Woodford Observatory And The Transit Of Venus
astronomical station

In the 9th December 1874 a rare astronomical event occurred when the planet Venus passed directly between the Earth and the Sun. To observers, Venus then appeared as a small black dot slowly passing across the face of the Sun.

To the astronomers of the 18th and 19th Centuries, a transit of Venus was an opportunity to follow the advice given by Edmund Halley (of comet fame) in 1716.

That by observing the next transit of Venus (1761) from two widely separated points on the Earth's surface, it would be possible to calculate the distance of the Sun from Earth.

The astronomers took Halley's advice, and some of them journeyed to the Southern Hemisphere to observe the 1761 Transit of Venus, while others prepared to make their observations from the Northern Hemisphere. The results were very disappointing for two main reasons. Firstly, the difficulty in finding the exact longitude of the Southern Hemisphere observing stations.

Secondly, the difficulty in observing the instant of contact between Venus and the Sun due to atmospheric unsteadiness produced by the Sun's heat as well as distortion in the shape of Venus caused by irradiation. Also, the fact that Venus has a dense atmosphere made it even more difficult to note the precise moment on contact with the Sun. Disappointing results may be, but valuable experience was gained for the next Transit of Venus which was only eight years away.

The 1769 Transit of Venus, was of course the most famous of all transits of that planet, due to its historical connection with Cook's First Voyage. However, the scientific value of the observations did not quite match its fame. Although the results were a vast improvement on those of 1761, they still fell short of what was required to give a good approximation of the Sun's distance from Earth. Once again valuable lessons were learned, but the next Transit of Venus was not due until 1874.

When Henry Chamberlain Russell was appointed to the position of New South Wales Government Astronomer in 1870, his ambition was to bring the Sydney Observatory into the international world of astronomy. He soon found the ideal project in which to be involved - The 1874 Transit of Venus.
Northern observatories were already planning to send observing parties to the Southern Hemisphere.

Russell began planning for the event with great enthusiasm. With the aid of the Royal Society of New South Wales, the Government was persuaded to advance £1000 towards the project. With the finances now under control, Russell was able to get down to the real business of preparing for the long awaited Transit of Venus.

One of the first items on Russell's agenda was the choice of three suitable sites for observing stations in addition to Sydney Observatory, spread over as wide an area as possible. But there was nothing haphazard about the final choice of these extra sites. First of all, the geographical position of them had to be taken into account. However, there were other important considerations, as Russell points out: "In addition to this, there were two conditions to be borne in mind in making the selection - viz., weather, and telegraphic convenience for determining longitude."

"I had for two years previously caused special meteorological observations to be taken at various places during the month of December.These indicated Woodford as about the most promising station for clear and steady atmosphere, and made it evident that the observers should not all be stationed at Eden, but divided between the coast and the mountains. Bathurst and Goulburn were alike in chance of clear weather; but Goulburn was th better station geographically, and was therefore selected. Eden weather reports were not encouraging; but as the advantage of the position was so much in its favour, it was decided to make it the fourth station ".

It is important to note here, that when Russell spoke of Woodford as the proposed site of the observatory, he did not mean the present township of Woodford, which at that time did not exist. He was referring to 'Woodford', the Blue Mountains home of Sydney business man and well known amateur astronomer, Alfred Fairfax, which is now better known as the Woodford Academy

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Apart from its clear and steady atmosphere, Russell had other very good reasons for his choice of Woodford as one of his out stations. Of great importance was its proximity to the railway and the electric telegraph lines which followed the railway. Also, Fairfax, as well as making his property available for a temporary observatory, had offered Russell the use of his 4% inch refracting telescope. This telescope, was at that time considered to be one of the best of its type in Australia.

Russell's next task was to equip the three observatories and to find suitably trained observers to man them. In this he was fortunate, because at that time, Sydney Observatory and the Lands Department were jointly carrying out a trigonometrical survey of N.S.W. To carry out the survey, the Lands Department had employed a number of surveyors who were also competent astronomical observers and would require very little extra training for the Transit of Venus observations. The Lands Department was also able to supply Russell with a number of astronomical instruments for the project. The extent to which Russell depended upon the Lands Department for both observers and equipment for the three out stations, is clearly shown in the following lists of observers and instruments sent to Woodford:

  • Observers: P.F. Adams, New South Wales Surveyor General.
  • L. Abington Vessey, Surveyor, Trigonometrical Survey
  • George D. Hirst, Well known Sydney amateur astronomer
  • Eccleston Du Faur, Survey Department
  • Also, a photographer, Mr. Bischoff, as well as two carpenters
  • The astronomical instruments used at Woodford were:

  • A photoheliograph by Dallmayer, (a telescope specially designed to photograph the Sun)
  • A siderial clock by Cooke and Sons;
  • a chronograph .
  • The 4 inch Schroder telescope lent by A. Fairfax .
  • A 3 inch telescope by Cooke supplied by the Survey Department .
  • A portable transit instrument, also supplied by the Survey Department .
  • A chronometer
  • As Russell had been able to obtain only one photoheliograph, he now had to decide from which observatory it would produce the best results. He soon chose Woodford because of its clear and steady atmosphere.

    Preparations for the Transit of Venus began at Woodford on Monday November 23rd, when Adams, as leader of the Woodford party, began marking out the site for the observatory, which was, according to Adams:......" about 200 yards westerly from Mr. Fairfax's house (Woodford), and the same distance northerly from the Western Railway and Telegraph Line, and nearly upon the summit of the main dividing ground between the waters of the river Cox on the South and the River Grose on the North..."

    The rest of the party had arrived at Woodford by the 1st of December, and by the 5th, the observatory buildings, which were timber framed with canvas cladding, had been erected and the instruments installed. On the 6th the observatory was connected to the electric telegraph system, and was now able to receive time signals from Sydney Observatory.

    It was now possible to complete the necessary astronomical observations to fix the exact latitude and longitude of the Woodford Observatory. Clear skies enabled these observations to be successfully completed on two successive nights. Preparations for the big day were now as complete as they could be.

    The 9th of December began with an almost clear sky, which was about the best thing one could say for it. There was also a hot dry westerly wind, which, by 10 o'clock had reached gale force. By 10:30 a.m. the temperature in the clock room had reached 92° Fahrenheit (about 34° C.). By this time, the observers were already at their stations:

    Vessey at the Fairfax 4 inch telescope; Hirst at the photoheliograph; and Du Faur at the 3 inch telescope. Fairfax, although not an official observer, was a very experienced observer, and was on hand to assist whenever needed.

    It was also about this time when Adams became concerned not only about the adverse effects of the rising temperature on the observers, but also on the accuracy of the clock.

    "My greatest anxiety," he reported, "was for the maintenance of an even temperature for the clock as possible, and but for the continued revolution of the fan ventilator and the constant application of wet blankets (on the outside of the canvas-clad observatory buildings), we should have found it difficult even to exist in the closed room " Because blindness can be swift and sure unless special precautions are taken when observing the Sun, it was, at that time the practice to attach special dark glasses to the telescope. Two such glasses had been attached to the 3 inch telescope at Woodford. Both of them were soon broken by the intense heat of the Sun, and unfortunately for Du Faur there were no replacements.

    To continue observing, Du Faur smoked one of the telescope lenses. The result was almost instant and disastrous. The lens had developed a maze of cracks.

    However, Du Faur continued his work with a very faulty telescope, and together with some observations with the 4% inch telescope when it became available, he managed to produce some worthwhile results. As well as the adverse weather conditions, there were some other minor distractions. Such as, unsteadiness in the instruments caused by strong wind gusts, and interuptions from passing clouds. However, the final results from Woodford were described by Russell as excellent.

    When the final results from Sydney Observatory, Woodford, Goulburn and Eden were received in London they were found to be of considerable value in determining the Sun's parallax. From Henry Russell's point of view, the Transit of Venus project was an outstanding success. He had achieved his ambition to bring the Sydney Observatory into the international world of astronomy.

    But what of the overall results of the 1874 Transit of Venus?

    A great improvement on the 1769 results, but still not good enough to provide us with the true distance of the Sun from earth. Also, the hopes that the new photography would produce the desired results were soon dashed. Even the best of the hundreds of photographs taken were not sharply defined enough to allow for the extreme accuracy required in measuring them.

    After the 1882 Transit of Venus observations, which still did not come up to expectations, it was decided that this method 'was not capable of such precision as had been hoped.'

    transit of venus

    Since the 1874 and 1882 Transits of Venus, new methods of finding the distance of the Sun from Earth have been found which are very accurate. So, does this mean that the next Transit of Venus will hold no interest for the astronomers or the public?

     Hardly likely. By the 7th June 2004, astronomers have thought of many good reasons why such a rare astronomical event should not pass unnoticed.
    transit of venus 2004