binocular microscope "star counting" machine
Date: circa 1930
Inventory Number: 2005-1-0016
Classification: Star Counting Machine
Subject:
Maker: Spencer Lens Company (1895 - 1945)
Maker: Harvard College Observatory (founded 1839)
User: Bartholomeus Jan Bok (1906 - 1983)
Cultural Region:
Dimensions:
55 x 90 x 43 cm (21 5/8 x 35 7/16 x 16 15/16 in.)
Description:
A Greenough-type stereoscopic microscope by Spencer Lens Company is attached to an articulated arm, which permits it to travel across an iron frame. The frame is adjustable in height by means of a chain and pulley with counter weights. The frame is translated in a horizontal fashion by means of a coarse gear . The frame would have held a photographic plate of a star field. A rectangular piece of milky glass is behind the frame and comes between it and a light bulb. The stand is of cast iron.
Signedon binocular microscope's prism housing: SPENCER / BUFFALO / U.S.A. [in trademark]
Inscribedon prism housing: 124092
FunctionThe "star counting" machine was an instrument for examining photographic plates of star fields with a stereoscopic microscope. It was used for estimating the magnitudes of stars, counting them, and studying variable stars.
Estimates of magnitude were made by the fly-spanker method. A series of spots of increasing size were arranged on a piece of film. The strip was held beside the image of the star to be measured on the photographic plate. The observer estimated which of the spots was nearest in size to the star. By comparison with known standards, it was possible to calibrate the spots in magnitudes. The term "fly-spanker" referred to similarity between the strip and a fly swatter.
Estimates of magnitude were made by the fly-spanker method. A series of spots of increasing size were arranged on a piece of film. The strip was held beside the image of the star to be measured on the photographic plate. The observer estimated which of the spots was nearest in size to the star. By comparison with known standards, it was possible to calibrate the spots in magnitudes. The term "fly-spanker" referred to similarity between the strip and a fly swatter.
Historical AttributesThis "star counting" machine was built and used at the Harvard College Observatory for measuring the magnitudes of stars in the 1930s.
Harvard sent others just like this one to six different observatories around the world who were taking part in the Fourth Harvard Star Count Circuit in the 1930s.
Bart Bok describes the project in The Milky Way (one of the Harvard Books on Astronomy).
A photograph of the astronomer, Bart Bok doing research in 1933 on a star counting machine at the Harvard College Observatory is attached to this file. Another photograph shows the Observatory director, Harlow Shapley, sitting at an instrument that Harvard sent to the Armagh Observatory around 1937 when he visited the Armagh Observatory in the 1950s.
Harvard sent others just like this one to six different observatories around the world who were taking part in the Fourth Harvard Star Count Circuit in the 1930s.
Bart Bok describes the project in The Milky Way (one of the Harvard Books on Astronomy).
A photograph of the astronomer, Bart Bok doing research in 1933 on a star counting machine at the Harvard College Observatory is attached to this file. Another photograph shows the Observatory director, Harlow Shapley, sitting at an instrument that Harvard sent to the Armagh Observatory around 1937 when he visited the Armagh Observatory in the 1950s.
ProvenanceHarvard College Observatory.