The centre section

Either side of the centre section there are two trunnions which allow the main tube assembly to pivot up and down. These trunnions sit on hydrostatic bearings similiar to the ones found in the base box, this keeps the centre section movements very smooth.

The central block, weighing 4 tonnes, is the structure to which the main tube of the telescope is attached. At the bottom end of this tube sits the primary mirror and scientific instruments, while located at the top is the secondry mirror.

The centre section and trunnions are one of the key components of the telescope and help to define the altitude axis of the telescope. On the right you can see this centre section before it is lifted in to place.

In the above image you can see one of the trunnions which help to pivot the centre section. In the background you can see the drive wheel on the opposite side.

This section must be able to cope with the enormous strain of having a 2 metre mirror, weighing over a tonne, at one end, while still being able to move slowly and more importantly smoothly, so as not to distort the images being captured.

To help keep this strength and rigidity, the centre section has been manufactured with an internal structure which helps to stop the flexing that occurs with the weight associated with the main tube assembly.

Here you can see the drive wheel of the centre section. This is used to move the telescope on its altitude axis (if you look closely, you should be able to see the 'teeth' of the cog).

To be able to move such a large component, a drive wheel has been fixed to one side of the centre section. This drive wheel, seen here in the image on the right, moves the centre section to allow the altitude movements to be set and because of the special bearings that the section sits on, it encounters little friction giving it a lot of control over the speed and postion.