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Microscope, Astronomical, Stereo Blink.


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:

This is a blink stereo comparator microscope manufactured about 1960 by the C. Ridell Company of Williams Bay, Wisconsin for the U. S. Naval Observatory. It is typical of a class of discovery devices used in photographic astronomy from the late 19th through the 20th centuries to detect variable stars and asteroids, and high-proper motion stars. Two photographs of the same part of the sky were placed side by side in parallel microscopes that through a set of mirrors combined the two images, allowing the observer to switch rapidly between the two aligned scenes. Anything in the field of view that changes becomes visible through a shifting or pulsating image. In this design, the usual viewing eyepiece has been replaced with a system that projects images of the plates onto a circular screen. This reduced the fatigue of this tedious operation, which sometimes could take decades. It was transferred to NASM by the U S Naval Observatory in 1996 and is now on display in the Explore the Universe gallery utilizing modern low-voltage halogen illumination to demonstrate the technique.

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

Transferred from the U.S. Naval Observatory, Washington, DC


Cast iron, anodized aluminum, optics, electrical components, light bulbs.


  • 3-D: 114.3 x 61 x 94cm (45 x 24 x 37 in.)
  • 3-D (Table): 114.3 x 76.2cm (45 x 30 in.)

Country of Origin

United States of America


EQUIPMENT-Scientific Devices

Inventory Number