History - San Luis Observatory

Buildings housing the Dudley Observatory expedition in San Luis, Argentina. The Olcott Meridian Circle was in the larger of the two buildings. The telescope sticking out of the smaller building was the refractor used for photometry.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Staff of the Dudley Observatory in San Luis, Argentina. (Identified by Trudy Bell)

Beginning at left: Merton I. Roy, James M. Fair, Heroy Jenkins (at rear), Arthur J. Roy (with beard in front), Paul T. Delavan, Richard H. Tucker (center rear), Meade L. Zimmer, Louis Z. Mearns, William B. Varnum, and Roscoe F. Sanford.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This photo came from the family of Meade Zimmer, shedding new light on the identities of the staff members.

The Dudley Observatory
San Luis Southern Observatory

A Centennial Remembrance

As we commemorate the 100 year anniversary of the establishment of Dudley’s South American observatory and the beginning of its program of stellar observations and measurements, it would seem an appropriate time to reproduce the forward to that massive cataloging effort, in order to better gauge a sense of the spirit of care and determination that Lewis Boss and his corps of Albany astronomers brought to the task of undertaking both the critical observing regime and the meticulous compilation effort for this massive astrometric project, at that far away frontier outpost.
                                                                              Ron Barnell
                                                                               April, 2009

 

San Luis Catalog of 15333 Stars for Epoch 1910

Introduction

“The expeditionary character of the San Luis Observatory calls for a more detailed statement regarding plant, equipment and operations than would be required in the case of a permanent observatory. A full description of essential features is therefore offered, that those who handle the catalogue may judge of its merits and deficiencies.”

Scope of the Catalogue

“The San Luis Catalogue, made possible through a cooperative arrangement between the Carnegie Institution of Washington and the Dudley Observatory at Albany, N.Y. embodying the concluded positions of stars observed at San Luis, Argentina, constitutes one of the steps in a general program formulated by Lewis Boss, with the object of producing the positions and motions of all stars brighter than magnitude 7.0, together with those fainter stars which , at the time of the conception of the undertaking, gave promise of yielding determinate motions. Since the derivation of the motion of a star involves the comparison of its positions over a considerable lapse of time, and since in many instances no present-day observations existed, it became necessary to re-observe these stars. Thus the San Luis Catalogue fills many gaps in observational material. It likewise helps to amend the disparity between observations taken in the northern and southern hemispheres.

In addition to the above mentioned motives for observations of southern stars, it was realized that a program including observations in both the northern and southern hemispheres might be arranged to reconcile some of the bothersome discrepancies encountered in the formation of a smooth system of fundamental star places extending from pole to pole. Past experience in forming fundamental systems has indicated the difficulty in fixing the equator, due to widely varying systemic errors, found even in the case of modern catalogues of high precision. Combinations of catalogues observed nearly simultaneously from northern and southern stations afforded the best means for linking the star places from pole to pole.

These results, however, include outstanding errors due to personality and to the peculiar functioning of the various telescopes employed. Therefore, in formulating the general program it was arranged to observe a selected list of stars with the same instrument, both from the northern and southern hemispheres; moreover the same observers were in large part engaged in both series of observations, those taken at Albany, N.Y. and those at San Luis, Argentina. How far the anticipations were realizes may be judged from the presentation of the results in the following catalogue pages”. . . . . .

Photos:
#3 - Title Page San Luis Catalog

#4 (Close-up) - tabular half page column listings (Southern star measurements)

"Tale of Two Southern Observatories"

The Legacy of the Dudley Directors
By Ron Barnell

This April, Dudley Observatory celebrates the centennial of the opening and first light of its southern hemisphere observing station at San Luis, Argentina. Undertaken by Director Lewis Boss (1876-1912), the story of the establishment of the facility, the many difficulties of running it at a distance, and the varied perils the staff astronomers faced at this remote site on the Argentine pampas, were best described in an engrossing publication by science writer, Trudy Bell. (*title-link).
As an extension of his stellar proper-motion studies in the northern hemisphere, Lewis Boss began a preliminary cataloging program of select measurements of star motions, using the Olcott Meridian Circle that was located at the Albany observatory. Encouraged in this endeavor by other astronomers, such as James Keeler at the Allegheny observatory, (who was undertaking his own related parallax stellar measurement catalog), Boss, with his proper-motion studies attained a leadership role, when Dudley Observatory was named as a pilot facility of the Department of Meridian Astronomy, under the aegis of the newly formed Carnegie Institute, in Washington, D.C. With this impetus and the  new funding now made available to Dudley, Boss, and his staff, were now able to plan for an extension of the survey program to the southern hemisphere, with the purpose of integrating measurements from the stars that can never be seen from the N. latitude of Albany.

Negotiations with the government of Argentina ensued, with the final site selection being located near a remote school, on the wind swept plains, close by the southern town of San Luis. For several years, from 1909 until the closing of the observatory in 1913, a staff of several astronomers and calculators, under the supervision of astronomer Richard H. Tucker, made thousands of sequential star measurements, at every dark-sky opportunity, and as the southern Argentine weather allowed For this bold and far reaching astronomical adventure, the Olcott Meridian Circle was sent by steam-ship to South America. Tedious months were spent in erecting the instrument on concrete pillars and in finely tuning the coordinate reading micrometers. At San Luis, the staff also carried out a stellar magnitude survey, utilizing an early photo-electric apparatus with a 4” refracting telescope, also brought from Dudley. With this setup, they were able to obtain values of stellar brightness for select southern stars, which were included as a supplement to the proper-motion readings. Lewis Boss had passed away before the closing of San Luis, but now the work was carried on by his son, Benjamin Boss, who formally assumed the directorship of the Dudley Observatory.

As the final measurements were made, and the staff prepared to close the observatory (San Luis was never meant to be a permanent facility), Boss and the staff prepared to receive the massive amounts of paper-work that would entail many years of reductionist manual calculations, (in that pre computer era), to derive the proper motion values for all of the individual stars observed and measured in South America The first result of this massive effort was the publication of the “San Luis Catalog of 1533 Stars for the Epoch 1910” (Epoch 1910 refers to a stars right-ascension position on the sky in that reference year). Several years of additional labor with the use of the calculating engines at Dudley to further reduce the complete dual hemispheric readings of stellar motions, resulted in a more comprehensive compilation effort with the publication of a proper motion star catalog in 1928, ultimately leading to a final comprehensive installment in 1937, simply titled as” The Dudley General Catalog of 33,342 Stars.”

These publications served well into the space-age, as a reference source for the study of stellar motions, and allowed astronomers to forge a frame work that (used in conjunction with the  associated distance or parallax studies) began to show the first true picture of the interaction of the stars in the spiral arms of the Milky Way Galaxy.

Related to the catalog measurements, was Boss’ efforts at formulating an  understanding of the motions of the individual members within many associated star clusters, with an eye to determine the effect on the star-system as a whole, and in particular as it moved across the sky over  the course of thousands of years. Using the Hyades cluster in the winter constellation of Taurus, as a reference, Boss was able to verify this “streaming” effect that appeared to carry the individual members of a cluster to a common radiant point, as was projected on the celestial sphere.

In addition, the stellar motion studies derived from the time-consuming calculations of the Dudley astronomers, became an integral part of much of the present day understanding of the complex motions of stars in both binary and multiple pairings and provided a prolific source of data that would be later used in determining the orbital parameters of large scale stellar associations.

As seen today, in its 100 year retrospective, the proper motions studies, begun by Lewis Boss, at Dudley’s southern field station at San Luis,  not only greatly extended the scope of astronomical knowledge of the late 19th century, but in addition .can be viewed as a pioneering endeavor, pointing to the future of astronomical research. Today there are several prominent South American observatories, established in the later 20th century, where major research projects are carried on, and are sponsored by many of the world’s major astronomical research centers. Like San Luis, these facilities were established at their present locations, so that the astronomers of today would have access to the particular span of the sky, visible only in the southern hemisphere.

Present day astronomers, involved in research at the modern observatories, such as Cerro Tololo and the European Southern Observatory in Chile, carry on in the tradition of the San Luis astronomers, as they strive each clear night to uncover the secrets of the Universe, hidden in those far southern skies. They may often pause, as surely did the Dudley astronomers, to view with silent wonder, the incomparable beauty of the Milky Way and the galactic center, as they arc high overhead, among the luminous stars of the southern firmament.

Benjamin-Apthorp Gould was the first American astronomer to receive a Ph. D in Astronomy, (Germany, 1848). Several years later he was appointed to be the first director of the newly found Dudley Observatory, (situated in what is now North Albany). Gould served as director from 1855-1859. Returning to his native Boston after his tenure as director, he became involved with Harvard, and the work being done on the Draper catalog, involved with stellar positional measuring, etc.

Several European observatories had put forth a proposal for a massive mapping project of the heavens. Known as the Carte du Ciel, it was to be a comprehensive stellar cartographic effort, (before the era of wide-field Schmidt camera mapping, (e.g., NGS /Palomar/1950’s.) Select observatories around the world were to be assigned the plotting of stars on a strip on the sky, covered at their location, by roughly 20* in celestial longitude (right-ascension).

Gould had long ago expressed an interest in mapping the southern skies, and became actively involved in the project. Seeking out sites in the southern hemisphere , he was led to a consideration(from the Brazilian Emperor, an amateur astronomer) of an area within the Federated Republic of Brazil, later settling on the frontier area region of the Plata Estuary in Argentina, with its vast pampas, featuring both clear horizon sight lines and the promise of cloudless skies.

In 1868 the government of Argentina formally invited Gould to come to Argentina, for the purpose of establishing a national observatory. The new facility was installed at Cordoba in 1871, and later incorporated into the Universidad Nacional de Cordoba. With the use of both the Repsold meridian and other telescopes that were installed at the new Facility, Gould and his assistants began to systematically carry out the mapping of the southern skies, with unprecedented accuracy and diligence. With the utilization of photographic plates and zonal charting methods, they were able by 1874 to secure 82,537 observations of over 70,000 star positions.

Along with primary magnitude determinations, Gould and the Cordoba astronomers also observed some 1,064 circumpolar transits, and 1,711 time stars, for the correction of clocks and chronometers. With these series of observations, the observatory was able to furnish by telegraph, the correct time, to be utilized by both the Argentine railway system and the shipping port of Buenos Aires.

The projected scale of this astrometry enterprise was described in a quote from a New York Times article, of August, 1875.

“The great work which is destined to immortalize Dr. Gould and the Cordoba University is the grand map of the Argentine heavens, about to be published by order of Congress under the title of Uranometria Argentina. It will compromise thirteen charts, with tables annexed, showing the magnitude and positions of 8,500 stars, taking in the whole of the southern heavens and ten degrees of the equator. The sheets will be given to press immediately, and their publication will doubtless be hailed with delight by all the scientific world. Dr. Gould further expects to have four volumes of observations ready for press by the end of 1875.”

Several expanded editions of the catalog followed, The Cordoba Zone of Astrographic Plates and Catalog, was one. A final edition followed in 1892, known as the Cordoba Durchmusterung. It was compiled mainly by Gould’s assistant, J. M. Thome (Gould died in 1896).This edition became the southern hemisphere extension to the Bonner-Durchmusterung, published in Europe The publication charted 613, 959 stars, down to about the 10th magnitude , all lying south of declination -22*. Gould was honored for the body of his work at the Cordoba Observatory, by being awarded the gold medal of the Royal Astronomical Society, in 1883.

 One famous outcome of Benjamin Gould’s astronomic survey work in South America was his realization of a prominent zone of bright stars that seemed to lie across a defined section of the sky. This feature, later designated as, Gould’s Belt, appears as a ring of stars, infused with molecular clouds, and prolific with new star formation. As its appearance was best delineated from the far southern hemisphere. Gould was able to trace this band of hot, massive stars from the constellations Orion, and Puppis, to the Scorpius-Centaurus association, and beyond. Lying along the 3,000 light year expanse, are such naked-eye supergiant members like, Rigel, Sirius, and Antares , and a multitude of other hot and youthful stars, belonging to the local spiral arm of the galaxy.

With his insights into the astrophysics of the large scale features of the Milky Way Galaxy and the resulting charting of the heavens, the work of Benjamin Gould joins with the massive astrometric survey labors of Lewis Boss, and both exists as historic markers in the enlightenment of 19th century Astronomy.

Both men, each one time Dudley Directors, in their own way realized part of a dream, to extended the vision of the astronomical community of the 19th century, and thereby encompass the far southern skies into the knowledge base of the times.  100 years of San Luis history is joined with that of Cordoba, as across several hundred miles of the Argentine Pampas, (as the Condor flies), two observing facilities evolved from  two men, that   saw the possibilities of a southern hemisphere location to become an outpost for the frontiers of astronomical research.

At this time, as we remember the 100th anniversary of San Luis, it is worthwhile to reflect on the rare and special connection that Dudley Observatory shares, one directly linking the legacy of the Directors, with the history of and the evolution of Astronomy in the southern hemisphere.

Note*
* In one of the ironies of the story, the San Luis Director, Richard Tucker, had previously worked as Cordoba under Benjamin Gould. Having been involved there for nine years on the Cordoba Southern Star Catalog, being fluent in Spanish, and having an intimate knowledge of Argentina were among the deciding factors that led Boss to appoint him the head of the Dudley Southern Station.