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Title: Experiments with the Cambridge Optical Aperture Synthesis Telescope
Author: Burns, D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1997
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The Cambridge Optical Aperture Synthesis Telescope, or COAST, was conceived by Baldwin and co-workers at the Cavendish Laboratory in 1987 as the simplest possible separated element array for optical closure phase imaging. At the outset if was not clear that the technical difficulties associated with co-phasing the multiple elements simultaneously could be overcome. In this dissertation I describe work which spans the transition between the "engineering and construction" phase and the "astronomical" phase of the COAST project. The contents of each Chapter are as follows: • In Chapter 2 we begin by considering the analysis of visibility-amplitude and closure-phase measurements, concentrating in particular upon the problem of model comparison. We develop a Bayesian framework for the problem, which we then use consistently throughout the remainder of the dissertation. • Chapter 3 is primarily concerned with the design and construction of the array and is therefore mainly a review. Also considered are the range of array configurations presenting available and the throughput of the optical beam-combination system. • Chapter 4 describes the practicalities of data acquisition at COAST and also discusses the estimation of visibility amplitudes and closure-phases from the raw data. The first angular diameter measurements from the array illustrate the quality of visibility amplitude data. • Chapter 5 is by far the most important in this work: the first true images from any separated-element optical array are presented. These represent the first proof that closure-phase imaging using a long-baseline optical interferometer is possible. • In Chapter 6 we consider observations of Betelgeuse which are important both technically and astrophysically. • Chapter 7 is concerned with observations of the Mira-type variable star R Leo. These revealed a pulsation-phase coherent variation in angular diameter at four wavelengths across two periods during 1996 and 1997.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available