THE WORLD'S LARGEST SINGLE MIRROR OBSERVATORY- 10.4 METERS - (MT. PALOMAR IS 5 METERS IN DIAMETER FINISHED IN 1948) WAS JUST DEDICATED ON 2009 JULY 24
The Gran Telescopio Canarias (meaning "Great Canaries Telescope"), also known as GranTeCan or GTC, is a 10.4 m (410 in) reflecting telescope undertaking commissioning observations at the Roque de los Muchachos Observatory on the island of La Palma, in the Canary Islands of Spain, as of July 2009.
Construction of the telescope, sited on a volcanic peak 2,267 metres (7,440 ft) above sea level, took seven years and cost €130 million (£112 million). Its installation had been hampered by weather conditions and the logistical difficulties of transporting equipment to such a remote location. The GTC Project is a partnership formed by several institutions from Spain and Mexico, the University of Florida, and the Instituto de Astrofísica de Canarias (IAC). Planning for the construction of the telescope, which started in 1987, involved more than 1,000 people from 100 companies. As of 2009, it is the world's largest single-mirror optical telescope.
The GTC began its preliminary observations on 13 July 2007, using 12 segments of its primary mirror, made of Zerodur glass-ceramic by the German company Schott AG. Later the number of segments was increased to a total of 36 hexagonal segments fully controlled by an active optics control system, working together as a reflective unit. Its Day One instrumentation were OSIRIS and CanariCam. Scientific observations began properly in May 2009.
The Gran Telescopio Canarias formally opened its shutters on July 24, 2009, inaugurated by King Juan Carlos I of Spain.  More than 500 astronomers, government officials and journalists from Europe and the Americas attended the ceremony, including officials and alumni from the University of Florida. University of Florida Provost Joseph Glover remarked at the opening ceremony that their astronomers get to use the telescope for 20 nights per year because the university invested US$5 million in the project and owns a 5 percent share, even though time on the telescope is highly expensive. The installation of CanariCam, also built by the University of Florida team, will add an additional 35 nights.
The University of Florida's CanariCam, a Day One instrument of GTC (i.e., operational from the start of observations), is a mid-infrared imager with spectroscopic, coronagraphic, and polarimetric capabilities, which will be mounted initially at the Nasmyth focus of the telescope. In the future, when the Cassegrain focus of the telescope is commissioned, it is expected that CanariCam will move to this focus, which will provide superior performance with the instrument. CanariCam is designed as a diffraction-limited imager. It is optimised as an imager, and although it will offer a range of other observing modes, these will not compromise the imaging capability. The fact that CanariCam offers polarimetry and coronagraphy in addition to the more standard imaging and spectroscopic modes makes it a versatile and powerful instrument.
CanariCam will work in the thermal infrared between ≈7.5 and 25 μm. At the short wavelength end the cut-off is determined by the atmosphere; specifically atmospheric water vapour. At the long wavelength end the cut-off is determined by the detector; this loses sensitivity beyond ≈24 μm, although the cut-off for individual detectors varies significantly. CanariCam is a very compact design. It is expected that the total weight of the cryostat and its on-telescope electronics will be under 400 kg. Most previous mid-infrared instruments have used liquid helium as a cryogen; one of the requirements of CanariCam is that it should require no expensive and difficult to handle cryogens. CanariCam will use a two-stage closed cycle cryocooler system to cool the cold optics and cryostat interior down to approximately 28 K (−245 °C; −409 °F), and the detector itself to around 8 K (−265 °C; −445 °F), the temperature at which the detector works most efficiently. CanariCam is expected to be installed in 2010.
Main article: OSIRIS
The IAC's OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy), a Day One instrument of GTC (i.e., operational from the start of observations), is an "imaging and low resolution spectrograph with longslit and multiobject spectroscopic modes. It covers the wavelength range from 0.365 to 1.05 µm with a field of views (FOV) of 7 × 7 arcmin, and 8 arcmin × 5.2 arcmin, for direct imaging and low resolution spectroscopy respectively." It "provides a new generation of instrumental observation techniques such as the tunable filters, the charge-shuffling capability in the CCD detectors, etc."
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