China's 500m aperture spherical telescope, named Fast, pictured at three different assembly stages in Pingtang County, south-west Guizhou province.

The topmost photo was taken in August last year, the second in December, and the third on Wednesday.

Fast, the world's largest radio telescope, is about the size of 30 football pitches and has a dish-like reflector, made up of 4,450 panels.

Technicians have now assembled 99.8 per cent of the panels and work on the reflector will be completed on Sunday.

The telescope will be used to detect and collect signals and data from the universe.