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Thesis (M.S.)--University of Wisconsin--Madison, 1970. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

An infra-red telescope, capable of detecting signals of the order of 10⁻⁶ watts incident on the mirror, has been built. RCA acorn type pentodes 954 and 956 have been examined as electrometer tubes in the region of grid current of 10⁻¹² amperes. It is indicated, on the basis of the small sample used, that the 954 is the better tube for this purpose. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "April 2007." Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph. D., Electrical Engineering)--University of Idaho, April 2007. / Major professor: David Egolf. Includes bibliographical references (leaves 156-161). Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (M.S.)--University of Kentucky, 2001. / Title from document title page. Document formatted into pages; contains x, 87 p. : ill. Includes abstract. Includes bibliographical references (p. 83-86).

Infrared astronomical observations have been severely limited by the radiation emitted by the aluminum coated surfaces of telescope mirrors. Hence, the reduction of emissivity with retention of coating durability for telescope optics is now an important area of study essential for the improvement of infrared astronomical observations. To avoid the considerable effort that a search for a new material superior to aluminum would demand with uncertain outcome, only existing materials were investigated and silver with a protective dielectric layer was thought to be a possible solution. Experiments at Kitt Peak National Observatory showed that the optical performance of a silver coating is better than aluminum in the infrared and visible regions, but even with a sapphire overcoating the silver proved to have such poor environmental resistence that an experimental mirror had to be recoated after just ten months in service. Thus, the improvement of the durability of a silver-based high reflectance coating becomes a key issue that has to be solved for such a coating to be selected for infrared astronomy. Furthermore, most telescopes are used also in the ultraviolet and so any successful coating would need to reflect well in this region. Silver is poor also in this respect. In this dissertation, we describe the development of a silver-based high reflectance coating that can withstand the humidity and pollution common in the open air and which has good ultraviolet, visible, and infrared performance. The successful design incorporates a silver reflective layer with a copper underlayer and a stack of dielectric overlayers. Prototypes of the candidate coating have been deposited on two-inch glass slides and tested in a controlled environmental chamber and under true operating conditions on Kitt Peak in Arizona. The improved durability, partly due to the copper underlayer, has been investigated with analytical techniques, including Rutherford backscattering. The results showed that the protection of the silver is due not only to the dielectric stack and the copper beneath the layer, but also to a small amount of copper that appears on the outer surface of the silver layer. This surface copper may result from diffusion through the silver layer after the coating deposition, or may be a consequence of a process during film growth. Whatever the reason, the candidate coatings have better optical performance and improved durability so they are recommended for use on large telescope mirrors for astronomical observations in the near ultraviolet, visible, and infrared spectral regions.

QC 351 A7 no. 30 / This symposium was co- sponsored by the Kitt Peak National Observatory (Dr. D. L. Crawford) and the Optical Sciences Center and Steward Observatory of the University of Arizona (Dr. A. B. Meinel). The idea grew from the recognition of the many common problems that were being faced by national and international groups in the engineering of large telescopes. The divergences of opinions and designs in regard to the nature of large astronomical mirrors, and their mounting and testing, made it evident that an exchange of ideas would be profitable to all of the groups. The meeting was organized and chaired by D. L.Crawford and A. B. Meinel. Special commendation is also due to R. H. Noble of the Optical Sciences Center for managing the numerous arrangements that contributed to making this a well-attended and successful symposium. The original intent of the symposium was merely to provide a face-to-face exchange of ideas. In retrospect, however, it was realized that the meeting constituted a milestone in large telescope design, and it was decided to edit the recording tapes and publish the proceedings. The task of transcribing the tapes fell to Patricia Grames and Evelyn Brant, with assistance in technical content from Earl Pearson of Kitt Peak National Observatory. In several cases the presentations atthe symposium led to continuing discussion. In particular,the papers by Bleich and Schwesinger led to a spirited exchange in which considerable enlightenment resulted. We have decided not to include these supplemental contributions, both because they transpired outside the format of this meeting and in view of their intent to publish elsewhere. The editorial task undertaken by Martha Stockton was immense and was impeded by prior responsibilities of all the persons involved. We are pleased to now conclude the report. We hope that readers will find this volume a useful addition to the limited available works on the topic of the design and testing of large astronomical telescopes. A. B. Meinel D. L. Crawford

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