THE McMath-Hulbert Observatory of the University of Michigan commenced operations on July 1, 1930. Before that date lay the history of the idea and its evolution from even smaller equipment than that available at the time.
It is probable that Mr. Willard Pope ('88e) of Detroit, vice-president of the Canadian Bridge Company of Walkerville, Ontario, interested the president of the company and his business associate, Mr. Francis C. McMath (C.E. Washington University '87, Hon.Alum. Michigan '31, D.Eng. hon. Wayne '37), in astronomy during the early 1920's. McMath's interest led to the acquisition of a series of small telescopes, the first of which was a three-inch altazimuth obtained in 1922. Since the mounting of these telescopes proved unsuitable, in 1926, after some urging on the part of his son, Robert R. McMath ('13e, A.M. hon. '33, D.Sc. hon. Wayne '38), president of Motors Metal Manufacturing Company of Detroit, F. C. McMath purchased a four-inch Bausch and Lomb refractor equatorially mounted and driven by a spring clock. Experience showed that this instrument could not be used satisfactorily out in the open, and, consequently, in 1927 R. R. McMath designed and built a suitable dome to house it. The spring clock was found reasonably satisfactory for short periods, but its rate was not sufficiently constant to keep the setting circle in proper position for the longer observations. It occurred to F. C. McMath that a telechron motor could be used for the clock drive instead of springs, and R. R. McMath undertook to design and build a sidereal clock with such a motor. This was installed early in 1928; it performed perfectly, and all clock troubles were at an end.
That summer R. R. McMath conceived the idea that the moon should prove an interesting subject for celestial motion pictures. He took such a picture, holding his own sixteen-millimeter motion-picture camera by hand against the eyepiece at an approximation of the telescope focus. After development, a fairly clear image of the moon appeared, and the picture showed that the idea had promise.
These motion pictures came into the hands of the late Director Ralph H. Curtiss of the University of Michigan Observatory through Henry J. Colliau of the Observatory staff. As a result of the vision and energy of Professor Curtiss, Messrs. F. C. and R. R. McMath agreed to undertake the design of an instrument especially adapted for the production of celestial motion pictures. It is Page 484a matter of great regret that Curtiss did not live to see the plan come to fruition.
In 1929 Judge Henry S. Hulbert (LL.M. hon. '14, LL.D. Wayne '36), long interested in astronomy, joined the enterprise. At that time he was the senior Judge of Probate of Wayne County, Michigan, and has since (1935) become vice-president of the National Bank of Detroit in charge of the trust department.
The Regents of the University of Michigan, in June, 1929, appointed Messrs. R. R. McMath, F. C. McMath, and Judge Hulbert honorary curators of astronomical observation, at the request of Dr. R. H. Curtiss. This was done in order to make possible close relations between the new observatory at Lake Angelus and the University of Michigan Observatory. Later, the titles of these curators were changed (see p. 487).
The observatory, which commenced operations on July 1, 1930, comprised a 10 ½-inch equatorial, mounted on a very heavy Bruce-type mounting with all of the auxiliaries thought necessary at that time. This observatory was described by the three founders in the University of Michigan Observatory Publications (Vol. 4, No. 4, 1931). Shortly thereafter, Heber Doust Curtis accepted the directorship of the University of Michigan observatories (see Part III: Department of Astronomy and Astronomical Observatories at Ann Arbor), and this proved to be one of the most fortunate events in the history of the enterprise. His unbounded enthusiasm and faith in the undertaking have been a continued inspiration to the founders. Dr. Curtis suggested that the name of the new observatory at Lake Angelus be the McMath-Hulbert Observatory, and in 1931 the three founders deeded it to the University of Michigan, for it had become apparent that the work should be carried on under University auspices.
The years 1931-33 were spent in perfecting the necessary mechanical equipment with which to take successful celestial motion pictures of the planets and of the shadow changes on the moon. The purely educational value of the pictures had previously been regarded as of paramount importance, but their scientific value was becoming more and more evident as time went on. Accordingly, in 1931 it was decided to try similar photographic work with the sun as a subject. Keivin Burns of the Allegheny Observatory was consulted as to the optics involved, and F. C. McMath furnished the funds with which to acquire the optical parts of the new instrument, which was christened by Dr. Curtis the "spectroheliokinematograph."
This instrument was attached to the eye end of the 10 1/2-inch reflector in June, 1932, after having been constructed by Messrs. Colliau and Smock in the University Observatory Shop from detailed drawings made by Curtis. Robert M. Petrie of the University staff spent the summer at Lake Angelus assisting in an effort to make the spectroheliokinematograph function. Spectroheliograms of solar prominences were secured that summer, but the first striking complete record was made of the ejection of a large eruptive-type prominence from a rather small sunspot on June 19, 1934, by Messrs. R. R. McMath and Petrie.
In the meantime, R. R. McMath had been building and discarding telescope drives and controls in an effort to secure one which would be nearly perfect. A very successful drive which utilized the method of frequency changing had been evolved by the summer of 1933. It became evident, however, that if extensive solar work were to be carried on, still further improvements were needed. The Detroit Edison Company joined with the observatory late in the summer of 1933 in an endeavor to evolve a satisfactory Page 485drive for the telescope which should be independent of the power system's line-voltage fluctuation and frequency variations. On December 1, 1933, the final drive was installed at Lake Angelus. Its fundamental element was a synchronous motor the speed of which could be varied by means of frequency variations in the current, effected with a thermionic tube control. Worm gearing only connected the motor to the telescope. This drive proved itself to be everything that could be desired and has been adopted for other telescopes at other observatories.
Between 1930 and 1934 Director Curtis had shown the pictures taken at the McMath-Hulbert Observatory before many audiences, both scientific and popular, and through the University of Chicago Press the pictures secured a wide distribution all over the earth. The work was closely watched by the scientific world, and professional astronomers were generous in their praise.* This early success was recognized by the Franklin Institute of Pennsylvania, which awarded the three founders the John Price Wetherill medal in May, 1933, "for their design and construction of novel apparatus for the making of motion pictures of astronomical subjects."
The reception of the solar motion pictures led R. R. McMath to suggest a solar tower telescope. With the help of President Ruthven, $20,000 was secured from the Rackham Fund as an initial grant. R. R. McMath and his brother, Neil Cook McMath (C.E. Cornell '14), then made an extended tour of inspection to other observatories, and in particular to Mount Wilson Observatory. All possible aid was given by the scientists at these observatories. It developed, however, that it would be most desirable to build an instrument which would take world rank as to size and light grasp. Soon after the McMaths' return from their trip, the founders of the McMath-Hulbert Observatory and H. D. Curtis held a conference and decided to proceed with plans for such an instrument. It soon became obvious that the cost of the instrument would greatly overrun the initial grant. A very substantial grant was then obtained from the McGregor Fund of Detroit, and in addition a number of individuals made generous contributions.
The resources available for design and construction proved to be particularly fortunate. R. R. McMath was president of the company in whose shops the 10 ½-inch instrument, with its complicated accessories and other equipment, had been built. Neil C. McMath was vice-president of the Whitehead and Kales Company of Detroit, one of the larger steel fabricators of this section of the country. Edison Pettit, of the Mount Wilson Observatory, put his accumulated experience in solar physics and solar observation unreservedly at the disposal of the McMath-Hulbert Observatory. Every effort was made to avoid mistakes which had been made in the past.
Ground for the new tower telescope was broken on July 16, 1935, and the instrument was completed, except for temporary optical parts, on June 30, 1936. A description was published in the University of Michigan Observatory Publications (Vol. 7, No. 1, 1937). Fortunately, the founders had purchased enough optical pyrex from the Corning Glass Company late in 1934. This alone permitted the work to be undertaken as soon as it was. Nevertheless, certain parts of the optical equipment were not Page 486ready at the end of June, 1936. Director W. S. Adams, of the Mount Wilson Observatory, thereupon loaned the McMath-Hulbert Observatory sufficient optical equipment with which to begin its program. Even as late as May, 1937, the observatory had not yet received its own six-inch diffraction grating and was still using one loaned by the Mount Wilson Observatory.
Edison Pettit accepted an appointment as a research associate of the McMath-Hulbert Observatory in June, 1936. He spent July and August supervising the observational program at Lake Angelus. Although it had been hoped that the results would be unusual, no one had even imagined such results as were actually secured. Certain phenomena which the astronomer had only strongly supposed to exist he could now, for the first time in astronomical history, see as often as desired and examine minutely. The results of measurements of the first summer's negatives are described by R. R. McMath and Edison Pettit in the Astrophysical Journal (Vol. 85, No. 4, 1937).
The light-pressure theory which has been advanced, particularly in England, in explanation of the solar prominences, appears to have been disproved by the observations of 1936. The films indicate that a source of chromospheric material exists high above the solar surface, and suggest strongly that there is a solar atmosphere, notwithstanding that all eclipse evidence seems to deny its existence.
In the winter of 1936-37 some alterations to the instrumentation and some important additions were made. The changes and additions were the result of one year's use of the instrument and were, in the main, evolutionary in character.
Dr. Edison Pettit continued as research associate and spent June, July, and August, 1937, at the observatory assisting with the observational program. The results of the summer's observing, together with more observations by McMath and H. E. Sawyer in the autumn, were described in Mount Wilson Contributions, No. 597. The tower performed with perfect satisfaction during its second summer, so that only minor changes in the instrumentation were made during the winter of 1937-38, the principal one being the design and construction of an auxiliary photoelectric guiding apparatus.
Dr. Pettit was again at Lake Angelus observing with the tower telescope during the summer of 1938. Measures of the records of the previous summers had made it evident that motions perpendicular to the line of sight, deducible from the customary spectroheliograms obtained with the tower telescope and the spectroheliokinematograph, could tell only a part of the story of motions on the sun. Accordingly, Sawyer and George Malesky spent the summer evolving a technique for measuring the motions of prominence material along the line of sight, using the 10 1/2-inch equatorial and its spectroheliokinematograph.
It was found that the velocities at all points of an area under observation could be determined by giving a suitable motion to the slits of an orthodox spectroheliograph. The necessary motions were obtainable only in an instrument of special construction, and Mr. Julius F. Stone of Columbus, Ohio, made a grant of $10,000 to the observatory for the design and construction of the new radial velocity spectroheliograph.
The Stone radial velocity spectroheliograph was built in the winter of 1938-39, and its installation in the tower telescope just to the north and above the main spectroheliograph was completed by November, 1939. A complete optical system, using the existing driving and Page 487controlling mechanisms, was added to the fifty-foot tower for directing and focusing sunlight on the Stone spectroheliograph.
At the close of the summer of 1938 Dr. Pettit felt that he had accomplished his work at the observatory, and he accordingly did not participate in the observing in the summer of 1939. During the 1939 observing season the first strictly simultaneous records of the motions of solar prominences in light from two different elements, calcium and hydrogen, were obtained; and also in this observing season the first pictures of the actual beginnings of two prominences were made.
For some time past, Judge Hulbert, Director R. R. McMath, and his father, Francis C. McMath, had discussed plans for the general enlargement of the observatory. Inasmuch as the tower telescope had become a proved success, the field for the spectroheliokinematograph, mounted as it was on the 10 1/2-inch equatorial, was very limited. Upon the death of F. C. McMath on February 13, 1938, it was decided that the 10 1/2-inch should be replaced with a memorial twenty-four-inch equatorial telescope. The work on the design and manufacture of the Francis C. McMath twenty-four-inch reflecting telescope was started early in 1939, and the instrument was practically completed by June 30, 1940. It has been described in the Publications of the University of Michigan Observatory (Vol. 8, No. 6).
Throughout the regime of Heber D. Curtis the curators, who at his request were newly designated honorary curators of the astronomical observatories of the University of Michigan, have served as an advisory board. Neil C. McMath took his father's place as a curator in March, 1938. Before the end of the year R. R. McMath accepted the directorship of the McMath-Hulbert Observatory, and Willard Pope soon afterward replaced him as an honorary curator.
The simultaneous recording of prominence motions in three dimensions and in the light of different elements showed the great desirability of adding still another simultaneous record, that of the energy changes in prominences and other solar features. Preliminary designs by Director McMath for a new instrument indicated that at least a seventy-foot tower telescope would be needed, and tentative plans for a new telescope and an office building to house the staff, provide a library, darkrooms, laboratory facilities, and, probably most important of all, a suitably equipped instrument shop, were drawn up. In September, 1939, the McGregor Fund made a grant to the University of Michigan of $100,000 and Mr. and Mrs. R. R. McMath deeded the necessary land to carry out these plans. The new building was dedicated on May 25, 1940, together with the tower telescope structure (without instrumentation). Work was immediately started on the new McGregor instrument, and the new tower telescope was in service by the end of 1941.
The completion of the McGregor Tower perfects the Lake Angelus equipment to the point where concurrent observations of space motion and of the energy in solar activity can be made with ease and precision. Experience gained in making the simultaneous records in hydrogen and calcium light and the simultaneous radial velocity records indicates that such concurrent observation has many times the value of an isolated record.
Although the new concurrent observations will supersede, in many ways, the original "one-variable" observations, several important results have emerged from the early motion pictures of solar prominences. For the first time, astronomers have been able to see the Page 488motions of prominences projected on the disk of the sun, and these pictures, as well as the pictures of prominences projected on the sky, show conclusively that 95 per cent of the material in prominences is moving downward to the sun.
The beginnings of simultaneous observations have enabled us to demonstrate pictorially, and by measurement, that the gases which compose a solar prominence are perfectly mixed and in some instances to derive the geometrical relations of the prominences to definite points on the surface of the sun. Based on these first results of the method of concurrent observations, new instruments have been evolved, a staff of astronomers has been organized to do cooperative research, and a novel program for continued investigation and observation of the sun has been developed.
The phenomenal growth of the observatory to an "institution responsible for one of the greatest developments of the decade — the continuous record of the motions of the solar atmosphere" has required the close and enthusiastic cooperation of many individuals.
H. E. Sawyer and O. C. Mohler, assistant astronomers, together with J. T. Brodie, assistant, comprise the present scientific staff. Messrs. Sawyer and Brodie have been at Lake Angelus since late in 1933. Dr. Mohler, after a close association with the observatory which began in 1933, joined the staff permanently in 1940. C. W. Guenther, instrument maker, and two machinists, under the supervision of engineer George Malesky, are engaged in completing the instruments for the McGregor Tower at Lake Angelus.
The three founders of the observatory — R. R. McMath, Judge H. S. Hulbert, and F. C. McMath — have been completely responsible for the organization of the observatory. Judge Hulbert has been an invaluable aid to the observatory whenever his many duties would permit his participation in its activities; and until his death Mr. F. C. McMath contributed from his long engineering experience freely and generously in the design of buildings and new instruments. His advice and counsel in all matters pertaining to the observatory have been greatly missed during the last three years. From the earliest beginnings of the observatory, Dr. R. R. McMath has been directly responsible for the design and construction of all of the instruments and buildings and has, in addition, initiated and supervised the research of the observatory.