The Mark III was a portable and fully steerable

radio telescope A radio telescope is a specialized antenna (radio), antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the r ...

located at Wardle, near Nantwich,

Cheshire Cheshire ( ) is a Ceremonial counties of England, ceremonial county in North West England. It is bordered by Merseyside to the north-west, Greater Manchester to the north-east, Derbyshire to the east, Staffordshire to the south-east, and Shrop ...

in the north-west of

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

. Constructed in 1966, it was remotely controlled from

Jodrell Bank Observatory Jodrell Bank Observatory ( ) in Cheshire, England hosts a number of radio telescopes as part of the Jodrell Bank Centre for Astrophysics at the University of Manchester. The observatory was established in 1945 by Bernard Lovell, a radio as ...

, and was mainly used as part of the MERLIN radio telescope network. It was designed by Charles Husband at the instigation of Bernard Lovell.Lovell, ''Jodrell Bank Telescopes'', p. 12

Technical specifications

Funding for the telescope was obtained in 1963 from the DSIR. The telescope was designed by Husband and Co. consulting engineers, and was constructed by Fairey Engineering. It started observations in July 1967. The telescope could be controlled either locally, or by remote control over UHF and microwave links from

(normally the latter).Palmer and Rowson (1968) Similar to the Mark II, it had an elliptical dish with a major axis of 125 ft/38.1m and a minor axis of 83 ft 4 in/25.4m. Unlike the Mark II, however, the dish is constructed of a wire mesh, with the wires apart set to an accuracy of . When pointed to the horizon, the telescope was 81% efficient at wavelengths of 21 cm (the hydrogen line), dropping to 45% at 11 cm. When the bowl was pointed to the horizon, the structure deformed slightly under gravity, meaning that the telescope becomes 14% efficient at 11 cm. The focus cabin was an ~8 foot cube, also similar to the Mark II, supported by four steel girders. It could be accessed via a ladder up one of the girders, which could be climbed when the bowl of the telescope was directed towards the horizon. The telescope was steered in

azimuth An azimuth (; from ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. Mathematically, the relative position vector from an observer ( origin) to a point ...

and

elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...

by hydraulic drive systems. Two of the six bogies on which the telescope sat were driven, and motion in elevation was done using two long hydraulic

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder (engine), cylinder a ...

s. Both were driven by a 5 horse power electric motor, at up to 5 degrees per minute. The drive system was protected using over-pressure alarms, cut-outs and relief valves, as well as two alarms (one at the telescope, one at Jodrell). The main aim for the telescope when constructed was to use it in conjunction with the

Lovell Telescope The Lovell Telescope ( ) is a radio telescope at Jodrell Bank Observatory, near Goostrey, Cheshire, in the north-west of England. When construction was finished in 1957, the telescope was the largest steerable dish radio telescope in the world a ...

as a fully steerable interferometer to determine the sizes of radio sources. It was not known what size the radio sources would be, and so the optimal telescope separation was not known (the separation is inversely proportional to the resolution of the interferometer). As a result, the telescope was built such that it could be completely disassembled and reassembled on a new site within 6 months. The baseline between the telescope and the

was 24 km, giving a resolution ranging between 0.2 and 17 arcseconds depending on the frequency that was being observed at. In 1996, it was decommissioned due to its age and lack of sensitivity compared with modern telescopes. It was subsequently dismantled and sold for scrap.

References and further reading

Books

Journal articles

{{Jodrell Bank Observatory Jodrell Bank Observatory Buildings and structures in Cheshire Radio telescopes