Materials from the Caltech Archives are made available online for research purposes. Permission for reproduction, distribution, public display, performance, or publication must be obtained in writing from the Head of Archives. The Caltech Archives makes no representation that it is the copyright owner in all of its holdings. It is the responsibility of the user to obtain all necessary rights and clearances for use of materials. For questions, contact Head of Archives.
Perspective drawing of oscillating slits and eyepiece of spectrohelioscope. Pencil and ink on paper, backed with graph paper, 8.5 x 11 inches, signed R. W. P., dated 1929. George E. Hale, "The Spectrohelioscope and its Work, Part I: History, Instruments, Adjustments, and Methods of Observation, The Astrophysical Journal 70 (December 1929): 265-311. Published as Plate IX. Porter Papers. 1929