One of 41 bromide photographic prints related to and showing various stages in the construction of the Hooker 100 inch reflecting telescope at Mount Wilson, California showing the top section of the main girder of the dome being raised into its final position from the moving balcony floor. The observatory was founded in 1904 by the astronomer George Ellery Hale (1868-1938). The 100 inch reflecting telescope installed at the observatory in 1917 was the largest telescope in the world at the time, and remained so until the 200 inch reflector at Mount Palomar became operational in 1948. Mount Wilson was at the forefront of astronomy in the first half of the 20th century. Observations by astronomers working there confirmed that the Universe was expanding, as well as leading to substantial advances in understanding of the workings of the Sun.
© Science Museum / Science & Society Picture Library