Hale Telescope mirror.. It was completed in 1948 and is still in active use. The Hale Telescope represented the technological limit in building large optical telescopes for over 30 years. It was the largest telescope in the world until the Russian BTA-6 was built in 1976, and the second largest until the construction of the Keck Observatory Keck 1 in 1993. Hale supervised the building of the telescopes at the Mount Wilson Observatory with grants from the Carnegie Institution of Washington: the telescope in 1908 and the telescope in 1917. These telescopes were very successful, leading to the rapid advance in understanding
VISTA (telescope) and is by far the largest telescope in the world dedicated to surveying the sky at near-infrared wavelengths. The telescope has only one instrument: VIRCAM, the Vista InfraRed CAMera. This is a 3-tonne camera containing 16 special detectors sensitive to infrared light, with a combined total of 67 million pixels. A second-generation instrument called 4MOST, a 2400-object fibre-fed multi-object spectrograph, is under development for installation around 2020. Observing at wavelengths longer than those visible to the human eye allows VISTA to study objects that may be almost impossible to see in visible light because they are cool, obscured by dust