Authors: Vieira Martins R., Veiga C. H., Bourget P., Andrei A. H., and Descamps P.
Year: 2004
Title: Systematic astrometric observations of Proteus
Journal: Astronomy and Astrophysics
Volume: 425
Pages: 1107-1111
Keywords: Neptune, small, observation, position, CCD, data
Abstract: Earth based observations of Proteus are made highly difficult by the magnitude difference with Neptune, and the closeness to the planet. To overcome these difficulties, observation campaigns using a Hg-mask coronograph developed for astrometry are being pursued at the Laboratò±¨¯ Nacional de Astrof첩ca, Brazil. The observations are made at visible light wavelengths with the 1.6 m reflector telescope. The large 4 arcmin Õ 4 arcmin field of view of the camera makes it possible to image a sufficient number of background stars that are used to carry out the astrometric analysis of these data. The first results of the campaigns are presented in this paper. They include 45 independent observations made over 2 nights in 2002. The positions are referred to the Hipparcos/Tycho2 frame. The mean offsets relative to the JPL ephemeris are -0.083 arcsec (sigma=0.148 arcsec) in the x=7Delta;alpha cos delta direction, and -0.051 arcsec (sigma=0.115 arcsec) in the y=Deltadelta direction. Additional astrometric data need to be collected in order to investigate further the possible offset of Proteus with respect to the Voyager ephemerides. For the sake of completeness the early 2000 and 2001 campaigns, although less accurate, are also discussed. The catalog is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/425/1107 Based on observations made at Laboratò±¨¯ Nacional de Astrof첩ca/MCT-Itajubíž¾í¼‚razil.
%F: AA(Observatò±¨¯ Nacional, Rua General Jos矃ristino 77, 20921-400 Rio de Janeiro, Brazil rvm@on.br; Observatò±¨¯ do Valongo, Ladeira Pedro Antó¨¯ 43, 20080-090 Rio de Janeiro, Brazil), AB(Observatò±¨¯ Nacional, Rua General Jos矃ristino 77, 20921-400 Rio de Janeiro, Brazil), AC(Observatò±¨¯ Nacional, Rua General Jos矃ristino 77, 20921-400 Rio de Janeiro, Brazil), AD(Observatò±¨¯ Nacional, Rua General Jos矃ristino 77, 20921-400 Rio de Janeiro, Brazil; Observatò±¨¯ do Valongo, Ladeira Pedro Antó¨¯ 43, 20080-090 Rio de Janeiro, Brazil), AE(Institut de M袡nique Cè«¥ste et de Calculs des È°h让rides, 77 avenue Denfert-Rochereau, 75014 Paris, France)
Bibliogaphic Code: 2004A%26A...425.1107V
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