Visual observations of the solar atmosphere

Abstract

The spectrohelioscope, an instrument for observing the sun in monochromatic light, has been briefly described in a previous article. (1) The same optical parts employed in the preliminary work are now rigidly mounted in a vertical position in my new Solar Laboratory in Pasadena (a branch of the Mount Wilson Observatory). The second mirror of the coelostat, which stands at the summit of a low tower, sends the sun's rays vertically downward to a 30-cm. objective (kindly loaned me by the Yerkes Observatory) which forms a 5-cm. image of the sun on the slit of a spectroscope standing in a well excavated in the earth below the laboratory at the base of the tower.

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