A catalogue for the telescope computer is a set of user interface commands and as such can be in free format. For legibility and neatness, however, it is worth adhering to a more rigid tabular format with one object per line of the file. The guidelines for generating catalogues may be divided into essential rules (disregard of which will cause the interface to be unable to read in the file) and conventions (which are guidelines for producing catalogues which may be read in as quickly as possible and are easy to maintain).