Gemini North telescope

Photograph of Gemini North telescope


The International Gemini Observatory consists of twin 8.1-meter diameter optical/infrared telescopes located on two of the best observing sites on the planet. The North telescope is located on Hawaii‘s Maunakea as part of the international community of observatories built to take advantage of the superb atmospheric conditions on this long-dormant volcano which rises about 4214 meters (13,825 feet) into the dry, stable air of the Pacific. Both of the Gemini telescopes have been designed to excel in a wide variety of optical and infrared capabilities. By incorporating technologies such as laser guide star adaptive optics and multi-object spectroscopy, astronomers in the Gemini partnership explore the universe in unprecedented depth and detail. The Gemini Observatory's international headquarters is located in Hilo, Hawai‘i at the University of Hawaii Hilo's University Park.

Gemini’s twin telescopes are optimized for observing in the mid-infrared with silver-coated mirrors, an extremely light structure for the secondary, and a light baffle (used when observing in the optical) which can be closed for observing in the infrared. The mirrors are f/1.8, 8.1 m diameter, 20 cm thick meniscus, and weighs 22,200 kg. Each was made from 55 blocks of low expansion (ULE-581) glass fused together at 1700 degrees C and slumped at Corning's Canton, New York facility. Each mirror blank was then shipped to REOSC Optique in Paris, France, for polishing of its reflecting surface to that of a concave hyperboloid. The measured surface accuracy is 15.6 nm (rms).

The Gemini telescopes have a suite of 4 optical and infrared, imagers and spectrographs, mounted on the back of the telescopes at the same time (as well as the acquisition and guidance instruments). This means that switching from one instrument to another takes a matter of minutes to complete before being capable of taking data on the next science target.

The Gemini North telescope is one of several telescopes near the summit (or in the summit area) of Maunakea, which is considered spiritual by a portion of the native Hawaiian community. 

Gemini is also unique among other 8-10 meter class observatories in that the telescopes can be (and usually are in the case of Gemini North) operated fully remotely from our base facilities.

Since 2002 Gemini North has also been known as the Frederick C. Gillett Gemini North telescope

Travel information for Gemini North is available here.

For scientists: More details can be found on the science telescope page.


Gemini North telescope

Name(s) Gemini North 
Status Operational
Broad Science Goals
  • Twin telescopes in both hemispheres provide participant members with access to the entire sky
  • To provide the best image quality possible from the ground for telescopes of their size.
  • To provide the cleanest possible (i.e. lowest possible emissivity) telescopes, for optimal infrared observing from the ground.

The Gemini Observatory is a world-leader in wide-field adaptive optics assisted infrared imaging, and supports research in almost all areas of astronomy.

Site Maunakea, Hawai‘i, USA
Location Coordinates 19º49.4’N
Altitude 4214 meters (13,825 ft)
Enclosure 46-meter rotating dome
Type Optical/Infrared telescope
Optical Design Ritchey-Chretien Cassegrain
Field of View Maximum 10 arcminutes diameter on the bottom port, and 7 arcminutes diameter on the side ports due to science fold mirror size
Diameter: Primary M1 8.1 meters
Material: Primary M1 Corning Ultra-Low Expansion (ULE) Glass
Diameter: Secondary M2 1.0 meter
Material: Secondary M2  
Mount rapid tip-tilt and chopping mechanism
First Light Date 1999
Adaptive Optics AO system, ALTAIR, has been offered at Gemini North since 2003 and is now available for use with both natural and laser guide stars with NIRI and NIFS.
Images taken with the Gemini North telescope Link
Images of the Gemini North telescope Link
Videos of the Gemini North telescope Link
Press Releases with the Gemini North telescope Link

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