A spectrohelioscope is a type of solar telescope designed by George Ellery Hale in 1924 to be able to observe the Sun according to a determined wavelength of light. The name comes from three Latin words: Spectrum, referred to the spectrum of light; Helium, referred to the Sun; and Scopio, with the meaning of observing.
Description Typical scheme of a spectrohelioscope. The two grooves swiftly oscillate to pass successive portions of the sun's radiation (sweeping the solar disk) to be observed in monochromatic light. Many variations are possible: collimation can be done with concave mirrors, dispersion can be achieved with crystal prisms, and sweeping can be obtained with fixed slots and rotating square prisms. Since they are large (usually more than 3m long) and delicate apparatus, spectrohelioscopes usually remain fixed, being equipped with movable mirrors to follow the path of the sun.A basic spectrohelioscope is a complex machine that uses a spectroscope to analyze the surface of the Sun. The image formed by the lens is centered in a narrow slot, which passes only a thin portion of the Sun's surface. passes through a prism or diffraction grating to break it down into its spectrum. The spectrum is then centered in another slot, which only passes through a narrow part of the spectrum (with the wavelength to be observed). The light is finally centered on an eyepiece, where you can see the surface of the Sun. This image would be only a narrow strip of the surface of the Sun, were it not for the observation groove is endowed with a reciprocating movement that sweeps the entire surface of the Sun, obtaining a complete image of the solar disk. Regardless, oscillating mirrors can be used instead of slots to produce the same sweep effect: the first mirror selects one sector of the sun, and the second selects the desired wavelength.
The spectroheliograph is a similar device, but it captures photographically the images of the sun at a certain wavelength. At present it is still used in professional observatories.
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