The Astrophysical Observatory of the California Institute of Technology

Abstract

Introduction. - Gift by Rockefeller Trustees to California Institute of Technology of fund to establish and Astrophysical Observatory with 200-inch telescope; co-operation with Carnegie Institution of Washington. The 200-inch telescope. - Selection of equatorial reflector; mirror disks; experiments with fused silica; adoption of new type of Pyrex glass, of low-temperature expansion; successful production of 60-inch, 120-inch, and 200-inch Pyrex disks; development of aluminum mirror surfaces; types of equatorial mountings; yoke type selected. Site. - Choice between Northern and Southern hemispheres; mountain site near California Institute and Mount Wilson Observatory necessary for most effective work; five years' study of meteorological, topographical, and astronomical conditions at several favorable sites; other requirements; final selection to be made soon. Astrophysical laboratory. - Purposes of laboratory; site in Pasadena on California Institute campus; brief description. Instrument shop. - Purpose; site; equipment. Optical shop. - Requirements; site; equipment. Auxiliary instruments. - Attachments of 200-inch telescope; Ross correcting lens; tests with Mount Wilson telescopes; Rayton spectrograph lens; spectra of remote spiral nebulae photographed with 100-inch telescope; extremely short-focus lens designed by British Scientific Instrument Research Association; development of photographic amplifier by Stebbins and Whitford; use with 100-inch telescope; radiometers, etc.