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Proceedings Paper

Study of a 25-m telescope for optical wavelengths
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Paper Abstract

A study of a 25 m class telescope is presented. The scientific case is described together with imaging and spectroscopy aspects. Spectroscopy is found possible also at high resolution with the telescope proposed. Light efficiency and mirror coating are discussed. The optical design and corresponding performance requirements are presented. With a spherical segmented f/0.9 primary mirror and an exit focal ratio of f/2.86, an on-axis four mirror system with segmented primary and quaternary mirrors is found optimal. It gives an image quality of 0.27 arcsec FWHM over a field of 90 arcsec. Mechanical design is based on a tripod configuration similar to those of radio telescopes. The alignment system proposed is discussed. Total alignment is divided into three main sub-tasks. First, low frequency alignment is established using a slow wavefront sensor. Second, a high frequency alignment is maintained with an internal laser measurement system. Third, a high frequency correction for wavefront tilt errors is made with a correlation tracker. The enclosure is co-rotating with two sections sliding apart for observations. It has adjustable wind screens and double skin panels with internal air circulation. Control facilities are installed in a thermal jacket and the observing floor is cooled.

Paper Details

Date Published: 1 June 1994
PDF: 19 pages
Proc. SPIE 2199, Advanced Technology Optical Telescopes V, (1 June 1994); doi: 10.1117/12.176199
Show Author Affiliations
Arne L. Ardeberg, Lund Observatory (Sweden)
Torben Andersen, Nordic Telescope Group (Denmark)
Mette Owner-Petersen, Nordic Telescope Group (Denmark)

Published in SPIE Proceedings Vol. 2199:
Advanced Technology Optical Telescopes V
Larry M. Stepp, Editor(s)

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