ASTRONOMICALOPTICSDanielJ.SchroederAstronomical OpticsDANIEL J.SCHROEDERDepartment of Physics and AstronomyBeloit CollegeBeloit,WisconsinACADEMIC PRESS,INC.Harcourt Brace Jovanovich,PublishersSan Diego New York BerkeleyBostonLondon Sydney Tokyo TorontoPhotograph on cover and Figure 17.2 courtesy of National Optical Astronomy Observato-ries.By accepting this product of the National Optical Astronomy Observatories (NOAO),the user agrees that the material may not be used to state or imply the endorsement byNOAO,or by any NOAO employee,of any individual,philosophy,commercial product,process,or service.COPYRIGHT 1987 BY ACADEMIC PRESS.INC.ALL RIGHTS RESERVED.NO PART OF THIS PUBLICATION MAY BE REPRODUCED ORTRANSMITTED IN ANY FORM OR BY ANY MEANS.ELECTRONICOR MECHANICAL.INCLUDING PHOTOCOPY.RECORDING.ORANY INFORMATION STORAGE AND RETRIEVAL SYSTEM.WITHOUTPERMISSION IN WRITING FROM THE PUBLISHER.ACADEMIC PRESS.INC.1250 Sixth Avenue,San Diego.California 92101United Kingdom Edition published byACADEMIC PRESS INC.(LONDON)LTD24-28 Oval Road,London NWI 7DXLibrary of Congress Cataloging in Publication DataSchroeder,D.J.Includes bibliographies and index.1.Astronomical instruments.2.Optics.I.Title.QB86.5351987681'.41287-1213ISBN 0-12-629805-X (alk.paper)PRINTED IN THE UNITED STATES OF AMERICA