The Keck telescope, located in Mauna Kea, is currently the largest telescope in the world. It consists of two telescopes each having a 10m diameter.
In 1977 the University of California formed a five-member committee to come up with a design for a 10m telescope, thus doubling the diameter of the Hale Telescope. The main problem this team faced is the fact that a 10m mirror would have an exorbitant cost - it would have be to be immensely strong (and hence thick) not to bend under its own weight. It was estimated that such a mirror would cost approximately $1 billion, an impossible amount for a science team to find. Out of this committee, under the auspices of the University of California and Caltech, was born CARA (California Association for Research in Astronomy) the association that still is responsible for the operation of the telescope.
Jerry Nelson, an experimentalist with a background in particle physics and a member of the committee, came up with a radical design concept for the new telescope. Why not build it out of a whole lot of little mirrors arranged to simulate one big mirror? Together with physicist Terry Gast and engineer George Gabor they developed a design for a segmented mirror consisting of 36 1.8m six-sided mirrors. The combined weight of these mirrors would then be equivalent to the 5m mirror used in the Hale telescope.
On their way to finalising the design they developed specialised techniques to:
- Polish the mirrors - by essentially stretching and apply forces to the mirror in order to warp it to such an extent that when they polished it, it had the right curvature.
- Align the segments - by placing edge sensors on each mirror that calculated the misalignment between each segement and use a computer system to correct for this.
Now with a reasonable budget and design they received funding ($70 million) from the W.M. Keck Foundation in Los Angeles to start the project. The site on Mount Kea was chosen, mainly due to its altitude (13779 feet) and the low light polution, and construction started on September 12, 1985.
On October 12, 1990 the first mirror segment was installed and on December 4 the telescope captured it's first light. The telescope was officially dedicated on November 7, 1991 and completed on April 14, 1992.
The revolutionary idea to design huge telescopes without having to construct enormous mirrors has lead to several similar telescopes being constructed, or under construction, across the world. Some of these include:
- Location: Mauna Kea, Hawaii USA
- Height above sea level: 4205 meters
- Longitude: 155° 28' W
- Latitude: 19° 49' N
- Moving mass: 270 tonnes
- Mirror diameter: 10 meters
- Focal Ratio: f/1.75, 15, 25 IR
- Mount: altazimuth