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Mount Wilson Observatory Optical Shop Papers: Finding Aid
mssMount Wilson optical shop  
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Collection Details
Table of contents What's This?
  • Overview of the Collection
  • Access
  • Administrative Information
  • Historical Note
  • Scope and Content
  • Arrangement
  • Indexing: Added Entries
  • Indexing Terms

  • Overview of the Collection

    Title: Mount Wilson Observatory Optical Shop Papers
    Dates (inclusive): 1911-1966
    Bulk dates: 1930-1947
    Collection Number: mssMount Wilson optical shop
    Creator: Mount Wilson Observatory Optical Shop.
    Extent: 931 items in 8 boxes
    Repository: The Huntington Library, Art Collections, and Botanical Gardens. Manuscripts Department
    1151 Oxford Road
    San Marino, California 91108
    Phone: (626) 405-2129
    Email: reference@huntington.org
    URL: http://www.huntington.org
    Abstract: This collection contains records of the Mount Wilson Observatory Optical Shop, relating to the operation of the department from 1911 to 1963 (bulk 1930-1947). The department was responsible for repairing and maintaining the Observatory's telescopes, as well as for observatories around the United States. The materials include research and procedural notes, correspondence, inventories and requisition slips, and job lists and employee time sheets.
    Language: English.


    Open to qualified researchers by prior application through the Reader Services Department. For more information, contact Reader Services.

    Administrative Information

    Publication Rights

    The Huntington Library does not require that researchers request permission to quote from or publish images of this material, nor does it charge fees for such activities. The responsibility for identifying the copyright holder, if there is one, and obtaining necessary permissions rests with the researcher.

    Preferred Citation

    [Identification of item]. Mount Wilson Observatory Optical Shop Papers, The Huntington Library, San Marino, California.


    Deposit, Observatories of the Carnegie Institution of Washington Collection, 1988. Approximately fifty additional separate collections form the Mount Wilson Papers of the Observatories of the Carnegie Institution of Washington and are available for research in the Manuscripts Department of the Huntington Library.

    Historical Note

    Founded in December 1904 by George Ellery Hale and funded by the Carnegie Institution, the Mount Wilson Observatory quickly became one of the 20th century’s major astronomical research centers. Located just north of Los Angeles high atop the San Gabriel Mountains, the observatory took full advantage of Southern California’s clear nights and uniquely steady air. The observatory’s 60’’ telescope completed in 1908 was the largest then in existence. In 1917, another Mount Wilson telescope, 100’’ in diameter, claimed that title. The Optical Shop was the department responsible for repairing and maintaining these telescopes. Optical Shop workers ground and polished mirrors, lenses, and prisms: tasks requiring meticulous precision and technique. In addition to serving Mount Wilson, the Optical Shop produced optical instruments for observatories across the country.
    During the Second World War, the Mount Wilson Observatory Optical Shop played an important role in U.S. war effort. Shop technicians produced roof prisms for military optics on a large scale, eventually publishing an instruction manual for other optical workshops. Experiments with newly-invented Schmidt cameras helped develop the field of aerial photography. New camera shutters and film sweep mechanisms were invented. Procedures for measuring lens resolution were tested.

    Scope and Content

    The Mount Wilson Observatory Optical Shop Papers comprise 8 boxes of material relating to the operation of the department from 1911 to 1963 (bulk 1930-1947). This material is divided into four general categories: research and procedural notes, correspondence, inventories and requisition slips, and job lists and employee time sheets. Each group is arranged chronologically. Various scientific manuals, brochures, and unidentified notes have been gathered into a folder of ephemera.
    Shop notebooks form the bulk of the research material. These notebooks outline various procedures for grinding and polishing mirrors, drilling glass, and configuring lenses. Several notebooks track the construction of the observatory’s 100’’ Hooker telescope as well as the 200’’ Hale telescope housed at the California Institute of Technology’s Palomar Observatory. Declassified research on aerial photography for the National Defense Research Committee is included in several progress reports.
    The majority of correspondence is between Optical Shop technicians and astronomers both at Mount Wilson and elsewhere around the country. These letters are generally technical in nature with the various interlocutors trying to solve specific optical problems. Several manufacturing firms solicit the Optical Shop personnel about their products. Walter S. Adams and Don O. Hendrix participate in the bulk of the correspondence. Included is Hendrix’s signed “Pledge of Secrecy” and commission from the Office of Scientific Research and Development. Inventory notebooks detail the supplies used in the Optical Shop: everything from towels and paper goods to slabs of optical glass and chemical solvents. Lists of lenses, mirrors, and prisms record material in stock and material lent out to other institutions. Requisition slips and shipping invoices illustrate the broad network of suppliers the shop needed for their highly specialized work.
    A number of notebooks chart the myriad jobs the Optical Shop performed for both the Mount Wilson Observatory and other institutions. These notebooks assign each job a number, outline the work, and list the employees working on it. Separate employee time charts are also included with address and contact information for each.
    Notable participants include: Walter S. Adams, who succeeded Hale as director of the observatory, Don O. Hendrix, the Shop's chief optician and Ira Sprague Bowen, Bannevar Bush, Robert E. Hopkins, Brian O'Brien, Frank E. Ross, and Jet Propulsion Laboratory.
    Note: Two inventory notebooks have been treated for mold and are held separate from the main collection. Please contact Reader Services for access to these notebooks.


    Arranged in 8 boxes in the following order:
    • Boxes 1-2: Research and Procedure Notes
    • Box 3: Correspondence
    • Boxes 4-6: Shop Inventories, Invoices, and Requisition Slips
    • Boxes 7-8: Job Lists and Time Charts and Ephemera

    Indexing: Added Entries

    Adams, Walter S. (Walter Sydney), 1876-1956.
    • Addressee of Frank E. (Frank Elmore) Ross, 1874-1960 letter (1936, May 30). Box 3 (1).
    • Addressee of B.H. Witherspoon letters (1941, July-1941, Aug.). Box 3 (5). Addressee of Benjamin Liebowitz letter (1945, Dec. 10). Box 3 (29).
    Bowen, Ira Sprague, 1898-1973.
    • Addressee of Jet Propulsion Laboratory (U.S.) letter (1949, Nov. 22). Box 3 (40).

    Indexing Terms

    The following terms have been used to index the description of this collection in the Huntington Library's Online Catalog.  


    Carnegie Institution of Washington.
    Mount Wilson and Palomar Observatories.
    Mount Wilson Observatory -- History -- Sources.
    Mount Wilson Observatory Optical Shop.
    Office of Scientific Research and Development.
    Astronomers -- United States -- Correspondence.
    Astronomical observatories -- California -- Wilson, Mount (Mountain)
    Astronomical photography -- Equipment and supplies.
    Astronomy -- United States -- History -- 20th century -- Sources.
    Astrophysics -- History -- 20th century -- Sources.
    Telescopes -- Design and construction -- History -- Sources.


    Inventories -- California -- 20th century.
    Letters (correspondence) -- United States -- 20th century.
    Notebooks -- California -- 20th century.
    Time sheets -- California -- 20th century.

    Additional Contributors

    Adams, Walter S. (Walter Sydney), 1876-1956.
    Bowen, Ira Sprague, 1898-1973, recipient.
    Bush, Vannevar, 1890-1974.
    Hendrix, Don O.
    Hopkins, Robert E. (Robert Earl)
    O'Brien, Brian, 1898-1992.
    Ross, Frank E. (Frank Elmore), 1874-1960.
    Jet Propulsion Laboratory (U.S.)
    Mount Wilson Observatory.