The Mark III was a portable and fully steerable radio telescope located at Wardle, near

Nantwich Nantwich ( ) is a market town and civil parish in the unitary authority of Cheshire East in Cheshire, England. It has among the highest concentrations of listed buildings in England, with notably good examples of Tudor and Georgian architecture. ...

, Cheshire in the north-west of

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. 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 astro ...

, and was mainly used as part of the MERLIN radio telescope network. It was designed by

Charles Husband Sir Henry Charles Husband (30 October 1908 – 7 October 1983), often known as H. C. Husband, was a leading British civil and consulting engineer from Sheffield, England, who designed bridges and other major civil engineering works. He is particul ...

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 Department of Scientific and Industrial Research, abbreviated DSIR was the name of several British Empire organisations founded after the 1923 Imperial Conference to foster intra-Empire trade and development. * Department of Scientific and Industria ...

. 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 Mark II or Mark 2 often refers to the second version of a product, frequently military hardware. "Mark", meaning "model" or "variant", can be abbreviated "Mk." Mark II or Mark 2 may refer to: Military and weaponry * 16"/50 caliber Mark 2 gun ...

, 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 The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , w ...

), 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 ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematical ...

and

elevation The elevation of a geographic 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 surface (see Geodetic datum § Ver ...

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 pistons. Both were driven by a 5

horse power Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the ...

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 at ...

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 A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The ...

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