Sydney Observatory Papers No.31
SYDNEY OBSERVATORY : 1858 to 1958 Part 9
By HARLEY WOOD
RECENT HISTORY
After Nangle’s 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
Melbourne’s 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 Nangle’s 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 Robertson’s 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. O’Connell, 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. Bronwer’s direction at
Yale.
In 1946 Sydney 0bservatory, began to number its publications in a
series of Sydney Observation Papers. This systematises Sydney’s 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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