General Information on the William Herschel Telescope
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William Herschel Telescope

General Information

The William Herschel Telescope (WHT) was the third largest single-mirror telescope in the world, when completed in July 1987.

To combine the achievement in telescope construction and the new prospects for observation with a reference to the telescope mounting and the Kingdom of Spain, it was decided to name the telescope after Sir William Herschel. It was he who used an altazimuth mount to allow the construction of telescopes with unprecedented power, one of which, and possibly the best, was delivered to Madrid Observatory in 1803.

Installation of the telescope started in the autumn of 1985 when a part shipment containing the azimuth bearings and the hydraulic pumping system arrived on site from the UK. RGO staff who formed the installation team then started the critical job of installing the azimuth bearings and the plant. The bearings were then grouted in place by a contractor using a special epoxy grouting system designed to maintain maximum stiffness between the bearings and the concrete pier.

The major shipment of all the remaining telescope components including the drive system, mirrors and aluminizing plant was arranged for the spring. The M.V. Ston was chartered earlier because of the special facilities on the ship for lifting heavy loads. It sailed on 2 April 1986, arriving in La Palma eight days later. Pickfords then transported the major parts of the telescope, which totalled 350 tonnes, to site over the next four weeks. Some of the loads were very large, 6 × 8 metres and weighing 30 tonnes. These presented the haulage contractor with a number of difficult problems negotiating the very tight bends and steep gradients on the mountain road.

Installation started as soon as loads began to arrive on site and very good progress was made by the RGO team and its subcontractors during the rest of 1986. The installation of the cables and control room progressed in parallel, and commissioning using the telescope control computer started in March 1987. The mirror was aluminized in May and installed in the telescope shortly afterwards.

The azimuth and altitude bearings were the first major items to be commissioned and initial tests indicated that the design natural frequency of 4 Hz for the structure and bearings had been achieved in practice. This justified the careful mechanical design and analysis the RGO put into the telescope and eased the task of the servo control system and software design.

The optical telescope assembly weighs 79,513 kg and including the mounting 186,250 kg.

The budget for the design, erection and manufacture of the WHT, its control system, dome, building, aluminizing tank and other plants, and a full set of instrumentation was £15 million (October 1984 prices). 

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Last modified: 13 December 2010