The sun is a beautiful bright source of light. But how to use such an object, which is moving across the sky, to project something? For projection a beam of light has to have a fixed direction. In the 18th century, scientists such as ’s Gravesande and Fahrenheit had already devised a solution for this problem. The fixed beam of light was obtained by coupling a clock to a moving mirror in a smart way. This vastly improved, 19th century design of the German Klinkerfues was specially made for an accompanying spectrometer (cat. no. 607 / FK 0395). Both instruments were acquired by the conservator Van der Willigen, presumably for the new observatory then being built in the museum garden.
Heliostat, after Klinkerfues
1865