Three acquisition and guider units are available, one dedicated to the
Wide Field Photographic Camera (WFC) at the f/8.06 focus, one dedicated
to CCD imaging at the f/15 Cassegrain focus, and one for use with
other instruments at the f/15 focus. In fact, only the first two incorporate
an autoguider. Guide stars can normally be found using the Guide Star
System, described in section 
.