21 Sep Discovering Mount Wilson Chapter 15: Hale Solar Laboratory
Image caption: Hale Solar Laboratory, as seen from the west-southwest, Pasadena. A small dome is set atop the roof of the tall portion of the building. A doorway and windows are seen in the side facing the camera. Trees grow around the building; an expansive dirt area is seen in the foreground. Credit: The Observatories of the Carnegie Institution for Science Collection at the Huntington Library, San Marino, CA.
Today we continue our ‘Discovering Mount Wilson’ series with chapter 15 about the Hale Solar Laboratory located in Pasadena. Once the personal office and observatory of Mount Wilson Observatory founder George Ellery Hale (1868-1938), it was used as his retirement getaway and for his continued research. This cultural and architectural icon was built in 1923 when Hale retired and, completed in 1925, and designated a National Historic Landmark in 1989.
The Hale Solar Laboratory is where Hale refined the spectrohelioscope, making it possible to perform detailed observations of the entire hydrogen atmosphere of the Sun. It is a complex machine that uses a spectroscope to scan the surface of the Sun. The image from the objective lens is focused on a narrow slit revealing only a thin portion of the Sun’s surface. The light is then passed through a prism or diffraction grating to spread the light into a spectrum. The spectrum is then focused on another slit that allows only a narrow part of the spectrum (the desired wavelength of light for viewing) to pass. The light is finally focused on an eyepiece so the surface of the Sun can be seen. The view, however, would be only a narrow strip of the Sun’s surface. The slits are moved in unison to scan across the whole surface of the Sun giving a full image.
Designed by the architectural firm of Johnson, Kaufman, and Coate, of Pasadena, The Hale Solar Laboratory was built in the shape of a “T.” There are six rooms in all, divided into two sections, the observatory and telescope, and the combined library and living room.
After Hale passed away in 1938, the Laboratory continued in use and was a valuable local space for Harold & Horace Babcock, for the development of the ‘magnetometer,’ which they later used to confirm the global magnetic field of the Sun. A distinctive blend of classic Spanish Colonial Revival and Mission Revival styles, The Hale Solar Laboratory is now privately owned and sits quietly in a Pasadena neighborhood.