History of Mount Wilson Observatory

Bringing Astronomy to an Isolated Mountaintop

(this article was written by Mike Simmons in 1983 for the Mount Wilson Observatory Association [MWOA])

A few primitive mountaintop cabins set among tall pine trees, hikers exploring the rugged wilderness on foot and horseback, a commanding view of the orchards or a pioneer community in the valley a mile below -- this was the unlikely setting for a revolution in the making, a revolution in science that could alter our understanding of the sun and stars and our place among them. Many fundamental questions would be answered as Mount Wilson developed into the center of the astronomical world in the first decades of the twentieth century. Imagination, innovation, and a rare collection of scientific genius would become hallmarks of the Mount Wilson Observatory, a tradition established at the very beginning by its founder.

George Ellery Hale was born into a wealthy Chicago family on June 29, 1868. In the post-Civil War period the study of astronomy consisted mostly of the measurement of star positions, brightness and motions. The days of the spectroscopic study of the sun and stars' composition, and the consequent need for very large telescopes, lay far in the future. the world's largest telescope (excluding the relatively poor quality speculum metal reflectors, such as Lord Rosse's ``Levithan of Parsontown'') was the 18 1/2-inch Clark reflector of Chicago's Dearborn Observatory.

Four years before Hale's birth, in 1864, Benjamin Wilson had built a trail to the top of a broad mountain, later known as Wilson's Peak, in Southern California's Sierra Madre range. The lumber he sought for use on his ranch in the valley below did not prove suitable, and the trail lay abandoned. The town of Pasadena at the base of the mountain range would not be established for another five years, and the broad expanses of the San Gabriel Valley were broken only by the fences of the great ranchos.

In 1873, a group of families from Indiana started a new community at the base of the mountains on part of Benjamin Wilson's old ranch. The ``Indiana Colony'' quickly grew into the thriving community of Pasadena, and within ten years land values had increased tenfold.

Aside from the occasional explorer or prospector, the mountains above Pasadena attracted little attention. When John Muir climbed to a point near Wilson's Peak in 1877, he described the range as ``more rigidly inaccessible than any other I ever attempted to penetrate.''

Wilson's old trail was soon refurbished, however, and in the 1880's the adventuresome of Pasadena commonly made the difficult 9-mile journey. Wilson's old half-way house served as overnight accommodations, the one-way trip taking two days on horseback.

Meanwhile, George Hale had grown into an extremely industrious and precocious teen-ager. Having become quite proficient with tools his father had supplied, he built his first telescope in the backyard ``laboratory'' he had constructed himself. In later life, Hale would build the world's largest telescope four times, but his first telescope failed to perform well, and soon he bought expert advice. Having noticed a small box-like structure in a neighbor's yard, he was told ``A queer man lives nights in that cheese box and tells fortunes by the stars.'' The ``queer man'' turned out to be the great double star observer S.W. Burnham, who was still working as a court reporter during the day and making his observations as an amateur each night. Burnham told him of a used 4-inch Clark refractor that was available, and his father, recognizing the remarkable talents of the fourteen-year-old, purchased the instrument, starting him on a course of study that would last him his entire life.

Hale spent four years studying at the Massachusetts Institute of Technology, but, although he did well, he found formal course work less interesting than research. Working at Harvard College Observatory as a volunteer assistant, Hale first tested the spectroheliograph, an important instrument he had invented which would later become a valuable tool on the powerful solar telescope at Mount Wilson. After graduation, Hale's father once again helped finance his son's dreams by buying a 12-inch refractor with a Brashear lens and Warner and Swasey mount. This was a suitable instrument to carry the new spectrograph, and Hale now began publishing the results of original research conducted in the new Kenwood Observatory, also provided by his father, located next to the family home. He hired an assistant, Ferdinand Ellerman, who would later become the first astronomer to join Hale at the new observatory at Mount Wilson.

Potential Observatory Site
While Hale was a student, Mount Wilson began to attract attention as a potential observatory site when E.F. Spence, a banker and former mayor of Los Angeles, promised the University of Southern California $50,000 toward the construction of a 40-inch refracting telescope, which would be the world's largest. President Bovard of USC sought advice from Edward Pickering, director of Harvard College Observatory, and suggested that Mount Wilson be considered for a Harvard Observatory station, which would share the mountain with the proposed Spence Observatory. A Harvard expedition led by William Pickering, the director's brother, and including Alvan Clark, the great optician, tested the observing conditions on Mount Wilson in January 1889. Pickering said of Mount Wilson, ``I consider this the point of all others to place the largest and finest telescope in the world.'' By spring, Harvard had installed a Clark 13-inch refractor on the mountaintop. Meanwhile, Bovard, on behalf of USC, ordered the 40-inch telescope from Alvan Clark and Sons.

The hardships suffered by the Harvard astronomers on Mount Wilson were enormous. The winter of 1889-90 was one of the severest on record, with frequent rain and snow ruining delicate instruments. Difficulties developed with the owner of the land leased for the observatory, and the observers were so isolated they complained of being ``practically excluded from the world.'' Visitors to the mountaintop were no help, as observer Robert Black explained in a letter to Pickering describing encounters with tourists from nearby camps: ``This morning a party of them came around the building when we were asleep -- tried to pry open the door and windows -- climbed the dome and hammered the tin, and climaxed the whole affair by moving the slides of the recorder down and piling them on top of each other.''

These difficulties, combined with misunderstandings with USC, led Pickering to abandon the site after just 18 months. The worsening condition of the Southern California economy caused support for the proposed Spence Observatory's 40-inch telescope to all ut disappear. Thus the mountain was abandoned to the hikers, although local interest in astronomy did not disappear; on nearby Echo Mountain an observatory with a 16-inch refractor was built by Professor Thaddeus Lowe in 1894 and remained in operation for 34 years.

New Home for 40-inch
The glass for the 40-inch lens had been ordered by Alvan Clark and Sons before the plans for the telescope dissolved. Hearing that the glass was available, Hale approached President Harper of the University of Chicago with plans of his own. Together they convinced Chicago streetcar magnate Charles Yerkes to donate sufficient funds to complete the telescope and to construct a building for it on Lake Geneva, Wisconsin, near Chicago. The Mount Wilson Toll Road Company wrote to Hale suggesting that the 40-inch be placed on Mount Wilson, as originally planned. Hale replied, perhaps regretfully, that Mount Wilson was ``too far away.'' Remaining in Wisconsin, the 40-inch was completed in 1897.

As the Yerkes Observatory's first director, Hale collected a strong staff, the nucleus of the future Mount Wilson Observatory staff, including Ellerman, Walter Adams and George Ritchey. Adams would later succeed Hale as the director of Mount Wilson Observatory, and Ritchey, who first learned optics at Yerkes, would become famous as the maker of the Mount Wilson 60-inch and 100-inch mirrors.

In 1902, Hale learned that Andrew Carnegie had established the Carnegie Institution of Washington to support original research in all scientific fields. He immediately saw the possibilities for furthering his own lines of research, having determined that new methods were necessary in order to advance our understanding of the sun and stars. Hale felt new telescopes should be designed to suit the problems they are meant to investigate rather than the other way around. Telescopes such as the Lick 36-inch and Yerkes 40-inch refractors, great as they might be for many purposes, were not well-suited to the study of the solar spectrum. The coelostat (in which the majority of the telescope remains stationary and a single mirror tracks the sun) had obvious advantages for the study of the sun. With such an instrument, one could use much larger and more powerful spectroscopes than could be carried by even the largest moving telescopes.

Large Reflectors Needed
Hale also felt the future of stellar spectroscopy would best be served by large reflectors. Refractors had reached their practical size limit with the 40-inch, but more light was needed if the stars' spectra were to be examined in the same detail as the sun's. In 1896, Hale's father had yet made another contribution to his son's career making him a gift of a 60-inch optical glass disc for the mirror of a giant reflecting telescope. Had Hale's father not died soon after, he might have provided funds for the mounting, but as it was the disc lay in the Yerkes Observatory basement while Hale searched vainly for a donor to complete the telescope. He even wrote to Col. Griffith in Los Angeles, who later gave Griffith Park to that city.

Chief among Hale's plans for the future was the furtherance of the ``New Astronomy'', the combination of physics and astronomy which he termed ``astrophysics.'' Astronomy was still primarily involved with describing a star's brightness and motion rather than what it was made of. Hale felt that a physical laboratory as part of an observatory would yield information on spectra that would be invaluable in the study of the physical properties of the sun and stars.

Hale was asked to serve on the Advisory Committee on Astronomy of the new Carnegie Institution, joining Edward Pickering, Simon Newcomb, Samuel Langley, and Lewis Boss. This seemed an opportunity to further his views as to how the Carnegie money should be spent, but Hale stood alone on this committee as a staunch proponent of astrophysics, and he had found difficulty in gaining support for some of this ideas. At first the institution made only small grants, but soon a committee was formed to study the establishment of a southern and a solar observatory. W.J. Hussey of the Lick Observatory was sent to investigate several sites in the Southwest United States, including Flagstaff, Mount Palomar and Mount Lowe, but Mount Wilson received the highest recommendation.

Hale decided to visit Mount Wilson himself and, with W.W. Campbell, Director of Lick Observatory, he journeyed up the mountain on June 25, 1903. Low clouds and fog covered Pasadena that morning as Hale, depressed by the gloomy skies and doubting if ``Wilson's Peak'' would provide for a satisfactory site for a solar observatory, started up the trail. All of his misgivings were replaced with delight, however, when halfway up the mountain he burst out into blue sky and brilliant sunshine. Hussey had preceded them, setting up a nine-inch refractor, and with this telescope Hale made his first solar observations from the mountaintop. Ecstatic over the excellent conditions, Hale decided he must build his observatory there. Already he saw, as Harold Babcock later described in his poem, ``In 1903''

A picture growing clear before his eyes
Of all that was to be in years to come
Upon that mountaintop

Soon after his return to Chicago, Hale applied to the Carnegie Institution for a great solar observatory. Not waiting for a response, he moved his family to Pasadena in December, partially because of his daughter's worsening asthma in the harsh Wisconsin climate. Hale returned to Pasadena on December 20, 1903, one year to the day the Mount Wilson Solar Observatory would become reality, and five years to the day before the first photographs would be taken with the completed 60-inch mirror.

A limited expedition from Yerkes Observatory to Mount Wilson was mounted, funded by Yerkes and several local California philanthropists. One of these was John Hooker, a founder of the California Academy of Science. For Hale, this was the beginning of a long relationship with Hooker, culminating in Hooker's donations of the funds for the mirror of the 100-inch telescope, named in his honor. A 15-inch coelostat with a 6-inch objective lens, originally used for eclipse observations, was brought to Mount Wilson for trials in March, 1904. Ferdinand Ellerman followed within weeks, and Adams and Ritchey migrated west two months later. When Francis Pease, who would become the chief designer of every major telescope on Mount Wilson, also left Yerkes for the West, Hale had brought almost all of the Yerkes staff to California, keeping intact the nucleus of a group that would soon make scientific history.

Mountaintop Conditions
Conditions on the mountain were still very primitive, a situation in which Ellerman reveled. Adams later described his first sight of Ellerman on his way up the mountain: ``He wore a `ten-gallon hat', high mountain boots, and a full cartridge belt from which hung a revolver on one side and a hunting knife on the other. I was greatly impressed and pictured a struggle for existence on the wild mountain top, which bore little resemblance to later actuality.'' The mountain could be reached only by a strenuous hike or by renting a burro. Adams wrote: ``Books could be written about the personal character of these sagacious beasts... One would deliberately expand his chest when the saddle was placed upon him so that the rider, after a good start, would presently find the saddle rolling beneath him at some awkward point in the trail...'' Hale had the misfortune of packing a valuable diffraction grating on the back of a burro who had a tendency to lie down and roll over on the trail. Still the animals made 60 trips transporting the parts of the Snow telescope up the hill without mishap.

Confident that the Carnegie Institution would fund the Solar Observatory, on June 13, 1904, Hale signed a 99-year lease with the Mount Wilson Toll Road Company for 40 acres on the mountaintop. The land owners provided the property rent-free, anticipating the world-wide fame the Observatory would bring to Mount Wilson and the increased tourist business that would mean. Hale was to make good use of the land that summer. With a $10,000 grant from the Carnegie Institution, the Snow solar telescope was brought from Yerkes, soon to become the world's first permanently mounted solar telescope. The massive stone piers were built before the year was out, including the 27-foot high south pier. The ``monestary'' (the astronomers' living quarters) was built, a powerhouse with gasoline-driven electric generator was constructed, and a water pump, reservoir and pipe lines were installed. With the new observatory already attracting a great deal of attention, many famous scientists were visiting even before observations were begun. By the time the Carnegie Board of Trustees met in December, Hale had already spent $27,000 of his own money financing his dream. Some thought him a reckless gambler, but others saw him as a genius and visionary who simply could not accept the possibility of failure.

It was at Martin's camp on the Mount Wilson trail, on December 20, 1904, that Hale received the news that the Carnegie Board had approved his plans for the Mount Wilson Solar Observatory (the word ``Solar'' was dropped with the completion of the 100-inch telescope in 1917). What the future held, only Hale could have imagined. Already, even before the Snow telescope was completed, he had discussed with Adams plans for the next solar telescope, one with a ``high tower and no tube'' and in his typical straightforward manner, climbed a tree with a telescope to test the seeing conditions such a telescope would enjoy. Already he was making plans for bringing the 60-inch disk from Yerkes to build the world's greatest telescope. Before that one was done he would be performing an even larger one. One great step forward would have been enough to assure a place in history for Hale and the Observatory he founded, but he planned one scientific revolution after another on Mount Wilson. Four years after the Observatory was begun, four great telescopes, including the world's largest solar and stellar instruments, would reside there. Many fundamental problems in astronomy -- the nature of sunspots, the temperature and composition of the stars, even the structure of the universe -- would gradually be addressed. Many of the world's greatest astronomers and physicists would make the pilgrimage to Mount Wilson to add to the contributions of the first small, select group working there, about whom Babcock wrote:

How fortunate that little group of men
Whom in those next swift years he chose to be
His friends and colleagues in the appointed task
Of realizing what he had foreseen!