Keck Observatory

Twin Telescopes


The twin Keck Observatory telescopes are the world’s most scientifically productive optical and infrared telescopes. The telescopes’ primary mirrors are 10-meters in diameter and are each composed of 36 hexagonal segments that work in concert as a single piece of reflective glass.
Extensive computer analysis determined the greatest strength and stiffness for the least amount of steel- about 270 tons per telescope. Each telescope weighs 300 tons and operates with nanometer precision.

Challenges To overcome building new Telescope

Challenge 1: Mirror

The initial idea of a reflecting mirror with a 10- meter diameter (traditional style) but that has several problems: Higher weight, and cost of mirror estimated billion dollars.

To overcome this astronomers need to think of an smart alternative and they did, Astrophysicist Jerry Nelson propose idea of , Instead of a single, gigantic reflecting mirror, constructing a parabolic or bowl-shaped reflecting surface out of many thin mirror segments . But this this he face two major designing challenges : designing a means of keeping the 36 segments perfectly aligned, and finding a way of polishing the segments so that together they would function as a single, giant, parabolic surface.

After 2 years of planning Nelson and his team presented , 6 hexagonal mirror segments arranged in the form of a honeycomb and kept in perfect alignment by a computer-operated active control system. Each mirror segment would be 1.8 meters wide, 7.5 centimeters (about 3 inches) thick, and weigh about half a ton.

Challenge 2: Heat

Heat within a dome (telescope building’s top half circle part) can distort or seriously degrade the images captured by a telescope's primary mirror. To overcome this problem, the dome's interior walls are insulated and covered with a paint chosen for thermal properties that minimize internal heating during the day.

During the day, the interior is air-conditioned, and huge fans can replace all of the air inside the dome every five minutes if necessary . This keeps the indoor and outdoor temperatures nearly identical and ensures that the quality of the mirror's image is limited only by the natural properties of the atmosphere. The thermal design of the dome was studied and optimized by Bill Carroll of LBL's Energy and Environment Division.

How Image is Capture from Telescope

  • Keck telescope capture images on either a Cassegrain or a Nasmyth focus .
  • In the Cassegrain focus,
    light from an object being viewed will be gathered by the mosaic of mirror segments and reflected back toward the prime focal point (5). Before reaching the prime focal point, however, the light will be reflected once again by a small convex secondary mirror, held in a steel frame about 15 meters above the primary mirror(1), back through an opening in the center of the primary mirror (3).
  • In the Nasmyth focus,
    an oblong tertiary mirror is positioned in this opening and it reflects the light from the secondary mirror to foci located on either side of the telescope. (4).

  • There are two secondary mirrors that can be used on the Keck telescope--one for optical studies and one for infrared studies. Whether the telescope is operating as an optical or an infrared instrument, rarely will there be an astronomer peering through an eyepiece at the Keck's images. Instead, images will be recorded by computer-controlled cameras.
  • This is because, to the human eye, a dim object will appear dim no matter how long it is stared at, whereas photographic film, or other types of detectors, exposed to a dim light for a long enough time will produce a bright image. Where the telescope looks will also be computer-controlled. A telephone line linked to the computer allows telescope-pointing instructions to be phoned in.
  • Keck is one of the first telescopes designed for both visible light and infrared viewing, the Keck's infrared capabilities are expected to be far superior to those of any other telescope now in operation. It will make infrared measurements 40 times faster-- meaning it can see much fainter sources of radiation--and produce infrared photos three times sharper than any telescope before.
  • Because Mauna Kea mountain area has dry air, it boost infrared capabilities of observations. Keck telescope, penetrate areas of space too clouded by dust and gas for clear, visible-light sightings. Infrared viewing is particularly useful for finding protesters--stars still in the formation process--that radiate a great deal of heat but are enshrouded in an opaque cocoon of star stuff that makes them appear as smudges to an optical telescope.

the Best Discoveries by Keck Observatories

It helped measure the size of a distant world that is about the size of Uranus.
It uncovered four quasars (galaxies powered by black holes) in a single system.
It found out that a galaxy is almost entirely made of dark matter.
It tracked down interesting atmospheric activity on Jupiter's volcanic moon Io, as well as Neptune.
Exo-Planet hunting.