M2000: An astrometric catalog in the Bordeaux Carte du Ciel zone

Abstract

During four years, systematic observations have been conducted in drift scan mode with the Bordeaux automated meridian circle in the declination band +11\degr \leq \delta \leq +18\degr. The resulting astrometric catalog includes about $2.3\times 10^6$ stars down to the magnitude limit $V_{\rm M}=16.3$. Nearly all stars (96% ) have been observed at least 6 times, the catalog being complete down to $V_{\rm M}=15.4$. The median internal standard error in position is ${\sim} 35$ mas in the magnitude range $11 < V_{\rm M} < 15$, which degrades to ${\sim} 50$ mas when the faintest stars are considered. M2000 also provides one band photometry with a median internal standard error of ${\sim} 0.04$ mag. Comparisons with the Hipparcos and bright part of Tycho-2 catalogs have enabled us to estimate external errors in position to be lower than 40 mas. In this zone and at epoch 1998, the faint part of Tycho-2 is found to have an accuracy of 116 mas in α instead of 82 mas deduced from the model-based standard errors given in the catalog