Origins of the USNO Flagstaff Station and the 61-Inch Telescope

Steven J. Dick

US Naval Observatory, Washington, DC

This talk was one of two keynote addresses given at the rededication of the 61-inch telescope to Dr. Kaj Strand on April 14, 1997, at a scientific session in his honor at the annual meeting of the AAS Division on Dynamical Astronomy, held at Lowell Observatory, Flagstaff.

I. Search for a New Site

The first rumblings about a Naval Observatory station in Flagstaff date back to 1947. In that year a politically motivated plan almost succeeded in moving the entire Naval Observatory from Washington. Senator Millard Tydings was in charge of the Senate Military Affairs Committee, and Mrs. Tydings was on a District of Columbia committee to come up with a new Washington Hospital center. The site chosen for the hospital in 1947 was the Naval Observatory. Soon word came from the Navy Department that the Naval Observatory would have to move, within a month.

Naval Observatory astronomers, led by C. B. Watts, explained in detail how the move could not be undertaken in such a short time due to the need for continuity in the observations; they needed a minimum of one year, preferably two. This was granted. F. P. Scott was put in charge of site testing, assisted by Alfred Mikesell. Under the rushed circumstances they were given whatever resources they needed for site testing. Mikesell and others went down the Appalachian range visiting local meteorologists, as far south as Asheville, North Carolina. And although Flagstaff was a name already suggested by some, after consulting astronomers including Struve, USNO astronomer Gerald Clemence decided that the new site should be within 2 hours of Washington.

Site testing was done at four locations, two in the Lynchburg, Va and two in the Charlottesville area, using Polaris telescopes loaned from Palomar Observatory. On every clear night over 18 months, the telescope observed Polaris, looking visually for image motion. In addition a 5-inch Alvan Clark refractor was placed at each site to analyze seeing according to the Pickering scale. Eventually one of the Charlottesville sites, known as Piney Mountain, was selected. The Observatory was virtually packed up and ready to move when Tydings was defeated by underhanded McCarthy tactics. Within a few weeks the Observatory was told not to worry about moving. But the name of Flagstaff was not forgotten.

II. John Hall, the Equatorial Division, and the Origins of the Flagstaff Station

The man who was instrumental in the establishment of the Flagstaff station was John Hall . A graduate of Amherst and Yale, Hall was greatly influenced by Frank Schlesinger who got him started using an infrared photoelectric cell for his dissertation. His work in photoelectric photometry continued at Amherst beginning in 1938, and during the War Hall worked on radar at the MIT Radiation Laboratory, before returning to Amherst.

In late 1947 Hall received a letter from C. B. Watts, Director of the 6-inch Transit Circle Division at the USNO, asking if he would be interested in taking over from Burton as Director of the Equatorial Division. Hall applied after receiving assurances from Clemence, Watts and the Superintendent that the position as Head of the Equatorial Branch was less burdensome administratively than the other Divisions, and the opportunity for original research therefore greater. He also pointed out that there was a good nucleus of instrumental equipment, and Hall would have virtually a free hand in modernizing it.

Although Hall expressed reservations about leaving the college community, after extracting a promise that the USNO would purchase his unique polarization equipment from Amherst, he accepted. He arrived in a Division with U. S. Lyons, who had inherited an outmoded tradition of work on double stars; Lucy Day, who did the routine solar photography; and Bevan Sharpless, who was a creative intellect but whose health greatly impaired his work. Burton died only a month before Hall arrived. Hall wanted to do something new; and it was a turning point for the Observatory that Watts and Clemence brought Hall to the observatory just for this purpose. In retrospect it was clearly the beginning of a revival for the Naval Observatory, because Hall would eventually hire other creative people also.

The origins of the Flagstaff station was closely connected to the 40-inch Ritchey-Chretien telescope, a design as yet unproven, though the telescope had been completed in Washington in 1933. Hall was anxious to use the 40-inch telescope for his polarization work, but he also recalled a piece of advice from Schlesinger, who had said that it was a shame this telescope with its new design was located in Washington, where the power of its design could not be proven because of the bad seeing. Almost immediately upon his arrival in the Fall of 1948 Hall proposed to move the telescope.

But ironically, in the meantime he proved that the 40-inch was also very useful at its location in the middle of Washington. It turns out that Hall was extremely anxious to get his hands on a reflector at just this time, because he was in the middle of his work on interstellar polarization, and thus he set to work immediately on that problem of interstellar polarization upon his arrival in Washington. Within a few months he had not only proven that the 40-inch could be used in Washington, but also made one of the better known discoveries at the Naval Observatory. Meanwhile Hiltner had sent a paper announcing his discovery to Science; Hall sent one also and they were published together. Interstellar polarization awakened people to the idea of galactic magnetic fields, and a first step in discovering polarization and magnetic fields in other galaxies as well.

Within four months of his arrival, Hall had accomplished more with the 40-inch that its previous 15-year history, a testimony to the new telescope design, the new detector Hall attached, and a creative mind. Clemence and Watts must have been pleased.

The early success of Hall's work with the 40" only increased his desire to see it moved to a dark sky site. In 1949 Hall was given orders to go to Lick, Mt. Wilson, Inyokern, Lowell, Tucson and McDonald Observatories. In November, 1950, Hall and Mikesell drove to Flagstaff, consulted the Lowell staff and Lowell records, undertook site testing with some of the same instruments, and selected the site, a hilltop some five miles west of Flagstaff.

But selecting the site was one thing; getting Congressional support for funding was another. Between 1949-55 Clemence, and on at least two occasions Hall, testified at the Congressional subcommittee hearings attempting to get an appropriation for the move. Success came only in 1954, after Hall came to know Roy Elson, the administrative to Arizona Senator Carl Hayden, a grand old man of the Senate. In 1954 the money was appropriated, and construction began in Spring 1955.

Finally, the move could begin. The 40-inch and associated equipment was loaded on two flatbed trucks and moved to Flagstaff late in September, 1955.

Optical alignment of the telescope was begun 6 days after the trucks arrived, assisted by USNO instrument shop personnel. Art Hoag became first Director of the Flagstaff station. He was ably assisted by Joe Egan on the instrument side.

So, the Flagstaff station was well-established. Early work with the 40-inch included more polarization work, image tube work, scintillation work, photometry and photography. Pat Roemer came and began her comet work. Stewart Sharpless did spectroscopy with a spectrograph of his own design. Finally the 40-inch lived up to its reputation, and proved once and for all the worth of the Ritchey-Chretien design.

III. The 61-inch telescope

Meanwhile, events were again stirring back in Washington initiating the second part of our story: the 61-inch reflector. Once again, it was John Hall who set things in motion, because it was Hall's departure that brought Kai Strand to the Naval Observatory. Hall in fact hand-picked Strand as his successor as director of the Equatorial Division, now renamed the Astrometry and Astrophysics Division.

Strand and the 61-Inch Reflector

Strand had obtained his doctorate from the University of Copenhagen in 1938, worked under Peter Van de Kamp as a Research Associate at Swarthmore, and after War work was associated with Yerkes Observatory. In 1946 he became chairman of the astronomy Department at Northwestern University. The idea of the 61-inch goes back at least to 1953 and Strand's years at Northwestern. In that year Clemence and Brouwer asked Strand to chair an international conference on astrometry, one of the first conferences sponsored by the National Science Foundation. The purpose of the meeting was to get the most active astrometrists together "to see if we could somehow get astrometry revived. It had been in the doldrums." One of the problems discussed was the lack of a telescope that could observe parallaxes of faint stars such as white dwarfs and red dwarfs, at the low end of the HR diagram. This 1953 conference not only led to the AGK3R project and the Brouwer astrograph in Argentina, but also discussed the need for an astrometric telescope. By 1956 this was one of two projects (along with a new computer center featuring an IBM 650) that Strand was pushing at Northwestern.

The idea of a large telescope for determining parallaxes, driven by the discovery of low luminosity stars too faint to be seen with existing long-focus refractors, became Strand's personal goal. This need was expressed at several meetings, beginning with the Cosmic Distance Scale Conference in 1956, held at the University of Virginia and sponsored by the National Science Foundation. One of the two resolutions of the conference was to emphasize

"that one of the most urgent needs of astronomy is the determination of the distances of stars fainter than the thirteenth magnitude. Such stars are too faint to be observed with long-focus refractors; also existing reflectors were not designed to meet the astrometric requirements. The conference therefore recommends that an engineering study be made with the aim of producing a design for a reflector that will be suitable for the above-mentioned purpose. A Cassegrain-type reflector is indicated, with the secondary mirror more rigidly mounted than is customary. The aperture should be at least sixty inches so that stars of the eighteenth magnitude can be observed with exposure times not exceeding about twenty minutes. The instrument should be located at a site with a climate that is reasonably uniform throughout the year with regard to percentage of clear sky and quality of seeing. Such an instrument will be usefully employed for many decades."

There are 2 things to note in this statement. First we should not pass over lightly the use of a reflector for parallaxes. By far most parallaxes were undertaken by refractors, although at Mt. Wilson van Maanen worked with the 60-inch and 100 inch reflectors on parallaxes. Strand undertook a comparison of those parallaxes with refractors, and found that reflectors could be used for parallax, especially if designed specifically for that purpose. Secondly, we see already in this statement that the design of the telescope will be a Cassegrain; it will be a Cassegrain with a flat secondary and a coma-free field of a half degree, compared to van Maanen's coma free field one-tenth that size.

Returning to Northwestern, Strand formally proposed to the dean and vice-president that a telescope about 60 inches in diameter be built in Western Illinois, about 120 miles from Northwestern. But they did not consider it a high priority for the University. By April of the same year, 1957, Clemence and John Hall approached Strand about the possibility of taking over Hall's position as Head of the Equatorial Division, since Hall was moving on to Lowell Observatory. Although Strand had reservations about leaving a university position for a government job, he saw the possibilities for funding for his telescope especially with the explicit support of Clemence, and in August, 1958 cast his fortunes with the Naval Observatory.

Building on the resolution at the Cosmic Distance Scale Conference, Strand wasted no time in gaining more support for a large telescope. A similar resolution was passed at the Moscow General Assembly of the IAU in August 1958, where Strand served as President of the Commission on stellar distances and motions. In his trip report upon returning from that meeting, Strand wrote the Superintendent that

"I believe this engineering study can best be carried out by the U. S. Naval Observatory with the view of acquiring such a telescope from R and D Funds originating from ONR or DOD. When the question of R and D funds arises for FY 1961 or a possible reprogramming for FY 1960, this engineering study should be brought up for discussion."
Strand set out to make the telescope a reality.

In January, 1959 the Astronomical Council of the Naval Observatory approved the construction of the 60-inch facility. The Superintendent at the time was Captain C. G. Christie, whom Strand described as "knowing his way around the Pentagon, not afraid of raising his voice in presence of superiors, who would give in to his demands just to get him out of their offices." By memorandum of May 1959, Christie requested the Deputy CNO for Development to include two million dollars for the FY 1961 military construction bill. It was one of his last acts before he retired in June.

Navy approval was just the first step - the construction of the telescope itself required the approval of the Congress. Lest you think that the Congress was in the mode of easily giving money away to anything in astronomy in the wake of Sputnik, the 1.9 million dollar request was zeroed out by the House. The Navy filed a reclama with further justifications. Henry Giclas wrote Senator Carl Hayden (Az). And the project was tied to the giant Sugar Grove radio telescope project.

"Before passage there had been a couple of times where the project was in doubt. The Navy ran into a problem with the funding of a large radio telescope for communication, bouncing messages via the Moon. This required Vice Admiral -- Hayward, Deputy Chief of Naval Operations (Development) to refuse using the projected funding of the Observatory telescope project for the instrument. The radio telescope project was later discontinued because of overruns, and technical problems. The other problem arose when there seemed to be little support for the project in the Senate, until Henry Giclas of the Lowell Observatory got the staff of Senator Hayden's office to endorse the project. Giclas's letter was printed in the Congressional record."

In October, the Navy awarded a preliminary architectural and engineering contract to the firm of C. W. Jones in Los Angeles, the same firm involved in the design of the 84-inch telescope at KPNO, as well as telescopes at Mt. Wilson and Palomar. This was followed in March, 1960 by the complete contract. On July 2, 1960 the milcon bill was passed with 1.9 million for the 60-inch.

In August 1960 Corning Glass works was awarded a contract to provide the fused silica blanks for the primary and secondary mirrors at a cost of $182,000. Davidson Optronics was awarded a $72.,000 contract for figuring the optics. In April, 1961 the glass blanks were shipped to Davidson for rough grinding. May 25, 1961 groundbreaking. The building was completed in Sept 62. In Sept 63 the assembly of the telescope began. The following March the parallax program began.

The dedication of the 61-inch was held June 22-24, 1964, with a conference in honor of Hertzsprung, who was himself present. The introduction was given by Martin Schwarzschild, an astrophysicist who spoke of the 61-inch as "a beautiful example of that energy and daring that it takes for scientists to go into new techniques, fraught with possible technical difficulties, but full of promise of magnificent new results." Dr. Strand described the 61-inch itself; Henry Giclas and Luyten discussed proper motions, and Charles Worley the parallax and proper motion program that the 61-inch would undertake. Most of the rest of the conference was taken up with topics in astrophysics; only Fricke and van de Kamp spoke of astrometry, the latter on perturbations in stellar proper motions the year after his announcement of a planet around Barnard's star.

Even the work of the long-focus refractors was in the hundredths of an arcsecond regime, and it was the 61-inch that began to approach the milliarcsecond region. With that increase in accuracy, we are now doing a million times better than the ancient Greeks, and a hundred to a thousand times better than the 18th and 19th centuries.

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