.  He took over management of the observatory at a time when the Space Age was in full swing, and he saw an opportunity to get McDonald involved.  NASA wanted the means to survey our solar system for potential future exploration, and Smith convinced them to build a telescope at the observatory.  NASA co-funded the telescope (which would later be named after Smith). Construction was completed in 1968, and NASA used it for decades for planetary study and for a project called Lunar Laser Ranging.



The Smith Telescope weighs 320,000 pounds and has a length of 32 feet, and at the time it was built it was the third-largest telescope in the world.

The bigger the mirror, the more light that can be gathered; the Smith mirror, 107 inches wide and weighing in at 7800 pounds, gives the telescope a light-gathering power that is up to one million times greater than the unaided eye. Today the telescope is used to further map our solar system and to study distant stars and galaxies.

Our docent, Dan, explaining the mechanics of the Smith Telescope

The telescope is used every clear night of the year.  The mirrors on older telescopes (such as Smith’s) are subject to contracture and expansion, so every effort is made to equalize the temperature within the dome.  In order to minimize the telescope’s exposure to humidity and temperature changes, the dome is opened only at night, and temperature inside the dome matches that which is projected for the coming night.

The base of the Smith Telescope; various instruments can be attached to the scope depending upon the research project being done.
The Hobby-Eberly Telescope (HET)
The Hobby-Eberly Telescope

The Hobby-Eberly Telescope (HET) came out of a joint project in the 1990’s between UT-Austin, Penn State University, and two German universities: Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.  It sits atop Mount Fowlkes (elevation: 6640 feet).   The HET is currently the third largest telescope in the world.

A view of the HET from Mt Locke

The HET was designed specifically to use spectroscopy and is completely data-driven, with no capacity for visual astronomy. Astronomers look at data and numbers, and no visual images are produced.

A modern, traditionally constructed telescope that has the capacity of the HET would cost billions of dollars, and no university has that kind of money, so designers of the HET had to come up with a different way to engineer it, and they succeeded:

In your average telescope, the primary mirror consists of a single piece of glass; however, the Hobby-Eberly mirror is made up of 91 identical hexagonal segments that fit together like floor tiles, allowing for the creation of an immense mirror at a much lower cost.  The segments are also made out of a special glass ceramic that doesn’t expand or contract like traditional glass.

Another innovative and cost-saving feature: instead of tilting up and down like most telescopes, the HET is always angled at 55 degrees above the horizon.   The tracker mounted to the telescope moves in six directions, and this makes it possible for users of the HET to study 70% of the visible sky at any one time (still a significant amount of space).  Because any one area of the sky is visible for only a short period, time is of the essence, so rather than training various scientists to use the HET, the telescope has a dedicated staff of four resident astronomers and four assistants.  No one else is allowed to touch it!

The HET’s mirror can be seen in the lower half of the picture. It’s difficult to see where the mirror ends and the dome’s ceiling begins

The HET is taking part in a ground-breaking study called HETDEX (Hobby-Eberly Telescope Dark Energy Experiment).  In the 1990’s, astronomers discovered the existence of a “dark energy” that comprises approximately 70% of all the matter and energy in the universe.  This mysterious force is causing the universe to expand as it ages (rather than contracting, as would be expected).  HETDEX research is trying to shed light on the composition of dark energy and its impact on the universe.  Fascinating stuff.

Part of the instrumentation being used in the HETDEX experiment

The Star Party

We returned to McDonald Observatory at about 9:30 that night for their most popular program, the Star Party.  I heard one little girl ask her mother, “Will this party have dancing?”  There was no dancing, but it was still quite an event.

First, we gathered in an outdoor seating area for a review of the night sky.  This gave our eyes time to adjust to the dark, as it takes about 45 minutes to fully develop night vision.  Cell phones, flashlights, and photography were forbidden.  As our eyes adjusted, a very entertaining staff member pointed out various constellations, planets, and stars, including:

  • Proxima Centauri, which, excepting our sun, is the star nearest to us.  The light from Proxima Centauri takes 4 1/2 years to reach us.  With current technology, it would take a rocket launched from earth 25,000 years to reach Proxima Centauri!
  • The Milky Way, which is actually a collective glow from stars, dust, and gas.
  • The Hubble telescope and an iridium satellite, both of which were cruising within view across the night sky at high speed.
  • Arcturus, one of the brightest stars seen from earth.  The light from Arcturus takes 40 years to reach us; in other words, the light we were seeing at 10:00 that Saturday night was 40 years old!

After about 45 minutes of exploring the sky, it was time to head to the telescopes.  Staff had set up several different stations trained on the following targets:

Which was our favorite?  Everything was fantastic.  The moon is always amazing to see up close, and Saturn, with its rings, was beautiful, as was the ring nebula.  Mars was merely a hazy red spot and not very impressive, and, unfortunately, Jupiter was lost to us—the lines for seeing this planet were long, and by the time we got to the front of the queue, the view was obstructed by clouds.  Overall, though, we had a wonderful experience.

Note that Star Parties are held regardless of weather every Tuesday, Friday, and Saturday, but if the sky is cloudy or weather is inclement, the party moves indoors and the itinerary is altered.  This happened to us on one of our previous visits.  Instead of looking at live views of constellations and planets, we participated in demonstrations and lectures.  While we were initially disappointed that we wouldn’t be outside under the stars, it turned out to be a lot of fun and an excellent learning experience.

Conclusion: Our place in the universe

There are an estimated 125 billion galaxies in the universe containing a trillion, trillion stars.  Scientists estimate that there are more stars in space than there are grains of sand on all of planet Earth’s beaches.

Thinking about the enormity of the universe can make one feel mighty small, and a visit to McDonald Observatory always makes us contemplate where we fit.  But Dan, our docent, pointed out something rather profound: we are made of the same matter as the stars themselves—oxygen, carbon, hydrogen, and so on.  We may be tiny, but we are literally a part of the universe, not separate from it; we are not insignificant.

And, as Dan also pointed out, scientific research is critical because “the more we learn about the universe, the more we learn about our place in the universe.” (Dan was pretty darned wise).  McDonald Observatory is not just compiling cold, hard numbers about distant places from which we are far removed; with each new fact discovered, we learn something about ourselves as well.



Links to websites provided by McDonald Observatory:

A McDonald Observatory program that I didn’t have time to get into is The Dark Skies Initiative.  We’re being “robbed” of the night sky by light pollution, which is noxious to our health and sleep patterns, wasteful to the tune of billions of dollars a year, and a significant contributor to greenhouse gases and global warming.  Check out the The Dark Skies Initiative and International Dark Sky Association, which offer suggestions for reducing light pollution both at home and in the community.

McDonald Observatory and Department of Astronomy

Star Date Online, McDonald Observatory educational site

Hubble Space Telescope Images


Satellite visibility site

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Solar activity

Real-Time Weather Data

National Weather Service