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The Snow Solar Telescope

The Snow Solar Telescope alongside the 60-ft Tower.

The Snow Telescope, the oldest telescope on the mountain, is named after the father of 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. Unlike the two tower solar telescopes that were built later, the light path for the Snow Telescope is horizontal. The building is long and originally was covered in canvas to keep the Sun from heating the ground along the light path of the telescope. This was a fire hazard and the crude building was replaced with an aluminum shell in 1911.

Setting the telescope
Observers on the coelostat platform of the telescope.

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 that brings the light to a focus at the entrance slit of the spectrograph as an image of the Sun 6 1/2 inches across. The spectrograph is located in a 15-foot pit. Many important observations were made with the Snow telescope and its instruments but tests soon indicated that a vertical construction would avoid some of the problems associated with heat from the sunlit ground near the mirrors. Shortly after going into operation in 1904, therefore, plans were begun for build the 60-foot Solar Tower. .