The Dome and the Building of the William Herschel Telescope
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William Herschel Telescope

The Dome and the Building

The dome, which weighs 320 tonnes, was completed by the Canadian firm Brittain Steel in 1984. Large fabrications were assembled in Vancouver and shipped to La Palma where they were erected to form the ring girder carrying the transport system and the arch girder which supports the shutters and wind shield.  The skin of the dome was fabricated on site from 6.3 mm steel plate and the wind shield and shutters were constructed from aluminium alloy. A 35 tonne crane, supported from the arch girder, is built into the upper part of the dome. This was used during the telescope construction, and it still remains in place to remove the mirror for aluminizing and for telescope maintenance.

The telescope is supported by a reinforced concrete pier which puts the centre of rotation of the telescope at a height of 13.4 m above the ground. The dome is onion-shaped, of 21 m internal diameter, and a pair of up-and-over shutters with a windscreen coupled to the lower shutter allows observations down to 12 degrees above the horizon. The dome is supported on a rail set onto a cylindrical concrete building structure which internally is open to ground level. Set on one side of the cylindrical drum is a 3-storey rectangular annex of conventional construction. This contains the mirror aluminizing plant, the operations control room, computer room, dark rooms, workshops, offices and various services. Because no unnecessary activity takes place in the dome there is very little thermal disturbance of the air near the telescope, which greatly improves the chance of achieving perfect 'dome seeing'. This is further facilitated by large extractor fans set into the cylindrical structure.

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Last modified: 23 July 2015