DESIGN ASPECTS OF FUTURE VERY LARGE TELESCOPES (HONEYCOMB MIRRORS). Item Type text; Dissertation-Reproduction (electronic) Authors Cheng, Andrew Yuk Sun Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 06/10/2021 07:16:31 Link to Item http://hdl.handle.net/10150/183998 INFORMATION TO USERS While the most advanced technology has been used to photograph and reproduce this manuscript, the quality of the reproduction is heavily dependent upon the quality of the material submitted. For example: • Manuscript pages may have indistinct print. In such cases, the best available copy has been filmed. • Manuscripts may not always be complete. 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For an additional charge, 35mm slides of 6"x 9" black and white photographic prints are available for any photographs or illustrations that cannot be reproduced satisfactorily by xerography. 8709888 Cheng, And rew Yuk Sun DESIGN ASPECTS OF FUTURE VERY LARGE TELESCOPES The University of Arizona PH.D. 1987 University Microfilms International 300 N. Zeeb Road, Ann Arbor, MI48106 PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark~. 1. Glossy photographs or pages __ 2. Colored illustrations, paper or print ___ 3. Photographs with dark background __ 4. Illustrations are poor copy ___ 5. Pages with black marks, not original copy ___ 6. Print shows through as there is t~xt on both sides of page ___ 7. Indistinct, broken or small print on several pages /' 8. Print exceeds margin requirements ___ 9. Tightly bound copy with print lost in spine ___ 10. Computer printout pages with indistinct print ___ 11. Page(s) lacking when material received, and not available from school or author. 12. Page(s) seem to be missing in numbering only as text follows. 13. Two pages numbered . Text follows. 14. Curling and wrinkled pages ___ 15. Dissertation contains pages with print at a slant, filmed as received ____ University Microfilms International DESIGN ASPECTS OF FUTURE VERY LARGE TELESCOPES by Andrew Yuk Sun Cheng A Dissertation Submitted to the Faculty of the DEPARTMENT OF ASTRONOMY In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 1987 STATEMENT BY AUTHOR This dis13ertation has been submitted in partial fulfillment of require­ ments for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special per­ mission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the ma­ terial is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: __~~~ __ ~_~ __ THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Final Examination Committee, we certify that we have read the dissertation prepared by Andrew Yuk Sun Cheng entitled _____D~e~s~i~g~n~A~s~p~e~c~t~s~o~f~F~u~t~u~r~e~V~e~r~y~. ~L_a_r~g~e__ T_e~l~e~s~c_o~p~e~s __________________ and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy I /L./ YI Date 7 ' r I~( 8=r- Date 1/ '- / 'i:t Date )/£ f <;(7 Date {, (~( &-2 Date Final approval and acceptance of this dissertation is contingent upon the candidate's s';ubnission of the final copy of the dissertation to the Graduate College. I hereby certify that I read this dissertation prepared under my direction and recommend it be accepted as fulfilling the dissertation ent. .,)1 I /~I It7 Date I I DEDICATION To my wife Yuk Chu. iii ACKNOWLEDGEMENTS The author wishes to thank his dissertation advisor, Dr. J. Roger P. Angel, for his support, guidance and suggestions, and his many enlightening dis­ cussions. He also wants to thank Dr. Nick J. Woolf for suggesting the topic of large ielescope design and discussing many aspects and problems in this disser­ tation. He also wants to thank Drs. E ..Keith Hege, Peter A. Strittmatter and William F. Hoffmann for their help in completion of this dissertation. The author wants to thank D. Blanco, L. Goble, K. Johnson, D. Mitchell, C. Poland, S. Schallar and D. Young for the many engineering ideas he learned during the meetings and discussions of the stressed lap project. Special thanks to David S. Brown and Bob Parks for their helpfur discussions and suggestions on polishing technology. The author wants to thank D. Watson, S. Kopke, P. Wangsness, K. Kenagy, K. Johnson and J. Evans for their help in the thermal ventilation experiment. Many thanks to Dr. Buddy Martin for an intensive read­ ing of this dissertation and for his critics and suggestions. Tile autllor wants to thank Drs. VI. J. Cocke, J. R. Jckipii, H. P. Larson, J. W. Liebert, A. G. Pacholczyk, G. H. Rieke, T. L. Swihart, P. A. Strittmatter, R. I. Thompson, W. G. Tifft, R. J. Weymann and R. E. Williams for their teachings in astronomy and astrophysics. He also wants to express gratitude to Drs. E. K. iv v Hege, A. G. Pacholczyk, P. A. Strittmatter, W. G. Tifft and N. J. Woolffor serving as members of his preliminary examination committee. He wants to express special thanks to Drs. J. M. Beckers, W. J. Cocke, J. Drummond, E. K. Hege, P. A. Strittmatter and N. J. Woolffor their teachings in speckle interferometry research. He would like to thank all of his fellow graduate students for creating a friendly and helpful learning environment. The author wants to acknowledge research supports from Drs. J. R. P. Angel and E. K. Hege, and teaching and research assistantship from the depart­ ment of astronomy. He would also like to thank the Steward Observatory scientific, technical and secretaria.l staff for their many helps during these years as a graduate student. Finally, he wants to specially thank his wife Yuk Chu for her support, understanding and caring during his career as an astronomy graduate student. He also wants to thank her for help in typing the manuscript. TABLE OF CONTENTS Page . LIST OF ILLUSTRATIONS .x LIST OF TABLES . xii ABSTRACT .... xiii 1. INTRODUCTION . 1 2. MOTIVATIONS FOR VERY LARGE TELESCOPES . 6 Introduction • • . • • . .. 6 A Very Large Telescope • • • • • . • • . • • • • 6 Scientific Importance of a Very Large Telescope . 11 Galaxies and Clusters of Galaxies . • 11 Quasars and Active Galactic Nuclei • 12 Star Formation . • . 14 Structure of Late Type Stars . ..... 14 Planetary Studies • . 14 Capability Requirements . ... • 15 Important Design Aspects . • . 15 3. POLISHING LARGE FAST ASPHERICS • • 19 Intrudu.ction • . • • . • . • 19 Why Large f/1 Mirrors are Difficult to Polish .. 19 Different Methods of Mirror Polishing . 24 The Classic Method of Polishing . 24 Full Size Lap Approach . • . 31 Sub-Diameter Lap Approach (Zonal Figuring) 33 Computer Assisted Polishing . • . • • • 35 Computer Controlled Polishing • . 37 Bent Mirror Polishing . • . 39 Pressure Bending of the Mirror . 40 Stress Bending of the Mirror . 41 vi vii TABLE OF CONTENTS - Continued Page Bent Lap. Polishing . • . 43 Gravitational Bending of a Full Size Lap . 43 Stress Bending of a Sub-Diameter Lap . • 44 The Best Method of Polishing 8m f/1 Mirrors 45 4. DESIGN STUDY OF A SUB-DIAMETER STRESSED LAP 41 Introduction . • . • . • . 41 Overview of a 0.6m Stressed Polishing Lap . 48 Needed De:8.ection of the Lap • . • . 53 Exact Form of an Off-Axis Paraboloid . 54 Approximate Form of an Off-Axis Paraboloid. • . 51 The Intrinsic Shape of the Lap • . • . 59 Approximate Form of the Needed De:8.ection • . 62 Alternate Approximation of the Needed De:8.ection 63 Measured Influence Function • . 65 The 24 Actuator Forces ••... 69 Actuator Cable Design .••.. 11 Other Needed Engineering Details . 84 5. COMPUTER CONTROLLED STRESSED LAP POLISHING 85 Introduction . • . • 85 Control Accuracy of Stressed Lap • . • . 85 Error Budget . • . • . • 86 The Resolution for the Lap Position Angle . 92 The Resolution for the Lap Radial Position 92 Lap Metrology Accuracy • . • . 92 Requirements on the Stressed Lap Control Computer 93 Computer Update Frequency . • ..•. 93 Cc"'"puter Speed . .. .. .. .. .. .. 0 ~ 0 0 0 93 Computer Memory • • • • . • 93 Stressed Lap on a Strasbaugh Polishing Machine 94 The Strasbaugh Polishing Machine . • • . 95 The Machine Kinematics. • . • . 91 Machine Modifications for Stressed Lap Polishing 99 Computer Controlled Stressed Lap Polishing Machine • . 104 viii TABLE OF CONTENTS _. Continued Page Computer Assisted Stressed Lap Polishing . • . ... 106 Automated Computer Controlled Stressed Lap Polishing .