William Herschel Telescope
The WHT has a 4.2 metre primary mirror. It was built in 1987. At that time it was the third largest optical telescope in the world. Today it would be classed as a medium-size telescope. The WHT still produces world-class science using its state-of-the-art science tools.
The WHT observes visible and infra-red wavelengths of light. The WHT was used to find the first evidence for a supermassive black hole in the centre of the Milky Way. It was also the first optical telescope to observe a gamma-ray burst.
The WHT is a complex piece of machinery. Scientists and engineers need to be close by in case any of its systems break. The observatory includes a 3-story building which includes offices, computer rooms, and a kitchen. Astronomers using the telescope spend their nights in the control room. The building also contains an aluminising plant. This is used to replace the mirror's surface every couple of years. This is done to remove any dust or dirt which has built up over time. The mirror must be clean to collect as much light as possible.