Leviathan of Parsonstown
Encyclopedia
Leviathan of Parsonstown is the unofficial name of the Rosse six foot telescope. This is a historic reflecting telescope
of 72 in (1.8 m) aperture
, which was the largest telescope in the world from 1845 until the construction of the 100 in (2.5 m) Hooker Telescope
in 1917. The Rosse six foot telescope was built by William Parsons, 3rd Earl of Rosse
on his estate, Birr Castle
, at Parsonstown (now Birr
in County Offaly
, Ireland
).
, and constructed steam-powered grinding machines for parabolic mirrors. His 3 ft (90 cm) mirror of 1839 was cast in smaller pieces, fitted together before grinding and polishing; its 1840 successor was cast in a single piece. In 1842, Parsons cast his first 6 ft (1.8 m) mirror, but it took another five casts, before he had two ground and polished mirrors. Speculum mirrors tarnished rapidly; with two mirrors, one could be used in the telescope while the other was being re-polished. The telescope tube and supporting structure were completed in 1845.
The mirror was 5 in (13 cm) thick and weighed almost 3 tons. This required a mirror cell to support and to prevent the mirror deforming under its own weight. The length of the tube and mirror box is about 54 ft (16.5 m); including the mirror it weighed about 12 tons. The tube is supported at the mirror end by a "universal joint", a hinge with two axes, which allows the tube to be inclined through a large range of altitude and also to be turned through a limited range of azimuth. The azimuth range is limited to about one hour by the supporting walls that flank the tube on its eastern and western sides. The walls are 23 ft (7 m) apart, 40 ft (12 m) high, and 71 ft (21.5 m) long. A chain and counterweight keeps the telescope in balance, another chain with a winch controls the altitude. A rack and pinion
beam underneath the tube controls the azimuth. This beam is connected to the eastern supporting wall, where it can move on a circular iron arc to allow the telescope to change altitude.
The tube is of the Newtonian
design with the eyepiece
on its western side. At low altitude, the observer accesses the eyepiece from a wooden gallery that spans the distance between the walls and can slide up and down guides to follow the telescope in altitude. A cage on the gallery moves sideways to reach the eyepiece at different azimuth. At high elevation, curved galleries on top of the western wall are used, which can be moved across the wall to follow the telescope in azimuth.
.
The purpose of the telescope was to re-visit the nebulae in the catalogues of Charles Messier
and John Herschel
. These catalogues list star clusters as well as nebulae, and the question was whether the latter were merely unresolved star clusters or genuinely nebulous regions of space. If resolved into stars they might be the first galaxies
to be identified as such. Parsons discovered that several nebulae had a spiral structure, suggesting "dynamical laws". The most notable spiral nebula observed by Parsons was Messier 51
, which he resolved into stars.
After William Parsons (the 3rd Earl of Rosse) died in 1867, the 4th Earl (Laurence Parsons
) continued to operate the six foot telescope. From 1874 to 1878, J. L. E. Dreyer worked with the telescope and began the compilation of his New General Catalogue of Nebulae and Clusters of Stars
.
Although the 4th Earl built a smaller 3 ft equatorial
in 1876, the six foot telescope remained in use until about 1890. After his death in 1908, the telescope was partly dismantled, and in 1914, one of the mirrors with its mirror box were transferred to the Science Museum
in London
. The walls remained. The tube, second mirror box, and universal joint survived.
, there was renewed interest in the six foot telescope in the 1970s. Gradually, the telescope became a visitor attraction. But it was not before the 1990s that plans to actually rebuild the telescope came to fruition. In 1994 the retired structural engineer
and amateur astronomer
Michael Tubridy
was called in to research and re-design the Rosse six foot telescope. The original plans were lost, and so it took detective work to review the remains of the telescope, incidental comments in observing logs, and contemporary photographs taken by Mary Rosse
, wife of the 3rd Earl. Reconstruction work lasted from early 1996 to early 1997. It had been planned to include a working mirror, but due to budget constraints this had to be left for a separate project.
The new mirror was installed in 1999. Unlike the speculum
original, and unlike modern aluminium- or silver-coated glass mirrors, this is made of aluminium, as a compromise between authenticity and utility in astronomical observation.
Reflecting telescope
A reflecting telescope is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from...
of 72 in (1.8 m) aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
, which was the largest telescope in the world from 1845 until the construction of the 100 in (2.5 m) Hooker Telescope
Mount Wilson Observatory
The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles...
in 1917. The Rosse six foot telescope was built by William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse, Knight of the Order of St Patrick was an Irish astronomer who had several telescopes built. His 72-inch telescope "Leviathan", built 1845, was the world's largest telescope until the early 20th century.-Life:He was born in Yorkshire, England, in the city of...
on his estate, Birr Castle
Birr Castle
Birr Castle is a large castle in the town of Birr in County Offaly, Ireland. It is the home of the seventh Earl of Rosse, and as such the residential areas of the castle are not open to the public, though the grounds and gardens of the demesne are publicly accessible.-Ireland's Historic Science...
, at Parsonstown (now Birr
Birr
Birr is a town in County Offaly, Ireland. Once called Parsonstown, after the Parsons family who were local landowners and hereditary Earls of Rosse. It is also a parish in the Roman Catholic Diocese of Killaloe....
in County Offaly
County Offaly
County Offaly is a county in Ireland. It is part of the Midlands Region and is also located in the province of Leinster. It is named after the ancient Kingdom of Uí Failghe and was formerly known as King's County until the establishment of the Irish Free State in 1922. Offaly County Council is...
, Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
).
Construction and Design
Parsons improved the techniques of casting, grinding and polishing large telescope mirrors from speculum metalSpeculum metal
Speculum metal is a mixture of around two-thirds copper and one-third tin making a white brittle alloy that can be polished to make a highly reflective surface. It is used primarily to make different kinds of mirrors including early reflecting telescope optical mirrors...
, and constructed steam-powered grinding machines for parabolic mirrors. His 3 ft (90 cm) mirror of 1839 was cast in smaller pieces, fitted together before grinding and polishing; its 1840 successor was cast in a single piece. In 1842, Parsons cast his first 6 ft (1.8 m) mirror, but it took another five casts, before he had two ground and polished mirrors. Speculum mirrors tarnished rapidly; with two mirrors, one could be used in the telescope while the other was being re-polished. The telescope tube and supporting structure were completed in 1845.
The mirror was 5 in (13 cm) thick and weighed almost 3 tons. This required a mirror cell to support and to prevent the mirror deforming under its own weight. The length of the tube and mirror box is about 54 ft (16.5 m); including the mirror it weighed about 12 tons. The tube is supported at the mirror end by a "universal joint", a hinge with two axes, which allows the tube to be inclined through a large range of altitude and also to be turned through a limited range of azimuth. The azimuth range is limited to about one hour by the supporting walls that flank the tube on its eastern and western sides. The walls are 23 ft (7 m) apart, 40 ft (12 m) high, and 71 ft (21.5 m) long. A chain and counterweight keeps the telescope in balance, another chain with a winch controls the altitude. A rack and pinion
Rack and pinion
A rack and pinion is a type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion. A circular gear called "the pinion" engages teeth on a linear "gear" bar called "the rack"; rotational motion applied to the pinion causes the rack to move, thereby...
beam underneath the tube controls the azimuth. This beam is connected to the eastern supporting wall, where it can move on a circular iron arc to allow the telescope to change altitude.
The tube is of the Newtonian
Newtonian telescope
The Newtonian telescope is a type of reflecting telescope invented by the British scientist Sir Isaac Newton , using a concave primary mirror and a flat diagonal secondary mirror. Newton’s first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope...
design with the eyepiece
Eyepiece
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings...
on its western side. At low altitude, the observer accesses the eyepiece from a wooden gallery that spans the distance between the walls and can slide up and down guides to follow the telescope in altitude. A cage on the gallery moves sideways to reach the eyepiece at different azimuth. At high elevation, curved galleries on top of the western wall are used, which can be moved across the wall to follow the telescope in azimuth.
Operation
The telescope was virtually unused for the first three years, because Parsons was occupied by relief programmes in response to the potato faminePotato famine
Potato famine may refer to:* Great Famine , the famine in Ireland between 1845 and 1852* Highland Potato Famine, a major agrarian crisis in the Scottish Highlands from 1846 to 1857...
.
Charles Messier
Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 110 "Messier objects"...
and John Herschel
John Herschel
Sir John Frederick William Herschel, 1st Baronet KH, FRS ,was an English mathematician, astronomer, chemist, and experimental photographer/inventor, who in some years also did valuable botanical work...
. These catalogues list star clusters as well as nebulae, and the question was whether the latter were merely unresolved star clusters or genuinely nebulous regions of space. If resolved into stars they might be the first galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
to be identified as such. Parsons discovered that several nebulae had a spiral structure, suggesting "dynamical laws". The most notable spiral nebula observed by Parsons was Messier 51
Whirlpool Galaxy
The Whirlpool Galaxy is an interacting grand-design spiral galaxy that is estimated to be 23 ± 4 million light-years from the Milky Way Galaxy. in the constellation Canes Venatici...
, which he resolved into stars.
After William Parsons (the 3rd Earl of Rosse) died in 1867, the 4th Earl (Laurence Parsons
Lawrence Parsons, 4th Earl of Rosse
Lawrence Parsons, 4th Earl of Rosse KP FRS was the son and successor of the astronomer William Parsons, 3rd Earl of Rosse who built the "Leviathan of Parsonstown" telescope, largest of its day, and his wife, the Countess Rosse , an amateur astronomer and pioneering photographer...
) continued to operate the six foot telescope. From 1874 to 1878, J. L. E. Dreyer worked with the telescope and began the compilation of his New General Catalogue of Nebulae and Clusters of Stars
New General Catalogue
The New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...
.
Although the 4th Earl built a smaller 3 ft equatorial
Equatorial mount
An equatorial mount is a mount for instruments that follows the rotation of the sky by having one rotational axis parallel to the Earth's axis of rotation. This type of mount is used for astronomical telescopes and cameras...
in 1876, the six foot telescope remained in use until about 1890. After his death in 1908, the telescope was partly dismantled, and in 1914, one of the mirrors with its mirror box were transferred to the Science Museum
Science Museum (London)
The Science Museum is one of the three major museums on Exhibition Road, South Kensington, London in the Royal Borough of Kensington and Chelsea. It is part of the National Museum of Science and Industry. The museum is a major London tourist attraction....
in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
. The walls remained. The tube, second mirror box, and universal joint survived.
Reconstruction
Following a TV programme, lecture, and book by Patrick MoorePatrick Moore
Sir Patrick Alfred Caldwell-Moore, CBE, FRS, FRAS is a British amateur astronomer who has attained prominent status in astronomy as a writer, researcher, radio commentator and television presenter of the subject, and who is credited as having done more than any other person to raise the profile of...
, there was renewed interest in the six foot telescope in the 1970s. Gradually, the telescope became a visitor attraction. But it was not before the 1990s that plans to actually rebuild the telescope came to fruition. In 1994 the retired structural engineer
Structural engineer
Structural engineers analyze, design, plan, and research structural components and structural systems to achieve design goals and ensure the safety and comfort of users or occupants...
and amateur astronomer
Amateur astronomy
Amateur astronomy, also called backyard astronomy and stargazing, is a hobby whose participants enjoy watching the night sky , and the plethora of objects found in it, mainly with portable telescopes and binoculars...
Michael Tubridy
Michael Tubridy
Michael "Mick" Tubridy is an Irish musician and structural engineer.- Career :In 1962, he was a founder member of the traditional Irish music group, The Chieftains, with whom he played the tin whistle, Irish flute, and concertina. Michael remained a member of the group until 1979.He worked as a...
was called in to research and re-design the Rosse six foot telescope. The original plans were lost, and so it took detective work to review the remains of the telescope, incidental comments in observing logs, and contemporary photographs taken by Mary Rosse
Mary rosse
Mary Rosse, Countess of Rosse , was a British amateur astronomer and pioneering photographer. She was one of the early practitioners of making photographs from waxed-paper negatives.- Life :...
, wife of the 3rd Earl. Reconstruction work lasted from early 1996 to early 1997. It had been planned to include a working mirror, but due to budget constraints this had to be left for a separate project.
The new mirror was installed in 1999. Unlike the speculum
Speculum metal
Speculum metal is a mixture of around two-thirds copper and one-third tin making a white brittle alloy that can be polished to make a highly reflective surface. It is used primarily to make different kinds of mirrors including early reflecting telescope optical mirrors...
original, and unlike modern aluminium- or silver-coated glass mirrors, this is made of aluminium, as a compromise between authenticity and utility in astronomical observation.
Further reading
- Patrick Moore (1981). The Astronomy of Birr Castle. The Tribune Printing and Publishing Group, Birr.
- Patrick Moore (1997). "The Leviathan Reborn". Sky & Telescope, 94.5, p. 52.
- D.H. Levy (2004). "Miracle at Birr Castle". Sky & Telescope, 107.1, p. 84.
- Wolfgang Steinicke. "William Parsons, 3rd Earl of Rosse". Retrieved 22 November 2009.
- Lenny Abbey. "The Earl of Rosse and the Leviathan of Parsontown". The Compleat Amateur Astronomer. Retrieved 23 November 2009.