It is the largest single optical telescope in the Southern Hemisphere, with a hexagonal mirror array 11 meters across.
Arecibo is the world's largest and most sensitive single telescope for collecting radio signals from space.
A single optical telescope may have an angular resolution less than one arcsecond, but astronomical seeing and other atmospheric effects make attaining this very hard.
At the time of construction in 1987, the WHT was the third largest single optical telescope in the world.
It is a single telescope with the dual abilities.
Silhouetted against the glass that made up the front wall was a single dark telescope on a tripod.
Its main 12-metre array will have fifty antennas, 12 metres in diameter, acting together as a single telescope - an interferometer.
This is because the narrow Cherenkov light cone produced by local muons will only be recorded by a single telescope.
The larger mirrors of single telescopes are still preferred for studying especially faint objects beyond the Milky Way galaxy.
It has a distributed network of small telescopes which together create images of celestial bodies with much higher resolutions than any other single telescope can produce.