SOUTHERN STARS

Evening Star, Issue 22448, 19 September 1936, Page 2

SOUTHERN STARS

A TELESCOPE FOR PRETORIA [By H. G. Wood, Union Astronomer, in ‘ The Times.’] . There has been an extraordinary development of astronomical observation in South Africa in the present century. The conditions are especially favourable, particularly in the interior of the country, a huge plateau at an average height of 4,500 ft above sea level. No visitor to South Africa over ceases to marvel at the clarity of the air, which affords a visibility enjoyed by very few, other parts of the world. The Union Observatory at Johannesburg, ' the National , Observatory of South Africa, was established in 1912. Some years later the large American observatories founded southern stations in South Africa. The first of these was the Yale University Observatory, whose large telescope was formally installed by the present king on his visjt to Johannesburg in June, 1925; and in 1927 the southern station of Harvard Observatory was moved from Peru to Mazelspoort, near Bloemfontein, and the' University of Michigan established the Lamont-Hussey Observatory on Naval Hill, Bloemfontein. In relation to its population, South Africa has more largo telescopes than any other country in the world. The largest telescope in _ the country is the 60in reflecting telescope of the Harvard southern station; there are a number of large refractors, a,27in, ,at Naval Hill, Bloemfontein, a 265 in at the Union Observatory, Johannesburg, a 26in at the Yale Station, Johannesburg, a 24in at the Royal Observatory at Cape Town, and a 24in at the Harvard Station. The country looks forward to the inauguration, -within the, next few years, of a new astronomical institution —the Radcliffe Observatory of Pretoria. Although new to South Africa, tho name of the Radcliffe Observatory is old in the annals of astronomy. It was founded in 1772; After ICO years of existence at Oxford, it has been neces sary for tho Observatory to find a new home, and the decision has been made to emigrate to South Africa. It is not a new thing for ah observatory to move. Observatories which were originally erected in sylvan surroundings and in a pure atmosphere have found themselves in the course of time beneath a pall of dust and smoke. The observatories of Paris and Berlin already have had to move-some distance out of town into a clearer atmosphere. The Radcliffe Observatory, although not smoked out of Oxford, has been crowded out. UNCHARTED SKY The problem facing the Radcliffe trustees was a difficult one, but there were some very powerful indications of the solution. The Nautical Almanac lists 290 observatories in the Northern Hemisphere and 36 in the Southern, a ratio of eight to one. Our knowledge of the stellar universe is therefore somewhat unbalanced, and all statistical in-vestigators-of- celestial problems have been seriously handicapped in their work by the scarcity of data concerning the sky visible south of the Equator. Although this disparity has now been removed from several branches of astronomical york, , new ; problems of astrophysics, which, demand the use of very large telescopes with powerful light grasp, are still not receiving due attention in the, south. The Radcliffe Trustees caine tp the decision, which has been approved’ by all astronomers, to obtain a large reflecting telescope and erect it in the Southern Hemisphere. . . . ‘ - When the British Association held its meetings in South Africa in 1929, visiting astronomers examined the possibili,tiS of various sites in South Africa for the new home for' the Radcliffe Observatory. Sir Frank Dyson, then •Astronomer Royal, and Dr Knox-Sbaw, the Radcliffe-, Observer, found a very promising site on a range 'of koppies, south-east of • Pretoria. Dr \>. J 3. Steavenson brought out a Cin telescop© from England, established a small observatory on tho selected site, and made observations of the atmospheric conditions over a period of six mouths. His report was favourable, the final decision for the Pretoria site was made, and an order'given' to 'the firm of Sir Howard Grubb, Parsons and Co. for the construction of a 74in reflecting telescope. This is of the same size as the telescope recently installed at Richmond Hill, near Toronto, by the University of. Toronto, through the gift of Mrs David Dunlap' in memory of,her. husband. The two telescopes are only smaller than the lOOin reflector at Mount Wilson and the 200 in reflector tinder construction for Mount Paloitiar. They will be the largest in the. British Empire, and the new Pretoria tele-' scope will be the largest south of the Equator. • . ' ' - ' • STAR-GAZING PRIESTS ■ The installation; of the Radcliffe Observatory at'Pretoria will bo a. great event is ; the astronomical history 5 of South Africa. The first astronomical : observations were probably made in this country in 1685 when Father Taehard, one of a party of Jesuit Fathers on a mission to Siam, called at the Capo and determined the longitude -by thedbservations of -JUpitcr’s satellites. Some 66 years later the Abbe de la OaiUe visited the. Cape of Good Hopelor the Paris Academy- of Sciences, and between 1751 and 1753 he compiled the material for a’ catalogue of 10,035 southern stars The Transit of Venus in 1761 was observed at the Cape. Soon after the second British occupation of the Cape, a permanent observa-

tory was established by an Order in Council of George IV. dated Octobci 20, 1820. This observatory; tho Royal Observatory at Cape Town, is still under the control of the British Admiralty. ' Sir John Herschel came to South Africa in 1834 to catalogue the nebulae of the Southern Hemisphere on the same plan ns that on which his father bad catalogued those of the Northern, The site of his observatory at Feldhauscn is marked by an obelisk, which is now a national monument of South Africa. The Transit of Venus of December 6, 1882, brought several astronomical expeditions to the , country. The work of the many South African astronomical institutions does not overlap. The work of the Iloyal Observatory at the Capo is fundamental. An accurate I knowledge of the position of the stars is the foundation of all astronomical -research and the star catalogues compiled at the Capo supply this for the stars for the south. Tho 24in photographic telescope is used for tho determination of tho distances-of the stars, a great work which is shared with the Yale telescope at Johannesburg.’ The : large, visual telescope at the Union Observatory at Johannesburg and tbe Lamont-Hussey Observatory at Bloemfontein between them survey the southern skies for the discovery of double stars and their laterobservation. The Union Observatory, with the help of the lOin EranklinAdams telescope, undertakes the observation of the asteroids when they come south, and is almost the only observatory in tho Southern Hemisphere undertaking such observations. It also observes regularly the occupations of stars by the moon, which bear upon the moon's complicated motions and* also on the question of the regularity of the rotation of our earth. With the larg reflecting telescope at Mazelspoort. long series of photographs are taken of the faint' variable stars in the' Milky Way and in star clusters, providing material for our knowledge of the structure of the Galaxy. One branch of astronomy has up to now not received due attention in tho Southern Hemisphere. The investigations pursued by tho present observatories refer mainly to the positions, the motions,- and’ the distances of the stars. Astrophysics, which attempts _ to answer the question, “ What is a star? ” is hardly tackled at all. Here is the field of research awaiting the new Radcliffe telescope. All our information of the real nature of a star, its size, its temperature, and its constitution is brought to us by the rays -of light from tho star. Since these must be analysed, as much light as possible must be collected and the great light gathering power of the 74in reflector makes it most suitable Tho field is almost untouched in the Southern Hemisphere. Our intimate knowledge of stars is all but confined tt those within the reach of tho great telescopes of, the north. Wonderful opportunities await tbe installation of the new Radcliffe telescope’ at Pretoria, and it- is confidently expected that the work done with it; will speedily justify the policy of emigration to South Africa.