The dome is the ‘shell’ that will cover the telescope and protect it – like a snail’s shell. A rotating steel structure, the dome, together with the upper part of the enclosure base, will house the telescope chamber.
Shaped like a spherical helmet, the dome will have a diameter of 34 m and be almost 24 m high at its tallest point – as high as an eight-storey building. It will consist of a lattice framework covered on the outside by a spherical layer of cladding and on the inside by thermal insulation. The whole 500 tonne structure will rest on tracks at its base so that it can rotate on its axis of vertical symmetry.
So that the telescope can observe, the GTC’s dome will have a 13 m wide slit with two mobile shutters. These will be sliding doors – a large upper shutter that will always slide away to the back and a smaller one that will generally slide downwards but can also slide up to allow observation near to the horizon.
The dome will have apertures to help keep the temperature uniform throughout the telescope, ensuring good image quality.
Lastly, there will be one other moving part – a folding metal wind screen to keep the effect of the wind on the telescope to a minimum. It will be situated under the shutters of the dome slit.