W. M. Keck Observatory - Overview

Overview

In 1985, Howard B. Keck of the W. M. Keck Foundation gave $70 million to fund the design and construction of the Keck I Telescope. The key advance that allowed the construction of the Keck's large telescopes was the ability to operate smaller mirror segments as a single, contiguous mirror. In the case of the Keck each of the primary mirrors is composed of 36 hexagonal segments that work together as a single unit. The mirrors were made from Zerodur glass-ceramic by the German company Schott AG. On the telescope, each segment is kept stable by a system of active optics, which uses extremely rigid support structures in combination with adjustable warping harnesses. During observation, a computer-controlled system of sensors and actuators adjusts the position of each segment, relative to its neighbors, to an accuracy of four nanometers. This twice-per-second adjustment counters the effect of gravity as the telescope moves, in addition to other environmental effects that can affect the mirror shape.

Each Keck telescope sits on an altazimuth mount. During the design stage, computer analysis determined that this mounting style provides the greatest strength and stiffness for the least amount of steel, which totals about 270 tons per telescope. The weight of each telescope is about 300 tons.

The telescopes are equipped with a suite of instruments, both cameras and spectrometers that allow observations across much of the visible and near infrared spectrum.