Editing New Technology Telescope (section)

== Characteristics ==

[[Image:ESO-New Technology Telescope-phot-07b-07.jpg|thumb|left|upright=0.75|ESO's New Technology Telescope at La Silla]]

The main mirror of NTT is flexible and its shape is actively adjusted during observations by actuators to preserve the optimal image quality. The secondary mirror position is also actively controlled in three directions. This technology, developed by ESO, known as active optics, is now applied to all major modern telescopes, such as the [[Very Large Telescope]] at Cerro Paranal and the future European [[Extremely Large Telescope]]. The design of the octagonal enclosure housing the NTT is another technological breakthrough. The telescope dome is relatively small, and is ventilated by a system of flaps that makes air flow smoothly across the mirror, reducing turbulence and leading to sharper images.<ref>{{cite web|url=http://www.eso.org/public/teles-instr/lasilla/ntt.html|title=The New Technology Telescope (NTT)|accessdate=2011-05-19}}</ref>

The NTT was the first telescope using what is now known as active optics: a feedback loop that actively keeps the (comparatively thin) monolithic mirror in shape, using numerous actuators on which the mirror is mounted.<ref>R. N. Wilson, https://www.eso.org/sci/publications/messenger/archive/no.113-sep03/messenger-no113-2-9.pdf</ref>

Its design as well as the design of its enclosure (the building protecting it) included many revolutionary features, from whence it was named. In particular, great care was taken to ensure a good ventilation of the telescope, and to avoid heat sources in around the telescope. Since its construction, the NTT has undergone several upgrades which continued to improve its quality. It was used as a real-life test bench for the engineering concepts and software used for the [[Very Large Telescope]].

The New Technology Telescope initially had the same problem as the [[Hubble Space Telescope]] - the mirror was ground to the wrong shape due to a mis-calibrated [[null corrector]]. However, the active optics system of the NTT was able to correct that error without refiguring the mirror.<ref>{{cite news |title= Panel Finds Error by Manufacturer of Space Telescope |author=William J. Broad |work=[[New York Times]] |date=1990-08-10 |url=https://www.nytimes.com/1990/08/10/us/panel-finds-error-by-manufacturer-of-space-telescope.html}}. Mentions null corrector error that happened during the manufacture of the New Technology Telescope, and the correction by the active optics system.</ref>