CPC2: the second cape photographic catalogue. I: History, observations and plate measurements

The observational programmes carried out during the past forty years, for constructing the stellar reference frame in both hemispheres are reviewed briefly; a major contribution is the Second Cape Photographic Catalogue (CPC2) containing positions and visual magnitudes for 276 131 stars covering the whole southern hemisphere, at mean epoch 1968. A total number of 5280 plates with a complete fourfold overlap pattern were taken at the Royal Observatory, Cape of Good Hope, with a specially designed astrometric camera. All plates were measured on the GALAXY automatic measuring machine at the Royal Greenwich Observatory, and plate reductions have been carried out at Hamburger Sternwarte. The accuracy of a catalogue position is about 60 mas in each coordinate and preliminary proper motions are given for 124 000 stars