The aims of the automatic control system are to position the mechanical axis of the telescope to specified right ascension and declination coordinates, and to track the right ascension axis smoothly at sidereal rate, atmospheric refraction variations being taken care of by an auto-guider. The design problems involved fall naturally into two groups, the mechanical ones of measuring the rotations of the axes and of applying drives to these, and the electronic ones of providing supervisory control and calculation facilities.

Solutions to these problems depend to a large extent on whether automatic control is being added to an existing telescope with existing drive systems, or a new telescope design is being carried out with automatic control in mind, and on whether an on-line process control computer is to be incorporated or not.