A CCD IMAGING SPECTROGRAPH IN THE IMPROVED SOLAR TOWER OF NANJING-UNIVERSITY

Since 1992 the solar tower telescope of Nanjing University (118 degree s 51' E, 32 degrees 03' N) as well as its multichannel solar spectrogr aph, originally established in 1982, have been reconstructed and a two -channel imaging spectrograph has been operated successfully. The aper tures of the coelostat and the secondary mirror are both 60 cm. The sp herical objective mirror, having an aperture of 43 cm and a focal leng th of 2170 cm, produces a solar image of 20 cm diameter. Two auxiliary telescopes using a small fraction of the coelostat's aperture were se t up for guiding and Hoc monochromatic monitoring. A multichannel spec trograph can be operated in six wavebands simultaneously. A CCD imagin g spectrograph can be used for data acquisition at H alpha and Ca Pi K line wavebands automatically and simultaneously. The instrument consi sts of two CCD cameras, an image processor (SR-151), a personal comput er, and a mechanical scanning device. The principal characteristics of the instruments are described. Some observational results are present ed as examples.