an astronomical instrument designed to photograph the solar chromosphere in the central portion of some strong Fraunhofer line of the solar spectrum. The Hα line of hydrogen (653.6 nanometers) and the K line of ionized calcium (393.4 nanometers) are used most often for this purpose. In these spectral lines the chromosphere is opaque to radiation from the deeper layers of the sun.
A chromosphere telescope consists of a heliograph in which a monochromatic image of the sun is made with a special monochromator, usually an interference polarizing filter. The pass-band of the filter in the case of Hα should not exceed 0.05 nanometers, and generally is 0.02–0.01 nanometers. In order to make it possible to study chromospheric layers at various depths, the passband is shifted over the spectrum within the limits of the given spectral line. When it is tuned to the center of the line, the highest layers of the chromosphere are observed. The diameter of the image of the solar disk in the focal plane of the camera of a chromosphere telescope should be at least 2–3 cm for studying the chromosphere over the entire solar disk. In order to investigate the fine structure of individual details in the chromosphere, the diameter of the image is increased to 12–30 cm by means of special lenses. The chromosphere telescope is used in the Solar Survey to monitor solar flares and observe prominences. Cinematography is often used to record rapidly progressing chromospheric phenomena.
E. V. KONONOVICH