Editing Active optics (section)

{{Short description|Shaping technology for reflecting telescopes}}
[[Image:GTC Active Optics Acutators.jpg|thumb|right|Actuators of the active optics of the ''[[Gran Telescopio Canarias]]''.]]
'''Active optics''' is a [[technology]] used with [[reflecting telescope]]s developed in the 1980s,<ref>{{cite journal|last=Hardy|first=John W.|title=Active optics: A new technology for the control of light|date=June 1977|series=Proceedings of the IEEE|pages=110|url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA339170|bibcode=1978IEEEP..66..651H|journal=IEEE Proceedings|volume=66|access-date=2011-06-01|archive-url=https://web.archive.org/web/20151222112555/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA339170|archive-date=2015-12-22|url-status=dead}}</ref> which actively shapes a telescope's [[mirror]]s to prevent deformation due to external influences such as wind, temperature, and mechanical stress. Without active optics, the construction of 8 metre class telescopes is not possible, nor would telescopes with segmented mirrors be feasible.

This method is used by, among others, the [[Nordic Optical Telescope]],<ref>{{cite conference|last=Andersen|first=T.|author2=Andersen, T.|author3= Larsen, O. B.|author4= Owner-Petersen, M.|author5= Steenberg, K.|title=Active Optics on the Nordic Optical Telescope|conference=ESO Conference and Workshop Proceedings|date=April 1992|series=Progress in Telescope and Instrumentation Technologies|pages=311–314|editor1-first=Marie-Helene|editor1-last=Ulrich|bibcode=1992ESOC...42..311A}}</ref> the [[New Technology Telescope]], the [[Telescopio Nazionale Galileo]] and the [[Keck telescope]]s, as well as all of the largest telescopes built since the mid-1990s.

Active optics is not to be confused with [[adaptive optics]], which operates at a shorter timescale and corrects atmospheric distortions.