Abstract
A new imaging system of the coronal green line (Fe XIV 5303 Å) was constructed at the Norikura Solar Observatory. The system consists of a 10-cm coronagraph, a tunable Lyot filter, and a cooled CCD camera. The transmission curve of the Lyot filter can be modulated by two liquid-crystal variable retarders. This scheme provides quick wavelength tuning and efficient subtraction of sky background. Two-dimensional distributions of the intensity and Doppler shift of the coronal green line can be obtained within 30 seconds with accuracies of better than 10−6I⊙ and 1 km s−1. Regular operation was started in 1997 September. The aim of the new system is to investigate plasma motions associated with the magnetic field reconnection and waves in the solar corona.
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