Publications of the Astronomical Society Of

PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC Vol.63 June 1951 No. 372 AN ASTRONOMICAL VISIT TO SOUTH AFRICA John. B. Irwin Goethe Link Observatory, Indiana University During the summer of 1950 the writer had the privilege of making photoelectric observations at three of the South African observatories with the capable assistance of Arthur N. Cox, a graduate student at Indiana University. During the four-month stay in the Union, visits were made to four other observatories. Thanks to the speed of modern air transportation, it is possible for a university professor to spend his "summer vacation" in the fabulously clear African winter observing the still comparatively neglected skies of the southern hemisphere. I am indebted to the Office of Naval Research for the grant that made this research possible and to the Graduate School of Indiana University which supplied me with such an efficient assistant. Johannesburg is some 9,700 miles and 47 hours by air from New York as Pan American flies it via Lisbon, Dakar, and Leo- poldville. The Constellation Clipper "Yankee Ranger" lifted us off the LaGuardia runway at noon on May 29 and after six inter- mediate stops deposited us at the Palmietfontein Airport of Jo- hannesburg at 7:23 p.m. Springbok (South African) Time on May 31. Disembarking from the plane we turned around and looked upward, drinking in for the first time the superb southern Milky Way, the Southern Cross, Alpha and Beta Centauri, the Carina star cloud, and the Magellanic Clouds. The next morning, after breakfast, where a choice of cereal p- was made between Jungle Oats and Mealie Meal, we visited the ^ Yale-Columbia Southern Station on the attractive campus of the rl. University of Witwatersrand. Here amid the eucalyptus trees we s') met Professor Cyril Jackson and his charming wife and inspected the 26-inch photographic refractor, which ranks with the long- Ill © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 112 JOHN Β. IRWIN focal-length refractors at the McCormick, Allegheny, and Cape Observatories in the number of stellar parallax determinations. This telescope was installed at the instigation of Professor Schles- inger in 1925 under the vigorous direction of Dr. Harold S. Alden. The aluminum-alloy tube, thirty-six feet long, is mounted inex- pensively in a high, narrow building with two sliding roof panels in such a way that observations must be made on, or very close to, the meridian. A five-inch Ross lens of eighty-inch focal length, mounted on the tube of this large refractor, is used as a catalogue camera, supplying the plates for the Yale photographic reobserva- tion of the A.G. zones from +9° to —30°. Dr. Paul Skoberla, who before the war was astronomer at the now abandoned Breslau station at Windhoek in South West Africa, assists Professor Jackson in the operation of this station. At present, much of the time of these two astronomers is taken up in preparing for ship- ment tens of thousands of astronomical plates which are being sent to New Haven. Johannesburg is a city of almost a million population and, in some respects, it could be likened to a pocket edition of New York. Its phenomenal growth and industrialization since its founding in 1886—and especially in the past decade—has so befouled the high veld skies that exposure times, even with modern fast plates, are as much as twice as long as they were ten or fifteen years ago. With diminishing returns from the parallax program becoming apparent, the Observatory has branched out into other fields, no- tably that of photoelectric photometry. This type of astrophysical research requires not only the clearest possible skies but also a more flexible type of telescope mounting. It is indeed fortunate that the 26-inch refractor can be provided with a new "home" which meets these more stringent requirements. Later in Sep- tember, on the morning of my final departure from Johannesburg, the local newspaper carried a story telling of the future move of the Yale-Columbia station to Mount Stromlo, Australia, on the invitation of Dr. R. v. d. R. Woolley, director of the Common- wealth Observatory. A new dome and mounting for the 26-inch will be provided, as well as housing for the astronomical staff. Canberra, a city of some fifteen thousand population, has a recent law forbiding its industrialization or residential expansion. © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System AN ASTRONOMICAL VISIT TO SOUTH AFRICA 113 Dr. A. D. Thackeray, the new director of the Radcliffe Observ- atory, kindly drove down the thirty-six miles from Pretoria to take us back with him. Before leaving, however, we visited the Union Observatory, located some three miles east of the Yale- Columbia station halfway up Hospital Ridge. This Observatory was first founded as a meteorological station after the Boer War under the directorship of R. T. Α., Innés, becoming the Union Observatory in 1912 ; a 26^-inch refractor was obtained after the first World War. Here we met the director. Dr. W. H. Van Den Bos, noted for his observations of double stars. The Observatory, with the aid of two quartz-crystal clocks, supplies a time service to most of South Africa. At the time of our visit a new faint aster- oid, which had been picked up near the south celestial pole by E. L. Johnson, was being eagerly followed because a preliminary orbit indicated an extraordinarily short period. The 10-inch f/4.5 Franklin-Adams star camera with 15-inch square plates is an ideal instrument for discovering new asteroids and comets. It has no device, however, such as the one attached to the finder of our 10-inch Goethe Link camera, whereby the motion of faint objects can be accurately set off, enabling the plate to record very faint asteroids and comets. The Leiden Observatory Southern Station is on the grounds of the Union Observatory; its equipment consists of the twin 16-inch Rockefeller refractor, each objective of 90 inches focal length. The telescope has now been converted to photoelectric photometry, a 1P21 photometer having been attached to one "barrel." We met and talked "shop" with Dr. A. J. Wesselink, the Leiden observer, who is noted for his superb photographic photometry of eclipsing variables. We also met the assistant director of the Leiden Observatory, Dr. P. Th. Oosterhoff, who was spending a number of months in the Union measuring photoelectric colors of the southern Β stars, with additional observing time on the 74-inch Radcliffe reflector. Wesselink has since be- come the chief assistant at Radcliffe, his place at Johannesburg being taken by Dr. Th. Walraven. The Union Observatory, because it is some one hundred fifty feet higher than the Yale-Columbia Southern Station and somewhat farther away from the railroad yards and downtown Johan- © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 114 JOHN Β. IRWIN nesburg, has somewhat the better photoelectric observing con- ditions, although not what one might reasonably expect at an altitude of 5800 feet. Present hopes are that the Union Observa- tory can be relocated away from Johannesburg's smoke, and a site some thirty miles northwest of the city and twenty miles west of Pretoria, near Hartebeestpoort Dam, is being seriously con- sidered. There are also hopes of acquiring a new 74-inch reflector. The Leiden Southern Station will probably be moved to the new site also. Leaving Johannesburg we found the hour's drive to Pretoria along the well-paved national highway one of great interest. The countryside with its rolling brown fields and towering eucalyptus trees reminds one very strongly of parts of California, although the many natives afoot or on bicycles, the Afrikaans-English road signs, the left-hand driving on the highway, the distinctive types of architecture, all reminded us that this was indeed a foreign country. Soon after the distant view of the Voortrekker Monu- ment atop a small hill just south of Pretoria warned us that our long trip was nearly over, the aluminum-painted Radcliffe 74-inch turret became visible on Waterkloof Ridge to the right of the main highway. A few miles more over a red dirt road winding upward through eucalyptus, wattle, and protea brought us to the Observatory entrance and paved roads again. Four nights later, with the expert assistance of Director Thackeray and bushy- haired Dr. David Evans, we were hard at work on our photoelectric program. The Radcliffe Observatory was first established in Oxford, England, in 1771 and was transferred to its present site in 1937. The 57-acre site, a gift of the municipality of Pretoria, is just over 5000 feet above sea level and is some four air-line miles from the center of this rapidly growing city of a quarter of a million. The view to the north is over the near-by eastern Pretoria suburbs of Muckleneuk, New Muckleneuk, and Waterkloof, while seven miles to the west the furnaces of the large Iscor steel works occasionally light up that whole section of the sky at night. The view to the south is, however, over open veld with the lights of Johannesburg just visible on the far horizon. The region south of the zenith (δ = —25° 477) is, of course, the critical one; in © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System AN ASTRONOMICAL VISIT TO SOUTH AFRICA 115 fact, when I asked one of the astronomers how the telescope be- haved north of the zenith he replied that he couldn't remember ever having used it there.

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