Early star catalogues of the southern sky

Abstract

De Houtman in 1603, Kepler in 1627 and Halley in 1679 published the earliest modern catalogues of the southern sky. We provide machine-readable versions of these catalogues, make some comparisons between them, and briefly discuss their accuracy on the basis of comparison with data from the modern Hipparcos Catalogue. We also compare our results for De Houtman with those by Knobel in 1917 finding good overall agreement. About half of the ~ 200 new stars (with respect to Ptolemaios) added by De Houtman are in twelve new constellations, half in old constellations like Centaurus, Lupus and Argo. The right ascensions and declinations given by De Houtman have error distributions with widths of about 40′, the longitudes and latitudes given by Kepler have error distributions with widths of about 45′. Halley improves on this by more than an order of magnitude to widths of about 3′, and all entries in his catalogue can be identified. The measurement errors of Halley are due to a systematic deviation of his sextant (increasing with angle to 2′ at 60°) and random errors of 07. The position errors in the catalogue of Halley are dominated by the position errors in the reference stars, which he took from Brahe.