Sydney Observatory Papers No.31

Part 9



After Nangles death Harley Weston Wood was Acting Government Astronomer until October, 1943, when he was appointed Government Astronomer. At that time the War was affecting the work of the Observatory and where was a great increase in the demand for astronomical information. The fighting services needed to know the amount of light at any time in wide areas of the world and to have ready, in a form suitable for large numbers of newly trained men, information for scouting, navigating and surveying. In 1942, a booklet, Elementary Astronomy for Service Use was prepared at the Observatory and published using funds of the Donovan Astronomical Trust. This quickly went through several editions. In 1943, mainly to provide bearings for artillery purposes, nomograms and tables were prepared for the computation of azimuths of a number of bright southern stars and of the North Pole Star. On a number of occasions, too, the staff was asked to examine and report on inventions designed for use in navigation or surveying. The time service was continued and fairly complete arrangements were made for tile maintenance of this and other essential services from a site in the grounds of the Court House at Katoomba should it become impossible to carry on in Sydney. The optical parts of several of the telescopes were removed and stored in a place of safety until 1944.

The work on the Astrographic Catalogue was continued. Over six thousand stars from the meridian catalogues of La Plata Observatory were reduced to the equinox of the Catalogue (1900) and a study was made of the systematic differences between these catalogues and the Sydney Catalogue of 1068 Intermediate Stars The transit programme was revised to provide observations of star places in those areas of the sky for which the stars from the La Plata catalogue were deficient in [pg. 26] number. The observations were made differentially with respect to the Catalogue of 1068 Intermediate Stars, the system of which therefore applies to the whole of the Sydney zone of the Astrographic Catalogue. These reductions and observations were complete by 1945. It was found, too, that plates were still not available, or else were unsatisfactory, for a small number of centres and these were retaken in 1944 and 1945 after the lens of the astrographic telescope was replaced. The computation of plate constants was resumed and by 1947 the constants were made available for those volumes which had previously been published without them, as well as for the volume being currently published. At present thirty nine volumes, of the planned fifty two, have been published, three more are at the printers and all of the remaining ones are in manuscript ready to be produced as the funds become available for the printing.

In recent years Sydney Observatory took on another task for the great astrographic project. Melbourne Observatory, which had been working on the zone from −65° south to the south celestial pole, was closed as a State institution in 1944. After a meeting of the National Committee on Astronomy had discussed Melbournes share in the Astrographic Catalogue, Wood visited Melbourne in August, 1947, to examine the recording and report on the state of the work. Melbourne Observatory had planned to publish the work in eight volumes of which, at that stage, three had been published. Two more, Volumes 4 and 5, where in a stage in which it had been planned to send them to the printer although it had been accepted that revision would be necessary during the proof reading. A considerable amount of work had been done on Volume 6 and smaller amounts on Volumes 7 and 8. All of the plates had been taken and reference stars were available or the whole zone. At the 1948 meeting of the International Astronomical Union the Melbourne work was discussed and it was decided to ask Sydney Observatory to undertake its completion. The Union offered to provide resources for the printing of the Catalogue. Sydney undertook the work and after the records were moved from Melbourne to Sydney in 1949 the necessary revision of Volumes 4 had was begun. At the Rome meeting of the International Astronomical Union in 1952 funds were voted for publishing some of the volumes. The arrangement made was that Dr. Jules Baillaud, President of the Carte du Ciel Commission of the Union, would see the volumes put through the press in. Paris and Volumes 4 and 5 were sent to him in 1953. Volume 4 was published in 1955 and Volume 5 in 1957, and, the work progressing steadily, Volume 6 was sent to Dr. Baillaud in 1956 and Volume 7 in 1957. The preparation of the final volume is now going ahead.

For over sixty years the astrographic work has been an important part of the programme of Sydney Observatory, which has determined more star places than any other observatory. The zone allotted to Sydney was one of the richest in the sky and equal in area to the largest done by any observatory and now, in addition to this Sydney Observatory has done an appreciable part of the work originally allotted to Melbourne.

A transit programme, not associated with the astrographic work was undertaken in 1944, 1945 and 1946 to determine right ascensions of stars culminating near the zenith at Mount Stromlo and Adelaide for use with photographic zenith tubes which were planned for those centres. The instrument on Mount Stromlo has been recently established.

In recent years the traditional interest in double stars has been revived. In 1943 visual measures of double stars were begun with the 11½-inch refractor which had been left in commission during the war. During the work the performance off this telescope was much improved by placing the lens in a new mounting designed in the observatory, to reduce the effects of flexure of the glass under its own weight. [pg. 27] From 1946 to 1953 a series of measures was compiled by making measurements of double stars which appear on the photographic plates taken for the Astrographic Catalogue. Although these are not as accurate as results from photographic plates taken especially for the purpose, they are equal to good visual measures, and, what is valuable, yield observations of the stars as they were up to sixty years ago. Since 1953, Sydney Observatory has been taking photographs of double stars with the standard astrograph. In this case about twenty exposures of the double are taken on a photographic plate and, although it is not possible to measure very close pairs, which are more likely to have rapid motion, accuracy is a good deal better than can be achieved by visual means.

The observation of occultations of stars by the Moon in its movement across the sky was begun in 1938 and continued ever since. Almost four hundred occultations have now been observed. These observations are used in an internationally organised programme to keep a watch on the position of theMoon and at intervals they are gathered together and used in a discussion of the motion of the Moon. Since the timing of the occultations depends on the rotation of the Earth some of the apparent irregularities in the Moon's motion are the means of investigating variation of the rotational speed of the Earth.

The part that the Observatory can play as an educating agency in the community, referred to by Governor Sir William Denison when it was being founded, has always been important and has grown more so in recent years. There is always a steady demand from the public for information on astronomical matters, often trivial but sometimes quite important. Apart from the legitimate satisfying of natural curiosity about the Universe beyond the Earth, information is frequently given for legal, architectural or other purposes in which some specialist knowledge is needed. This stream of inquiry increases enormously when something of public interest such as a comet or an eclipse appears and it became a veritable flood when the first artificial satellites were launched in 1957.

The conducted inspections which take place on four evenings each week are another feature of the educational work of the Observatory. During these the uses of the instruments are examined and on fine evening visitors have the opportunity of viewing through the telescope the most attractive celestial objects in the sky at the time. In this way more than three thousand people each year are able to visit an observatory and there is always a waiting, list for the inspections. In 1949, W. H. Robertson prepared a course for the group study called Kits, organised by the Department of Tutorial Classes of the University of Sydney. Many groups in New South Wales are being introduced to astronomy through this Kit. An orrery, working model showing the relative motions of the Sun, Moon and Earth, was designed and built in the Observatory workshop in 1952 and has proved a source of interest particularly to parties of school pupils, and, perhaps even more, to their teachers, who have the difficult task of explaining these rather complicated motions. Lectures have been arranged for students of Teachers' Colleges and articles prepared for journals such as The Education Gazette and The Australian Mathematics Teacher, as well as for the popular press. With A. P. Mackerras, chairman of the Board of Visitors of the Observatory, Wood has in the last years, given lectures under the auspices of the Department of Tutorial Classes of the University of Sydney. Another valuable aspect of the educational work is the encouragement of amateur interest in astronomy. The New South Wales Branch of the British Astronomical Association has its regular meetings at the Observatory, the staff of which gives a good deal of attention to fostering its activities, but is repaid by the interest of a group of people which are well informed on astronomy and sympathetic [pg. 28] towards the work of the Observatory. This interest is occasionally valuable to us when we seek services for our work as seen in the readiness of E. W. Esdaile to make the cell for the 11½-inch lens.

The Observatory maintains a library which is a very valuable one in the branches of science immediately related to our work and which is frequently used by scientific workers who wish to refer to publications otherwise not available in Sydney. As well as the books and periodicals obtained by purchase we receive the publications, of many observatories of the world in exchange for our own. This arrangement is a usual one for astronomical publications and undoubtedly the Observatory is the object expressed by Denison when he urged the foundation of the Observatories as a means of connecting this Colony with the scientific societies of Europe and America.

Several valuable additions to the equipment of the Observatory have been made recent years. A co-ordinate measuring micrometer was ordered in 1948 from the London firm of Hilger and Watts and was delivered in 1953. This instrument, which is capable of measurement with an accuracy of better than one twenty five thousandth of an inch, is used for the measurement of celestial photographs. a new photographic lens of focal length about seventy two inches was delivered from, Taylor, Taylor and Hobson in 1955. The star images on photographs taken with this instrument are extremely good over a field of diameter eight degrees which is much more than was possible with our previous instruments. Between 1949 and 1952 a new dome was constructed to house the astrographic telescope, on which is also, mounted the camera with the new lens. This provides another example of the support Sydney Observatory has from amateurs since the contractor for the building, A. York, and several members of the staff of Morts Dock Engineering Company, which made the dome, are friends of the Observatory through the British Astronomical Association. The instrument mounted in this dome is the astrographic telescope bought from the Government of Victoria after Melbourne Observatory was closed. Other recently acquired equipment includes a thermostatically controlled room for our clocks and two calculating machines.

In 1953 the observation of the places of minor planets was begun. The planets form a numerous group of bodies which have orbits around the Sun, for the most part between the orbits of Mars and Jupiter. The largest of them is, Ceres which has a diameter of about 480 miles and the known ones range downward in size to only a few miles. About 1,600 minor planets have been given several numbers, as is the practice when orbits of reasonable reliability can be assigned to them, but many more have not yet been numbered. Even many of the largest known ones need observations to improve their orbits, sometimes even to avoid them becoming lost. There are, too, many interesting dynamical problems associated with the minor planets which call for comparison of observation with theory. For example the minor planet, Icarus (number 1566), discovered in 1949, which is the one which approaches nearest to the Sun, may prove useful in determining the mass of Mercury and in providing a test of the Theory of Relativity. At Sydney observations are being made of the minor planets which come south of the equator, many of them too far south to be easily observable from places in the northern hemisphere. There are many northern observatories engaged in this work but only three in the southern hemisphere. In 1954, an apparatus, since cried in other observatories, was designed and made in our workshop to assist in guiding during photography of minor planets. Usually there are too faint to be seen in the telescope through which the guiding must be done while the photograph is being taken and, if guiding is done on a star, the minor planet moves during the exposure and the light does not fall continuously on the one place on the photographic plate. The apparatus moves the wires on which the guiding is done so that the image of the [pg. 29] minor planet remains in the same place while the stars trail. Be this means much fainter minor planets may be photographed. One use which is made of the observations of minor planets is in defining the co-ordinate system to which star places are referred. The difficulty is that everything in the Universe is in motion and it is necessary to define some standard of rest relative to which the motions of the stars may be measured. One important standard of rest is the plane in which the Earth moves in the Solar System. This was formally found by observations of the Sun and of the large planets but the observations of the minor planets are now more favoured because they are more precise. The data is provided by intensive work on selected minor planets, whose orbits are well known. As such a minor planet crosses the sky it passes through zones where the stars have been catalogued by different observatories or at different times and the observations offer a means of comparing the systems in which the star places have been compiled. Work with an objective of this kind, which requires much greater care than the ordinary measurements, was begun at Sydney in 1955, since when series of observations have been made on six of the selected minor planets.

Towards the end of Nangles time, W. C. Graham, who had a very long service with the Observatory, was replaced by E. E. Adderley who after four years was followed in 1942 by W. H. Robertson. K. P. Sims was added to the staff in 1951. It is largely due to Robertsons energy that the leeway in the preparation of plate constants for the astrographic volumes was so quickly made up that a successful start has been made with the minor planet programme. Sims is working on the photographic observation of double stars and on the occultation programme. The increase in the professional staff enabled us to foster for a great deal more observational work at night. In 1951, H. F. Pinnock was appointed to the staff of the New South Wales University of Technology, part of his duty being to maintain the instruments at the Observatory. In 1954 he was appointed to work full time in the workshop of the Observatory and this capacity to service our instruments and make new ones is proving of much value.

In 1947 the Astronomer Royal, Sir Harold Spencer Jones, visited Australia and on February 24 attended a meeting of the Board of Visitors of the Observatory. The weight of his approval for the programme of the Observatory was an important influence in the obtaining of new equipment and in the beginning of new lines of work. Of value in this direction also are the contacts Wood made during his visits to Observatories in Europe in 1955. This visit was initiated nominally for Wood to attend the meeting of the International Astronomical Union in Dublin in September. Here, among other things, he was able to have extended discussions, in the Commissions of the Union if which, is a member, with colleagues abroad who are working in astrometry and particularly with those who have been associated with the development of the work of the Astrographic Catalogue. After the meeting Wood was able to visit centres where positional work is being done. These centres included some in England, in particular Greenwich, Leiden in Holland, and Brussels in Belgium, where he had the advantage of discussion with the chairman of the Minor Planet Commission of the International Astronomical Union, Dr. S. Arend. In France, where the astrographic work is being vigourously developed he benefited from conference, in Paris, with Doctors J. Baillaud and P. Coudere, and, in Toulouse with Professor E. Paloque. In Italy he renewed acquaintance with Father D. J. OConnell, formerly Director of our valued neighbour Observatory at Riverview and now Director of the Vatican Observatory.

Early in 1955 arrangements were made with the Director of Yale University Observatory, Dr. D. Brouwer, for Sydney Observatory — to co-operate with him in photographs of zones of the southern sky, for the production of catalogues of stars. Yale Observatory has been prominent in this work for many years.[pg. 30] Dr. Brouwer came to Australia in September in connection with this programme and remained until February, 1956. The wide experience that Dr. Brouwer has of fundamental astronomy, and of astronomical work in particular, made this association, especially valuable to us. By August, 1956, photography of zones centred on −35°, −90°, −85°, −80°, and −75° was complete. These plates are to be measured under Dr. Bronwers direction at Yale.

In 1946 Sydney 0bservatory, began to number its publications in a series of Sydney Observation Papers. This systematises Sydneys contributions to the the libraries of sister institutions and gathers together separate pieces of work into Papers includes whole which is gradually becoming appreciable. The word not only reprints of formal contributions to scientific journals, but anytime, it is wished to place on record, such as those history which will be number thirty one in the series. Observational results of the Observatory, other than those published in the Astrographic Catalogues, appears in the Papers. In 1950 and 1951 five of the Papers were devoted to a study of planetary motion in which the motion of the celestial body is considered unaffected by the other planets. Tables were given for the solution of the notion in the less easy cases.

The broad aims of Sydney Observatory remain the same so they were stated by Denison before its foundation to provide service, including education, to the community and to engage in a programme of work as a contribution to astronomical science. An observatory situated, as ours is, in a large city must always welcome the demands which the community must make. 0n the other hand, participation in an active programme of observation is necessary to the vitality of any Observatory. The bulk of the population and wealth of the world must always remain in the northern hemisphere and this adds to the opportunities and responsibilities of the necessarily fewer observatories able to observe the Southern Skies. Although our Observatory is at the centre of a city which produces much atmospheric pollution and light in the sky and prevents astronomers very fast optical systems or making photometric observations, there still remains a field of work in which they are but little handicapped, the accurate measurement of positions and motions of celestial bodies. This field included the work on minor planets and double stars which should remain valuable. There exists in our Observatory a large number of celestial photographs of old epoch, some over sixty years old. These plates, originally, taken for the Astrographic Catalogue, now nearing completion, represent a great store of valuable material, envied by younger observatories, and need to be exploited. New photographs for this purpose are being taken and, by comparing the places of the stars as measured on the old and new plates, it be possible to find the motions of the stars in the years intervening between the two. This work, combined with that of other observatories working in other parts of the sky, will make an important contribution to the data available for use in the study of the great star system in which the solar system is situated.


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