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Observatorio del Roque de los Muchachos


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Nordic Optical Telescope (NOT)
Image of the NOT
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The Nordic Optical Telescope (NOT) is a modern 2.6-m optical/IR telescope, located at the highest site of the Roque de los Muchachos Observatory. Inaugurated in 1989, NOT is operated by a consortium of Research Councils from Denmark, Finland, Norway, and Sweden, and the University of Iceland.

NOT serves the astronomical communities of these countries and Spain, but all astronomers may apply for time at NOT. All proposals are peer reviewed by an independent committee, and competition for time is keen.

NOT also participates in the OPTICON Trans-National Access programme for all European astronomers, funded by the EU Commission under Framework Programme 6.

An audiovisual about the telescope is available here.


NOT is equipped with a set of instruments designed to optimise its performance on projects where it can be fully competitive. The workhorse optical camera/ spectrograph combination ALFOSC offers a wide and flexible set of observing modes; direct imaging and single- as well as multi-object spectroscopy are available simultaneously. A unique, multi-window high-speed readout mode allows to monitor rapid brightness variations in a target star, as referred to several comparison stars measured simultaneously.

NOTCam is a near-IR counterpart to ALFOSC, and both are in much demand for programmes ranging from cosmology to the Solar system. Two high-resolution échelle spectrographs, SOFIN and FIES, supplement them for detailed work on bright objects; FIES is fed by an optical fibre, making it permanently available for a wide range of projects requiring flexible scheduling.

For direct imaging, a 4096x4096-pixel mosaic CCD camera provides maximum sensitivity of any camera at the observatory, while a standby CCD camera provides instant optical imaging at all times. This allows NOT to react immediately to new discoveries, regardless of other ongoing programmes - another NOT specialy.
Observations may be conducted by the visiting astronomers as well as in service mode, i.e. by the NOT staff. All NOT instruments are being provided with pipeline reduction software for quick-look data quality assessment at the telescope, as well as for the final data reduction needed for the scientific analysis.


The primary mirror of NOT is 2.6 m in diameter. The telescope moves on vertical and horizontal axes, under full computer control. The light-weight, building rotates together with the telescope itself. NOT is designed for high-quality optical and near-infrared imaging, so the optical surfaces are of very high quality and can be tuned to optimum performance. The building is designed to avoid all disturbing heat sources, and the dome is cooled during daytime. Through wide shutters, the dome is flushed with ambient air at the beginning of the night - a feature adopted by all later telescopes.

Because of these features and its ideal location at the site, NOT consistently delivers the best images of any night-time telescope at ORM. As far as possible, observations are scheduled to take advantage of the best observing conditions.


A medium-size telescope cannot be competitive in all fields, but must focus on the strengths of its user community. The science at NOT reflects this.

In cosmology, NOT contributes a string of new results on the visible afterglows of the enigmatic gamma-ray bursts, the most powerful explosions currently seen in the universe. It also contributes to the study of Type Ia supernovae, the 'standard candles' that revealed a mysterious 'dark energy' which drives the expansion of the universe. These and other projects use NOT data together with observations from space at other wavelengths.

A NOT specialty in the study of stars is multi-year spectroscopic monitoring of spots and magnetic fields on the surfaces of solar-like active stars. High-speed photometry with ALFOSC has also led to the detection of many new pulsating stars, shedding light on their internal structure by the novel technique of asteroseismology.

Finally, the exquisite image quality of NOT has been used to study bodies in the solar system, from the surface of Mercury to the detection of new moons of Uranus and Neptune. Indeed, some of the latter have been named after Nordic gods in recognition of NOT's role in detecting them and measuring their orbits. The orbits and shapes of asteroids that might impact on Earth sometime in the future are also measured with NOT.


NOT was conceived as a self-contained facility like many others, and it has served well in this role. But astronomy is changing rapidly, and so is the world: Most of NOT's user community now has access to 8-m-class telescopes, and front-line projects often involve the entire sky and observations at all wavelengths. A medium-size telescope like NOT must constantly re-think its role in this situation.

Future science at NOT will focus on specialised Nordic research fields where NOT can deliver unique services. An increasingly important role will be in training young astronomers and engineers. NOT's easy-to-learn operation and informal, hands-on style is well suited for this, collaborations between the user communities. A NOT Research Student program provides support for students who want to get their hands into real observing. NOT is also used for shorter training courses - some even in remote mode from Nor-dic institutes.

A long-term plan is in preparation to operate NOT and some other telescopes as a unit, with greater scientific power and even more cost-effective in operation.

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