Infrared Imaging Solar Spectrograph At Purple Mountain Observatory

Abstract

Since 1986, we have made some improvements to the multichannel solar spectrograph at Purple Mountain Observatory (PMO) step by step, and now we have developed and added to it a multichannel infrared imaging solar spectrograph. The original spectrograph can be used to observe simultaneously solar activity at 9 wave bands including Ca ii H and K line, Mg i b line, He i D3 line and Hα through H∞. The newly developed infrared imaging spectrograph can work in three wavelengths, i.e., He i 10830 Å, Ca ii 8542 Å, and Hα. We replaced plates in the original system with CCDs and placed an image reducer before each CCD in order to match the CCD pixel size. The dispersions for He i 10830 Å, Ca ii 8542 Å, and Hα of the new imaging solar spectrograph are 0.0693 Å, 0.0767 Å, and 0.0754 Å per CCD pixel respectively, and each vertical CCD pixel represents 0.34 arc sec of solar disk. We can obtain the line-center and off-band intensities of the three lines and the intensities of continua adjacent to these lines through the new instrument. We can also acquire velocity maps and line profiles. Therefore, it is specially suitable for two-dimensional (2D) spectroscopic observations of solar flares and active regions. We carry out scanning observation by rotating the second mirror of the coelostat system. In this paper, we introduce the improvements we made and the new imaging solar spectrograph. Some observation results are also presented in this article.