The slit has a maximum length of 25.4mm (460 arcseconds) and a width which can be set from closure to a maximum of 25.0mm. The width of the slit projected on the detector can be calculated from the information given in Figure 2. At the f/7.5focus, 1 arcsecond corresponds to about 55 micron.
Figure 2: Anamorphic demagnification of the 1.5-meter Cassegrain spectrograph (solid line) as a function of the grating tilt angle. Also shown (dashed line) is the slit width which projects to 2 pixels on the detector.