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The formerly spectrohelioscope, that was used to observe the Sun in Hα light until
the early 70ies, was coverted into a small spectrograph. The spectrohelioscope was in use
until a new Lyot filter was bought.
The spectrograph can be illuminated by Sun light, that is deflected by a small heliostat mounted on the
outside of the obervation tower (right image), or by specail lamps (Helium, Hα, Sodium). The observed
wavelength can be set via crank and covers the full visible light range. For faster wavelength
shifting the crank is coupled with a motor.
The spectrograph is not used for solar observations, as its resolution is not sufficient.
It is mainly used to measure the wavelength and bandwidth of filters before they are
used in a solar telescope. The lower left image shows the determination of the FWHM and the wavelength of
a DayStar Hα filter. The spectrum can be view directly with an eyepiece or by
turning a mirror the light is deflected to a camera.
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