The Lone Star Observatory

It may be Oklahoma, but this amateur-built observatory is all Texas.

Air & Space Magazine | Subscribe

(Continued from page 1)

Though amateurs have contributed important discoveries to the field of astronomy, most have no scientific agenda. Rather, they take pleasure in the learning process—studying galaxies, nebulas (gaseous remnants of exploded stars), and star clusters as they read about the objects. And of course they also enjoy what can be spectacularly beautiful sights. “Galaxies sometimes look like little puffs of cotton,” Walker says. “Then you realize what you’re looking at. Those are the things that give me chills.”

Many members, though, do have well-developed observing programs, in which they study, for example, the intricacies of double stars (two stars that orbit each other), variable stars (which change brightness), or distant galaxies. The group’s telescope is easy to use and has precision optics that show most major categories of celestial phenomena in great detail, so users can modify their programs as quickly as their interests change.

Bringing all this about took roughly three years, beginning with the site selection. The members found a dark site adjacent to one used by the Texas Astronomy Club, and they purchased the one-acre plot for $1,000. Construction began in 1988, with each member contributing some form of sweat equity. While some focused on the clubhouse, the rest worked on the concrete base on which the telescope would sit or the design and construction of the dome. “We had 12 well-educated professionals who’ve never built anything in their lives,” Smith says. “The early part became a wonderful learning experience for all of us. I mean, just how do you build a round building with a rotating roof?”

They studied other observatories to get ideas and broke off into teams to research the computer controls, the mount, and the telescope itself. They finally decided on the design that was the easiest to maneuver, provided the most accessible eyepiece position, and gave them the best views: a classical Cassegrain, which uses a large primary mirror and a smaller secondary one that reflects the light back down through a hole in the center of the primary and into an eyepiece.

As the members laid foundations and framed the two buildings, Mueller, an engineer with an oil well pump manufacturer and one of the few knowledgeable about construction, worked out the design for the steel equatorial mount, which has two arms that hold the telescope between them and a base that is polar aligned—oriented parallel to Earth’s rotation axis and angled to match the observatory’s latitude, enabling it to more easily track objects as Earth’s rotation causes them to appear to move across the sky. Then he built it. “We had a lot of extra room in the machine shop at work and some equipment that wasn’t being used,” Mueller recalls, “so I worked from five until 10 every night for a year to do it.”

Meanwhile, Smith and some other members had found a renowned optical engineer, Jerry Brunache, who convinced them that a certain mirror design—24 inches in diameter and shaped to a focal ratio of f/16—would give them magnificent, large-scale images with few optical defects. As Brunache manufactured the mirror, Hudler worked on the computerization, which he had to invent as he went along. He obtained publicly available databases of sky objects to get coordinates for the computer’s aiming software. It works by first determining where the telescope is pointed from the positions of its gears; then, using the coordinates of the object to be studied, it calculates where the telescope needs to go. Hudler worked to get the software to accommodate a variety of variables, from built-in errors within the electrical motors to the flexing of the 17-foot-long telescope as it moves up and down. When the telescope began operation in 1990, he began testing the software by repeatedly selecting a particular star, slewing away from it, then checking to see if the computer could find the object again.

A number of refinements were necessary. “At first I didn’t have a clue about how to correct these things,” says Hudler, sitting cross-legged on the observatory floor and cleaning a telescope that is much smaller—though still one many backyard observers would cherish as their primary instrument—and that serves as a “finder” scope. “But trial and error and a lot of thinking helped me sort it out. When we fixed them, the computer started nailing every object.”

When darkness falls, the user goes to the telescope’s control center, a desktop computer, and selects what he or she wants to observe (using either common names—Ring Nebula, M31, etc.—or numbered catalog designations). The computer sends the telescope slewing to the proper position. A recent upgrade provides precise simulations on the computer screen of the eyepiece view, point-and-click aiming, and detailed information—size, magnitude, distance, composition—about all objects. Then the observer sits on a large, wheeled, stair-step chair to line up with the eyepiece and uses a hand controller to rotate the 20-foot-diameter, 21-foot-high dome so its narrow opening is lined up with the telescope. The controller also adjusts the focus and moves the telescope around without any computer assistance—usually for random cruising around the universe.

At the eyepiece, the images are indeed spectacular: wispy details in cloud-like nebulas, dark lanes in distant galaxies, and stars so faint that they are inaccessible to most telescopes amateurs buy. Globular clusters, in which thousands of densely packed stars appear as tight spheres, show stars resolved straight to the core. We are eager to see what the scope will reveal of Jupiter, Saturn, and Mars, which at this time of the year won’t rise until after 3 a.m.

Each Lone Star member is entitled to sole use of the telescope a certain number of days per year. The rest of the evenings, such as this one, are open to everyone. The members often bring up school classes or scout troops, or individual young people interested in astronomy. This evening the members alternate at the eyepiece, taking time to discuss what they’re seeing and what might be an interesting next target. When not at the eyepiece, they stretch out on recliners on the observatory’s deck to enjoy the sky and chat. “I’ve always marveled that we were able to put this thing together without much disagreement,” Hudler notes. “Nerves got frayed a couple of times, but decorum was kept at a professional level.”

Comment on this Story

comments powered by Disqus