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The American astronomer George Ellery Hale used spectroscopic technology to build the spectroheliograph, a device that tracks the sun and photographically records an image of its perimeter, prominences, and corona. The above illustration depicts the way in which a spectroheliograph works. Light from a star enters the instrument at the bottom of this diagram from the right. The insert in the center of the diagram indicates the portion of the solar image that the instrument is selecting. The light then travels through a series of prisms, which break up and separate the different wavelengths. Finally, the light is passed through a slit at the top of the diagram. The slit may be moved so that the astronomer can study a particular wavelength of light. A photographic plate may be passed across this slit in order to record the wavelength of light selected for the star being studied. Not long after the development of the spectroheliograph, ruled gratings were developed. Ruled gratings bend light just like a prism, but they are more precise. |
