During COCO’s development, invaluable advice was received from the staff of Her Majesty’s Nautical Almanac Office at the Royal Greenwich Observatory, in particular Catherine Hohenkerk, Bernard Yallop and Brian Emerson. Thanks are also due to Noël Argue of Cambridge, to Andrew Lyne of Jodrell Bank, to Dick Manchester of CSIRO Radiophysics in Sydney for testing a pre-release version of COCO, to Mark Calabretta, also of Radiophysics, for supplying changes to allow COCO to be built for the Convex/ConvexOS platform, to Phil Hill (St. Andrews) for his advice on proper-motion handling, and to Leslie Morrison (RGO) for suggestions concerning parallax.