UofI_selenium_cell_photometer_mount_refractor_1910.jpg

Description selenium cell photometer mounted on a refractor, 1910, University of Illinois Observatory
Date
Source National Park Service
Author Dr. John Dickel
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( Reusing this file )
Public domain This image or media file contains material based on a work of a National Park Service employee, created as part of that person's official duties. As a work of the U.S. federal government , such work is in the public domain in the United States. See the NPS website and NPS copyright policy for more information.

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