C2A is able to read a compiled version of the UCAC1 catalogue (First U.S. Naval Observatory CCD Astrograph Catalogue). The UCAC1 catalogue, published by the US Naval Observatory, is a high precision high density astrometric catalogue which references around 27 million stars between magnitude 8 and 16 in the Southern hemisphere. It is the first stage in a project to cover the whole sky. The catalogue gives positions, proper motions, errors in position and proper motion, as well as approximate magnitudes. You select the UCAC1 catalogue as the current catalogue through the Stars tab of the Options dialogue box, or by SHIFT-right-clicking on the map.
C2A takes into account the proper motions given in the UCAC1 catalogue in determining star positions at a date specified by the user.
If you have the original UCAC1 catalogue, the Tools page of the C2A Website provides a tool for compiling it in the C2A format. All the information needed to compile the catalogue is given on that page.