Syd. Observatory 2
Skipper and First Mate Millard (Big Bear and Pepe)
Fri 19 Feb 2016 23:47
Sydney Observatory – Part Two
Transit of Venus Orrery. In 1760 Benjamin Cole of London built an orrery to demonstrate the transit of Venus. While not to scale, the orrery shows the relationship between Earth, Venus and the Sun for the period of the transit. Turning the handle causes Venus to pass across the face of the Sun, while Earth rotates about its axis. This replica was made by orrery maker Brian Greig in 2012.
Portrait of Edmond Halley (1656-1742) published a famous paper in 1716, urging astronomers to ‘diligently’ observe the 1761 transit of Venus. He wrote: “having ascertained with more exactness the magnitude of the planetary orbits, it may redound to their immortal fame and glory”. (Painting by Thomas Murray about 1687)
Edmund Halley’s Catalogus Stellarum Australium. (Catalogue of the Southern Hemisphere Stars) includes observations of the 1677 transit of Mercury, which he made from the island of St Helena. The English astronomer published an influential paper in 1716 urging astronomers to observe the transit of Venus from locations around the world, arguing that these measurements could be used to calculate the distance of the Sun and gauge the size of the solar system.
Longitude – Earnshaw’s Appeal to the Public. This is a reprint of a book published in 1808 by the English clockmaker Thomas Earnshaw. Earnshaw was one of the people most closely involved in the development of the chronometer. Feeling that he had not been adequately rewarded for his work by the British government, Earnshaw wrote this book. In it he sets out his claim for the superiority of his chronometers over those of other makers and appeals for better treatment.
A Voyage to Terra Australis. Matthew Flinders wrote up the details of his voyage in two volumes, (one – above right). In the book he discusses his circumnavigation of the continent in HMS Investigator, his shipwreck off the coast of Queensland and his nearly seven year imprisonment on the French island of Mauritius.
Sadly Flinders was dying by the time the book was published in 1814 and may not have seen a printed copy. He died on the 19th of July 1814.
Earnshaw 520 Chronometer. This is one of five chronometers (the box is modern) used by Matthew Flinders who called it “This excellent timekeeper”. Made by Thomas Earnshaw, it was the only chronometer still working at the end of the epic three-year voyage. No wonder Flinders was full of praise for it.
Chronometer Clock. A chronometer has to cope with a ship’s movement and the many climate changes on a long voyage. Ordinary types of clocks such as those with pendulums would either stop or run wildly fast or slow.
The accuracy of chronometers is due to the design of their internal mechanism. Thomas Earnshaw developed the final form of this mechanism in the 1780’s. This modern clock shows the internal workings of an Earnshaw chronometer.
Mariners Astrolabe. This is a reproduction of a mariners astrolabe found on the wreck of the Dutch ship Batavia. The ship hit a reef in 1629 with the eventual loss of 200 lives. Before Matthew Flinders time, mariners astrolabes were standard equipment.
Flinders Bearing Book. This book is a copy of the book in which Matthew Flinders recorded his observations of the Australian coastline. During his voyage Flinders was carrying out a detailed survey. At each location he first established the position of his ship with the help of a sextant and chronometers. He then measured the directions or bearings of any features that he could see. Later he used the information in his bearing book to draw up a map of Terra Australis or Australia.
Sextant. A sextant measures the angles by which a star or the sun is above the horizon. The angle at any place depends on both the local time and the latitude – how many degrees north or south the place is from the equator. By making observations with a sextant, navigators like Flinders could obtain both the time and the latitude. This sextant dates from 1787 and would be similar to the one used by Flinders.
Navigators no longer need chronometers, sextants and careful observations. They can use satellite navigation with the help of Global Positioning System (GPS) satellites. By picking up signals from three or more satellites, GPS receivers can work out and display positions to great accuracy.
The Star Observer Henry Chamberlain Russell at his desk. We were standing between the Observatory’s two domes, which was the office H.C. Russell spent much of his time here reading and writing about astronomy and meteorology. H.C. Russell pictured in January 1898. H.C. Russell was the government astronomer at Sydney Observatory, travelled to the International Astrophotographic Congress in Paris in 1887 on behalf of the Australian government. Many photographs exist of Henry and his family during that trip, in the one above you can see the family having fun in shadow of their ship’s mast and funnel on the sands of Egypt.
Transit Room pictured in the 1870’s. This photograph shows some of the equipment associated with the transit circle. In the centre is the clock that provided the daily signals to drop the time ball in the tower above and, through telegraph wires, the time ball in Newcastle. On each side of the clock are chronographs for recording time. The pivot tester is next to the clock.
The Transit Circle Telescope, Henry Alfred Lenehan observing. As in any 19th-century observatory, the telescope was at the heart of the work of Sydney Observatory. Known as the transit circle, it was used by astronomers to find the exact time, the positions of the stars and the geographical coordinates of the Observatory. To find time, the transit circle telescope relied on the regular daily spin of the earth. As the Earth spun, stars passed through the field of view of the eyepiece. Imagine a giant clock with only one hand: the stars are then the numbers on the clock face and the telescope is the hand showing the time.
The grand astronomical clock dial on the ‘Strasburg’ clock model, made in 1889 (on display in the Powerhouse Museum).
H.C. Russell, The Australiasian, 28th of February 1903 said “I think this transit instrument is, perhaps, the most important in the Observatory. Transit circles are telescopes that can only move north-south. Astronomers used them to determine the instant the stars cross or ‘transit’ the meridian – an imaginary line passing overhead from north to south”.
The observing couch offered a reasonable degree of comfort as the astronomers spent hours staring through the eyepiece. The couch was on rollers so that the observer could manoeuvre themselves into appropriate positions. Either end of the couch could be raised to provide support
Geoff Wyatt’s image of the 2004 transit of Venus was taken in the north dome here at the Sydney Observatory through a special filter that only transmits the red light of hydrogen atoms. He used a Coronado telescope and Nikon Coolpix camera to capture the spectacular image, which was the first winner of the David Malin Award, Australia’s premier prize for celestial photography.
We went into a small area set aside for Aboriginal creation and dream stories, we watched several child-like explanations for star constellations – here are two.
Whowie – The Bunyip: Many years ago there lived on earth Whowie the bunyip. No person or animal was safe when Whowie was about because he had the most insatiable appetite. The members of the tribe gathered to kill Whowie by lighting a series of fires close to the monster’s cave. When he was driven out by the smoke from the fires, the whole tribe attacked him with their spears. He was so big and strong they took all day to finally kill him. There has never been another bunyip to this day. But his shape still fills the sky during December. And Whowie is the largest of the Sky figures. Wathuarung – Victoria.
Marigu Jarn – The Hunter: Jarn is a youth who believed he was the best hunter of his tribe. He would hunt and show off his catch to everyone. He also thought he was the best man in the tribe that he deserved the best wife. Thus, he began to play his dancing sticks. As this did not work, he then chased Marigu, the seven sisters, through the bush to try catching a wife. In the evening sky in January, Jarn can be seen as the figure playing his dancing sticks, while the seven women appear as a group of stars huddled together to escape from him. Woorabinda-Biregada tribe – Queensland.
Wolf Creek Crater. The Djaru say ‘There was once a wild man in the form of a star. He saw a woman sitting in a spring of milky water, under which was tasty sugar leaf. In his hunger, he came down from the sky and tried to kill the woman to get the sugar leaf. She quickly moved and he plunged into the Earth, making the crater the Djaru call Kandimalal’. Another story is ‘when the crescent moon and the evening star passed very close to each other, the star became so hot that it fell to the ground causing an enormous explosion’.
Small chunks of rock floating in space are called meteoroids. As they fall through the Earth’s atmosphere, they heat up and generate visible streaks of light (meteors). If they strike the Earth, they are known as meteorites. Meteorites are generally classified as either stony or iron. The most common type are stony meteorites. The Henbury and Wolfe Creek meteorites, are mostly of nickel and iron.
Wolfe Creek Meteorites. Weight 945, 245 and 210 grams. Wolfe Creek, in the far north of Western Australia, is one of the best-preserved impact craters in the world. The 900 metre wide by 60 metre deep crater was formed 300,000 years ago when a 50,000-ton meteorite struck the Earth with great force. Identified by Europeans in 1947.
Henbury Meteorite. Weight 575 grams. About 4,200 years ago a meteoroid broke apart in the atmosphere before striking the Earth, 145 kilometres south of Alice Springs. The impact carved out 13 craters, the largest of which measures 180 metres wide by 15 metres deep. Europeans identified the site in 1899 but did not realise it was formed by a meteorite impact until 1931. Aboriginal people would not venture near the craters, known as Tatyeye Kepmwere in the Arrente language, fearing the fire-devil who came from the sun would fill them with iron.
‘Shou lao’ figure, China – date unknown. This figure of Shou lao or ‘the god of longevity’ was discovered in Doctor’s Gully, Port Darwin in 1879. Carved in pinite, the figure holds a peach and rides a deer. He is also named Shou xing which is the Chinese name for the southern star Canopus. From the northern hemisphere Shou xing/Canopus appears low in the sky and is rarely seen. The ancient Chinese therefore believed that seeing Shou xing brings long life and good luck.
Outside we looked back to the rear of the Observatory.
From here we had quite a view and of the War Memorial – this side dedicated to the Units of Volunteers from New South Wales who responded to the Empire call – South African War 1899-1902........and of course something for Bear’s trigger finger..........
ALL IN ALL FASCINATING, LOTS OF NEW STUFF
VERY WELL PRESENTED