The objective lens of a refractor is normally built of two elements, one of flint glass, the other of crown glass, figured and sandwiched together to function as a single lens. The combination of two different formulations of glass is an effort to counter or correct chromatic aberration, the varying refraction or bending of light of different colors. Without correction of the aberration, it would be impossible to focus a sharp image of a star.
The flint-glass element for the Lick telescope was cast successfully, but the initial effort at a crown-glass blank cracked when it was packed for shipment. The Feil brothers worked for two years to cast a second satisfactory crown blank and ultimately went into bankruptcy before the elder Feil came back, took charge, and in 1885 shipped a satisfactory disk to be figured for the Lick telescope.
The mounting of the big telescope was entrusted to the firm of Warner & Swasey of Cleveland, Ohio. Worcester Reed Warner and Ambrose Swasey, both born on New England farms, met as apprentices and worked at Pratt and Whitney in Hartford, Connecticut, before starting their own business designing and manufacturing fine machine tools. Swasey’s skills were designing and building machine tools; Warner was a production line expert and amateur telescope maker. Their first effort at a telescope mount, for Beloit College in Wisconsin, proved so successful that a Warner & Swasey mount became the mark of a fine telescope.
They were the high bidders on the mounting for the Lick telescope, but with an obviously superior design that the Lick Trust accepted. The mounting for a large refractor has to hold and point the long, heavy tube of the telescope with exacting precision and move it around a polar axis for east-west motion parallel to the axis of the earth, and a declination axis for north-south motion, so that the telescope follows the apparent movement of celestial objects as the earth turns during the night. The only practical design for a refractor was one that supported the long tube in the middle, which meant that as the telescope rose and fell in altitude from the horizon to the zenith, the eyepiece would swing in a large arc up and down. To allow for the motion the telescope had to be mounted on a tall pedestal, with ladders, a lift, and a movable floor provided to make the working end of the telescope accessible to observers and for the installation of cameras, spectroscopes, and other devices. To achieve the rigidity required for astrophotography with a structure this large was a considerable challenge of machine design and construction.
The third big decision about the telescope was location. This was in some respects the biggest innovation of the project. In a bold move the new observatory was sited not on a university campus in a large city, which had been the norm for telescopes, but on remote Mount Hamilton, a coastal peak near San Jose, far from the loom of light pollution of the cities and high enough for the night atmosphere above the observatory to be still and clear. Carrying the components of a huge, high-precision optical device up the steep paths to the mountaintop proved a greater challenge than anyone had anticipated, and it took longer to finish the observatory than even the pessimists prophesied. Lick died in 1879 without ever seeing the completed instrument that would bear his name. His body was interred beneath the pedestal of the telescope.
The telescope saw first light later that year and was an immediate success. Astronomers from eastern universities, hearing of the number of cloud-free nights, the quality of the seeing, and the light-gathering power of the new telescope, clamored for invitations to the observatory.
Hale heard about the Lick telescope from his mentor Sherburne Burnham in Chicago, but it was not until his honeymoon trip that he had a chance to visit the famed site. Access was by a rugged trail, six hours and 366 hairpin turns by horse-drawn stage from San Jose; the peak, even with the telescope and housing facilities, was bleak. But the skies were all that Burnham had described. Evelina was bored in California, eager to leave after a short visit, and frustrated when Hale extended their stay on the mountain. She didn’t realize that George Hale had found his destiny.
Hale declined an offer to stay and work at Lick. He had already planned a career as an independent astronomer, his father had agreed to build him a private observatory in Chicago, and the equipment had been ordered: an excellent twelve-inch refractor from the fine firm of John Brashear, with a mounting from the same Warner & Swasey shop that had built the mounting for the Lick telescope.
When they returned to Chicago, George and Evelina moved in with George’s mother, now a recluse in her darkened upstairs room. George spent all his time at his new observatory, leaving Evelina to care for his mother. Evelina proposed that they set up housekeeping on their own, but George’s mother wouldn’t hear of it. Other people, she said, would think she had thrown them out.
About the time that George’s Kenwood Observatory was almost finished, William Harper, the president of the new University of Chicago, was taking advantage of the seemingly limitless backing of Rockefeller money to recruit the finest talent in every field to his faculty. He proposed that Hale and his observatory join the University as the nucleus of an astronomy department. Put off by Harper’s aggressiveness, Hale turned down the offer.
Harper could be as stubborn as George Hale. He negotiated with George’s father, and after he persuaded the famed physicist Albert Michelson, the first American recipient of a Nobel Prize in physics, to accept the chair of physics at the new school, he used the prestigious appointment as leverage to strike a deal that would give George Hale a year to evaluate a university appointment before his father gave the Kenwood Observatory and $25,000 to the University of Chicago. A clause of the agreement specified that the University would subsequently raise $250,000 for a larger observatory facility. William Hale was a good enough businessman to expect a proper return on his investments, including those he made in his son’s career.
George was so absorbed in his work at the observatory that he begged off almost all social engagements and other distractions. It was months before Evelina could drag him away for a vacation at Lake Saranac, New York. Even on holiday George couldn’t relax away from his telescope. He finally abandoned the pretense of fly fishing to sneak off to Rochester and a meeting of the American Association for the Advancement of Science. There he overheard Alvan Clark talking about a pair of glass blanks—the largest ever cast—which were in his shop.
Clark explained that shortly after the opening of the Lick Observatory, a group of supporters of the University of Southern California, anxious that Southern California not be outdone by anything in Northern California, had made plans for an even larger telescope. They organized their publicity before their funding and made sure that Scientific American reported that although the new telescope would be only one-ninth greater in diameter than the Lick telescope, its light-grasp would be one-fourth greater and that “the existence of a large city on the moon would readily be detected by the telescope.” They ordered two forty-inch glass blanks from the Paris firm of M. Manto is—there was still no American firm that could pour large glass castings. The blanks were successfully cast and shipped to Alvan Clark, who had built George Hale’s first telescope, to be ground and figured. Warner & Swasey got the contract to build a mounting for the new telescope.
Before Clark began grinding the disks, the crash of 1893 popped the real estate bubble in Southern California. The businessmen who had pledged funds for the telescope decided that they had other priorities more important than beating Northern California in a telescope race, and the huge glass disks, unground and unpaid-for, languished in Alvan Clark’s Massachusetts shop.
Hale excitedly pulled Clark aside. What, he asked, would it take to figure those disks into the objective lens for a large refractor? Clark gave him a rough estimate, and they discussed details of mounting, housing, and siting a telescope that large. From that day Hale was a man possessed. He had always dreamed of bigger and better instruments. Now he would build the biggest and best telescope in the world. He would site it in a fully equipped observatory, with laboratories right on the premises, with instruments like no others that had ev
er been built. All he needed, he calculated, was three hundred thousand dollars.
In the 1890s it was a considerable but not impossible sum. George Hale had grown up with wealth, and he knew there were many men in Chicago who could afford it. The Hale name gave him a ready introduction, and he wasn’t embarrassed to make his pitch for a telescope. For months he made the rounds of offices and homes of Chicago society, proposing his venture to anyone who would listen, his eyes sparkling with enthusiasm as he described his proposed observatory and what it could accomplish for science. Astronomy, he told anyone willing to listen, was ready for a revolution.
Hale did his best to explain that the old astronomy, men looking through telescopes to sketch what they saw, was exhausted. His proposal was something entirely different, an observatory equipped with the most modern laboratories and facilities, darkrooms, and spectroscopes. But no matter how enthusiastic his pitch, he found no takers. Times had changed, potential donors told him. Money was tough, the climate was wrong, this wasn’t the moment. For George Hale it was a good lesson in the vagaries of fund-raising.
Finally, on a tip from a mutual friend, Hale approached the streetcar magnate Charles Tyson Yerkes. Friends called him “Yerkes the Boodler.” The Boodler liked the idea of a telescope with his name on it. When Hale promised that the telescope would be the largest in the world, bigger than the one at the famed Lick Observatory, Yerkes liked the idea enough to call in the press. “Here’s a million dollars,” he was quoted as saying in the Chicago Tribune. “If you want more, say so. You shall have all you need if you’ll only lick the Lick.”
Yerkes’ farsightedness and vision—always good terms for the donor of a telescope—dimmed considerably as the time came around to make good on his commitments. When he realized that the observatory would be at a remote site, and that much of the funding would go to laboratories and other facilities that were far less flashy and less likely to attract favorable publicity than the big telescope, Yerkes balked. Hale, relentless, cajoled Yerkes to follow through on his pledges, pressured contractors to get the work done, negotiated with local and university officials, and mediated between the perfectionists who would fiddle with the lenses and machines forever and the astronomers eager to use their new facility. The strain of the project, especially the battles with Yerkes, took their toll. Hale began suffering recurrent headaches, sometimes bad enough to keep him home in bed.
Friends, noticing his nervousness and anxiety, urged him to go easy. The optician John Brashear, who knew Hale from years of dealings on optical equipment, wrote, “You have a big responsibility on your hands … the only thing I beg you to look out for, don’t overwork yourself. … delegate all the work you can. Save yourself for that—which you can do better than anyone can do for you.”
George Hale was twenty-four years old.
Despite the headaches Hale got the telescope and the observatory built. Yerkes, at what was then a remote site on the shores of Lake Geneva, eighty miles north of Chicago, emerged the most complete observatory in the world. The great forty-inch refractor, with its Clark lenses and Warner & Swasey mounting, was considered a sufficient engineering marvel to be exhibited at the 1892 World Exposition in Chicago.
In spite of routine winter temperatures at the observatory of-20°F, Hale attracted extraordinary optical and astronomical talent to Yerkes. For a period he could boast having the best observers and the best glass grinders in the world together under the domes and in the laboratories. Those who had seen the toll the construction took on George Hale urged him to settle down to the promising career of director of the great observatory. But even before Yerkes was dedicated, George Hale had a new idea.
In his own studies, with solar telescopes, Hale used a spectrograph to study the chemical composition of the sun. By identifying lines in the spectrogram that corresponded to the emission or absorption of particular materials, he could identify the presence of various elements in the sun—almost as accurately as if he had a sample of solar material in a laboratory. Knowing the chemical composition of the sun and the solar atmosphere, astronomers could begin to ask what chemical or atomic processes were at work to create energy and light. What, Hale asked, if the same techniques that he applied to the sun could be applied to distant stars? It would be a whole new field, astrophysics, a discipline devoted to trying to determine what the stars and other celestial bodies outside our solar system were made of and what processes created the enormous energy in them. Once astronomers and physicists made some headway on those questions, they could take on the even grander field of cosmology, which tried to understand how the universe was put together, to discern the size, shape, structure, and origin of the cosmos.
The answers to those questions would demand telescopes far more powerful than even the great Lick and Yerkes instruments. Hale’s new dream was a huge new telescope, somewhere out in the clear air of California, where cloudless mountaintop skies provided night after night of good seeing, and where a facility could be all but immune to light pollution from urban illumination. The telescope Hale had in mind would not only be even bigger than the great Yerkes, but it would turn the circle from refractors, like the Lick and Yerkes telescopes, back to reflectors, like the telescope Newton had once used, relying on a mirror instead of a lens to gather and focus the faint light from distant objects.
The technology of refractors was temporarily exhausted. It might have been possible to cast and grind larger glass lenses than the forty-inch-diameter disks in the Yerkes refractor, but the sheer weight and fragility of the enormous glass disks, which can be supported only at the edges, and the engineering of the long tube, which must rigidly hold and point the lenses, had reached their limits. In France a refractor with lenses close to sixty inches in diameter was built and displayed at the Paris Exhibition of 1900, but it was not successful as a telescope. Even if a bigger refractor could be built, a reflector had many arguments in its favor for astrophysics research.
The light of a star or other distant object goes through the objective lens of a refractor. Because light of various colors bends, or refracts, differently as it goes through the glass, a refractor is not achromatic; the lens forms a series of images of different wavelengths. Only some of these effects can be corrected. A reflector, by using the surface of a mirror to focus the light, avoids this problem. The optics of a big reflector are also easier to grind and polish. Instead of four surfaces of glass to grind, figure, and polish, two on each of the elements that are sandwiched to make up an objective lens, a reflector requires only a single optical surface, the face of the primary mirror.
Finally, the physical mounting of a refractor, with its long, rigid tube supporting the objective lens at one end and an eyepiece or instrument at the other, presents difficult engineering problems as the instrument gets larger. The long tube must be balanced on its equatorial mounting, and for the telescope to reach all areas of the sky, the mounting must be on a tall pillar. When the telescope is pointed toward targets of low altitude, the eyepiece is high off the floor, out of reach of the observer or his cameras. At Lick and Yerkes this problem was solved by having the entire floor of the observatory rise and fall around the fixed telescope mounting pillar. An early accident with the moving floor was another hint that refractors were approaching their technical limits.
Because the light can be bounced back up the tube from the primary mirror to a secondary mirror, in effect folding the focal path of the telescope, a reflector can be built with a relatively short tube, short enough in most instances for the telescope to be mounted in a movable fork with its pivot point close to the primary mirror. Without the weight of a heavy lens to support at the far end of the tube, the reflector can use an open tube, resulting in a lighter structure and greatly simplifying the construction of the instrument.
The reflector is also more versatile than a refractor. The eyepiece, or more typically for a large instrument, the cameras or spectrograph, of a reflector can be mounted at one side of the high end of the
tube, in what is called the Newtonian position, after Newton’s early design. The light from the primary mirror is deflected to the Newtonian focus with a small diagonal mirror suspended inside the telescope. It is also possible to bounce the light from a secondary mirror back through a hole in the center of the main mirror so that cameras and other instruments can be mounted at the base, or supported end of the tube at what is known as the Cassegrain focus. With additional mirrors, the light can be directed to a fixed Coudé position of extreme focal length in a separate temperature and humidity-controlled room. Finally, if the telescope is big enough, the light can be deflected through the hubs of the declination axis, to Nasmyth foci on either side of the telescope. The different foci, each with different focal lengths, add up to increased versatility for the reflector.
When George Hale began thinking about a new telescope, the arguments for a reflector weren’t only theoretical. In 1895, the same year that the lenses for the great refractor at Yerkes were finally finished, Edward Crossley of Halifax, England, presented the thirty-six-inch Calver-Common reflector to the Lick Observatory. The new reflector was overshadowed in publicity by the larger telescope at Yerkes. While Yerkes’ telescope dominated the press, the mirror of what came to be known as the Crossley reflector was quietly refigured and a new mounting built for photographic work. Keeler, the director of the Lick Observatory, used the Crossley, the first large reflector in the United States, to reveal an immense number of spiral nebulae that had never before been recorded.
The Perfect Machine Page 5