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Spectrograph, DTM Image Tube


Display Status:

This object is on display in the Explore the Universe exhibition at the National Air and Space Museum in Washington, DC.

Collection Item Summary:

Original Image Tube Spectrograph built in the early 1960s by W. Kent Ford, Jr., which he then used in collaboration with Vera Rubin to explore an observational problem she had developed: to determine the detailed rotational properties of galaxies. The cascaded image tube developed by Ford at the Carnegie and then manufactered by RCA improved quantum efficiency of photographic detectors by over a factor of ten and made it feasible to perform difficult observational programs like this. Analysis of observational data from this instrument led Rubin to the conclusion that there was a huge amount of unseen mass distributed throughout the visible matter in galaxies causing them to rotate like rigid bodies. This observation yielded evidence for the existence of dark matter that stimulated general acknowledgement that it forms a majority of the mass in the Universe. For her revolutionary work, Vera Rubin was the second woman in history to be awarded the Gold Medal of England's Royal Astronomical Society. The spectrograph was originally on loan to NASM from the Carnegie Institution of Washington and has now been accessioned into the collection as it represents the successful application of electronic amplification technology that led to a profound change in our understanding of the nature of the Universe.

Collection Item Long Description:

Data Source

National Air and Space Museum


Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum

Credit Line

Gift of Carnegie Institution of Washington, Department of Terrestrial Magnetism.


  • Metal case and structure
  • Glass optics
  • Electronics


  • 3-D: 73.7 x 35.6 x 106.7cm (29 x 14 x 42 in.)
  • Support: 72 × 37.5 × 34.5cm (28 3/8 in. × 14 3/4 in. × 13 9/16 in.)

Country of Origin

United States of America



Inventory Number