Interior view of the snow telescope, showing the coelostat mirrors, Mount Wilson Observatory, ca.1930

Photograph of the interior view of the snow telescope, showing the coelostat mirrors, Mount Wilson Observatory, ca.1930. The tent-like opening at the eye of the horizontal telescope reveals the skies and the mountainous landscape. Exposed to externals, coelostat mirrors and contraptions to reposition it sits on a platform. A reflection of the land below is showing in the top mirror.; "The Snow Telescope, the oldest telescope on the mountain, is named after its benefactor, Helen Snow. She donated money for its construction at Yerkes Observatory in Williams Bay, Wisconsin. George Ellery Hale moved the telescope to Mount Wilson in 1904 to make observations of the Sun. Dr. Hale took the telescope on loan from Yerkes, although it has been here ever since. Unlike the two tower solar telescopes (which were built later), the light path for the Snow Telescope is horizontal. The building is long and originally was covered in canvas. This was a great fire hazard, and the crude building was replaced with an aluminum shell in 1911. Light from the Sun is reflected off the coelostat mirror (on the right partially in shadow) to another 30-inch mirror (at center) and reflected nearly horizontally 100 feet to the back of the building. There, it falls on a 24-inch concave mirror with a 60-foot focal length and is then brought to a focus at the entrance slit of the spectrograph as an image 6 1/2 inches across. The spectrograph is located in a 15-foot pit. Despite its simple construction, the horizontal light path of the Snow Telescope made observations difficult because heat from the sunlit ground affected the observational seeing. Therefore, shortly after being put into operation in 1904, plans were made to build the 60-foot Solar Tower." -- unknown author.