Showing papers by "Julio Camargo published in 2001"

Investigation of USNO-A2.0 Catalog Positions

Abstract: We present an investigation of the USNO-A2.0 Catalog positions. We have compared USNO-A2.0 positions with the Astrographic Catalogue-Tycho, with improved HST Guide Star Catalog positions in the ACT frame, and with International Celestial Reference Frame source positions and observational data from Valinhos CCD Meridian Circle, covering all the USNO-A2.0 magnitude range within 7 ≤ V ≤ 22. We report striking, peculiar features first found for the USNO-A2.0 catalog positions, which are different for its northern and southern parts.

Extension of the ICRF for selected areas down to the 16th magnitude – II

Abstract: In this paper we provide a major upgrade of the work presented in Camargo et al. (2001), aiming at the extension of the ICRF at optical wavelengths in regions of special astronomical interest, using observations from the Bordeaux and Valinhos meridian circles. Along with the new fields, the main differences, when compared to the first release, are: a much larger sky coverage, the replacement of the AC2000 by its upgraded version AC2000.2 as one of the first epoch astrometrical sources, inclusion of Tycho-2 and 2MASS photometry when available, and the correction for a magnitude equation on the Valinhos right ascension system as well. The resulting catalogue contains 678 828 entries with positional external precisions, on both coordinates, ranging from 50-60 mas (V ≤ 13.5) to 70-140 mas (13.5 < V ≤ 16.0). For the proper motions, precisions range from 3 mas/year to about 15 mas/year, depending on magnitude and declination.