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Subaru (telescope)

Subaru Telescope
The Subaru Telescope
Organization National Astronomical Observatory of Japan
Location Mauna Kea, Hawai'i, USA

19°49′32″N 155°28′36″W / 19.82556°N 155.47667°W / 19.82556; -155.47667Coordinates: 19°49′32″N 155°28′36″W / 19.82556°N 155.47667°W / 19.82556; -155.47667

Altitude 4139 m[1]
Wavelength Optical/Infrared
Built Completed 1998
Telescope style Cassegrain
Diameter 8.3 m[2] (8.2m usable)
Secondary dia. 1330/1400/1265 mm[3]
Angular resolution 0.23″[3]
Collecting area ~53 m²
Focal length f/1.83 (15.000 m)[3]
Mounting altitude/azimuth
Dome cylindrical

Subaru Telescope (すばる望遠鏡 Subaru Bōenkyō?) is the 8.2 metre flagship telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii. It is named after the open star cluster known in English as the Pleiades. It had the largest monolithic primary mirror in the world from its commission until 2005.[4]


Subaru is a Ritchey-Chretien reflecting telescope. Instruments can be mounted at a Cassegrain focus below the primary mirror, in enclosures on either of two Nasmyth focal points on the sides of the telescope mount, to which light can be directed with a tertiary mirror, or, in an arrangement rare on large telescopes, at the prime focus, in lieu of a secondary mirror, to provide a wide field of view suited to deep wide-field surveys.[5]

In 1984, the University of Tokyo formed an engineering working group to study the concept of a 7.5-metre telescope. In 1985, the astronomy committee of Japan's science council gave top priority to the development of a "Japan National Large Telescope" (JNLT), and in 1986, the University of Tokyo signed an agreement with the University of Hawaii to build the telescope in Hawaii. In 1988, the National Astronomical Observatory of Japan was formed through a reorganization of the University's Tokyo Astronomical Observatory, to oversee the JNLT and other large national astronomy projects.[3]

Construction of the telescope began in April 1991, and later that year, a public contest gave the telescope its official name, "Subaru Telescope." Construction was completed in 1998, and the first scientific images were taken in January 1999.[6] In September 1999, Princess Sayako of Japan dedicated the telescope.[7]

A number of state-of-the-art technologies were worked into the telescope. For example, 261 computer-controlled actuators press the main mirror from the back to correct its distortion when the telescope changes its orientation. The telescope enclosure building is also shaped to minimize air turbulence, to improve the quality of astronomical images.

Subaru is one of the few state-of-the-art telescopes to have ever been used with the naked eye. For the dedication, an eyepiece was constructed so that Princess Sayako could look through it directly. It was enjoyed by the staff for a few nights until it was replaced with the much more sensitive working instruments.[8]

Accidents during construction

Two separate incidents claimed the lives of four workers during the construction of the telescope. On October 13, 1993, 42-year-old Paul F. Lawrence was fatally injured when a forklift tipped over onto him. On January 16, 1996, sparks from a welder ignited insulation which smoldered, generating noxious smoke that killed Marvin Arruda, 52, Ricky Del Rosario, 38, and Warren K. "Kip" Kaleo, 36, and sent twenty-six other workers to the hospital in Hilo. All four workers are memorialized by a plaque outside the base of the telescope dome and a sign posted temporarily each January along the Mauna Kea access road.[9]

Mishap in 2011

On July 2, 2011, the telescope operator in Hilo noted an anomaly from the top unit of the telescope. Upon further examination, coolant from the top unit was found to have leaked over the primary mirror and other parts of the telescope.[10] Observation using Nasmyth foci resumed on July 22, and Cassegrain focus resumed on August 26.[11]


Several cameras and spectrographs can be mounted at Subaru Telescope's four focal points for observations in visible and infrared wavelengths.

Multi-Object Infrared Camera and Spectrograph (MOIRCS) 
Wide-field camera and spectrograph with the ability to take spectra of multiple objects simultaneously, mounts on the Cassegrain focus.
Infrared Camera and Spectrograph (IRCS) 
Used in conjunction with the new 188-element adaptive optics unit (AO188), mounted at the infrared Nasmyth focus.
Cooled Mid Infrared Camera and Spectrometer (COMICS) 
Mid-infrared camera and spectrometer with the ability to study cool interstellar dust, mounts on the Cassegrain focus.
Faint Object Camera And Spectrograph (FOCAS) 
Visible-light camera and spectrograph with the ability to take spectra of up to 100 objects simultaneously, mounts on the Cassegrain focus.
Subaru Prime Focus Camera (Suprime-Cam) 
80-megapixel wide-field visible-light camera, mounts at the prime focus.
High Dispersion Spectrograph (HDS) 
Visible-light spectrograph mounted at the optical Nasmyth focus.
Fiber Multi Object Spectrograph (FMOS
Infrared spectrograph using movable fiber optics to take spectra of up to 400 objects simultaneously. Mounts at the prime focus.
High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) 
Infrared camera for hunting planets around other stars. Used with AO188, mounted at the infrared Nasmyth focus.

Hyper Suprime-Cam, a 900-megapixel ultra-wide-field camera, is being built as of late 2011, with first light planned for the end of January 2012.[12] The extremely large wide-field correction optics (a seven-element lens with some elements up to a metre in diameter) was manufactured by Canon and delivered March 29, 2011.[13] It will be used for surveys of weak lensing to determine dark matter distribution.

See also


External links

  • Official website for Subaru Telescope
  • National Astronomical Observatory of Japan
  • Micro-lens for Subaru Telescope
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