SHS

(Spectrohelioscope)

The slit #2 is not in place. The bottom of the picture shows an inversion of the Ha-line due to a solar flare. This mode is called spectroscope. With slit #2 in place, one chooses how wide the selected line window, which syntezise the picture, can be.  This is a compromise between resolution and intensity (as with slit #1) in the final picture.