Editing Nordic Optical Telescope

{{short description|Astronomical telescope located at Roque de los Muchachos Observatory}}
{{Infobox telescope|locmapin=Spain Canary Islands}}
[[Image:Not inst 2003.jpg|250px|thumb|The interior of the telescope, showing an instrument on the Cassegrain focus.]]
The '''Nordic Optical Telescope''' ('''NOT''') is an astronomical [[telescope]] located at [[Roque de los Muchachos Observatory]], [[La Palma]] in the [[Canary Islands]]. The telescope saw first light in 1988, and was officially inaugurated during September 1989. Regular observing started in 1990.  It is funded by [[Denmark]], [[Sweden]], [[Norway]], [[Finland]], and (since 1997) [[Iceland]]. Access is provided directly to astronomers of the funding countries, and of all nationalities through international time allocation committees.

The main mirror has a diameter of {{convert|2.56|m|in}}. The optical forming was done at the optical laboratory at the [[Tuorla Observatory]], on mirror blanks made of Zerodur at [[Schott AG|Schott]] Glaswerke in Mainz, Germany.<ref>{{Cite web|url=http://www.not.iac.es/telescope/tti/proptxt.html|title=Nordic Optical Telescope}}</ref>

While the NOT was designed as a passive telescope, with the mirror sufficiently thick to keep its shape even without an active feedback loop, its mirror was designed to be suspended on a pneumatic support system.<ref>{{Cite web|url=http://www.not.iac.es/telescope/tti/proptxt.html|title=Nordic Optical Telescope}}</ref> The designers had planned that this and the flexibility of the mirror would allow for the implementation of a so-called active optics system, a feature that was then under development for [[ESO]]'s [[New Technology Telescope]]. In 1992, such an active optics system was installed at the NOT.<ref>{{Cite journal|url=http://articles.adsabs.harvard.edu//full/1992ESOC...42..311A/0000311.000.html|bibcode = 1992ESOC...42..311A|title = Active Optics on the Nordic Optical Telescope|last1 = Andersen|first1 = T.|last2 = Larsen|first2 = O. B.|last3 = Owner-Petersen|first3 = M.|last4 = Steenberg|first4 = K.|journal = European Southern Observatory Conference and Workshop Proceedings|year = 1992|volume = 42|page = 311}}</ref>

== Instrumentation ==
The NOT operates three instruments that can be mounted -only one at a time- under the Cassegrain focus:
* [http://www.not.iac.es/instruments/alfosc ALFOSC]: a [[CCD camera]] and [[spectrograph]]. This is a versatile instrument that gets most time in the focus. It includes a polarimetry module that allows it to be used for [[polarimetry]] and spectropolarimetry.
* [http://www.not.iac.es/instruments/notcam NOTCam]: a [[infrared camera|near infrared camera]] and spectrograph.
* [http://www.not.iac.es/instruments/mosaic MOSCA]: a 4-CCD mosaic camera, of high efficiency in the blue end of the spectra.

There are two more instruments, permanently mounted on a folded-Cassegrain configuration. Retractable folding mirrors allow to switch in short time from the main instrument to either of them.
* [http://www.not.iac.es/instruments/fies FIES]: a cross-dispersed high-resolution [[Echelle grating|echelle spectrograph]], isolated from thermal and mechanical instability. This is the latest addition to the telescope.
* [http://www.not.iac.es/instruments/stancam StanCam]: a 1 Megapixel [[CCD camera]]. Less sensitive than ALFOSC, and with a smaller field of view, it works as a companion for NOTCam (providing optical photometry), or to react to "target of opportunity" programs when neither ALFOSC nor MOSCA are mounted.

=== Visitor Instruments ===

The NOT has been host to a number of instruments on a "visitor" status.
* [http://www.not.iac.es/instruments/turpol TURPOL]: UBVRI Photopolarimeter. TURPOL has been at the NOT since the very beginning, but it is not available as part of the general instrument set.
* [http://www.not.iac.es/instruments/polcor PolCor]: a combined "Lucky" imager, polarimeter, and [[coronagraph]]
* [http://www.not.iac.es/instruments/luckycam LuckyCam]: High frame rate, low noise [[CCD camera]] for [[lucky imaging]]
* [http://www.not.iac.es/instruments/sofin SOFIN]: High resolution CCD spectrograph. This instrument was first used in 1991, spent many years usefully at the NOT, and was finally decommissioned during 2014.

=== Future ===

A new instrument for the NOT is currently under development, under the working name of NOT Transient Explorer (NTE).<ref name="nte">{{cite web|title=NTE (NOT Transient Explorer)|url=https://nte.nbi.ku.dk|accessdate=15 June 2021}}</ref> This new instrument is intended to be mounted permanently at the Cassegrain focus, providing imaging and spectroscopic capabilities both in the full optical and near-infrared range.

==See also==
[[List of largest optical telescopes in the 20th century]]

==References==
{{Reflist}}

==External links==
{{commons category}}
* [http://www.not.iac.es not.iac.es] - official site.
* [https://www.youtube.com/watch?v=u9Ez5wJK3IY Video] - Video about and at the telescope.

[[Category:Optical telescopes]]
[[Category:Astronomical observatories in La Palma]]