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Proceedings Paper

High-resolution incremental tape encoder on the William Herschel Telescope
Author(s): Martin Fisher
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Paper Abstract

Large, modern optical telescopes demand high performance pointing and tracking of the mount unless alternative methods of correcting the telescope `beam' are to be completely relied upon. This is rarely the case and `open-loop' specifications are still very demanding. The move from precision-geared to friction driven axes has excluded the use of gear-driven encoders while friction-driven encoders have not proved successful. Fiber and laser gyros are not sufficiently developed for use as a primary encoding system although they have useful inertial properties for inclusion in some systems. Tape encoders, which have been around for a very long time, are the major contender for today's applications. A commercially available inductive tape encoder system has been fitted to the 4.2 m William Herschel Telescope in order to properly evaluate its performance and hence its suitability for use with the 8 m Gemini telescopes. The encoder system and the method adopted for fitting it to an operational telescope is briefly described and the results from performance tests are presented. Subsequent investigations into sources of error and the desirability and methods of correcting them are discussed and future work is considered.

Paper Details

Date Published: 1 June 1994
PDF: 12 pages
Proc. SPIE 2199, Advanced Technology Optical Telescopes V, (1 June 1994); doi: 10.1117/12.176262
Show Author Affiliations
Martin Fisher, Royal Greenwich Observatory (United Kingdom)

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

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