Country of Origin: United States of America
3-D Test: 114.3 x 61 x 94cm (45 x 24 x 37 in.)
3-D Test (Table): 114.3 x 76.2cm (45 x 30 in.)
Cast iron, anodized aluminum, optics, electrical components, light bulbs.
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.
Transferred from the U.S. Naval Observatory, Washington, DC