James Clerk Maxwell Telescope - Technical Details

Contents

Introduction

The JCMT is a 15-m diameter telescope optimised for observations at sub-millimeter wavelengths, situated close to the summit of Mauna Kea, Hawaii. Although the JCMT is a partnership between the United Kingdom, Canada and the Netherlands in accordance with the site agreement with the University of Hawaii, proposals can be accepted from individuals and groups of any nationality.

Photo (above right): The JCMT sub-mm telescope primary mirror seen from behind

Telescope and Site Properties

2.1 Basics

The James Clerk Maxwell Telescope has an alt-azimuth mounting, and is engineered according to the principle of homologous deformation¹ to maintain a paraboloid at all elevations. It is housed in a dome, or "carousel", which is physically unattached to the antenna, but co-rotates with the latter. To protect the antenna and associated equipment from the elements, the carousel has both large doors and a sliding roof, which are stowed during operation. Under normal observing conditions, a Gortex membrane transparent to mm- and submm-waves is in place, protecting the telescope from exposure to the sun, wind, and dust. On account of the presence of the membrane the JCMT is the only mm/submm telescope capable of routinely observing the Sun directly, although this results in distortion of the telescope surface, very significantly affecting the beam shape and efficiency at frequencies above about 350 GHz.

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