Natural Satellites Service. Special ephemerides
Apparent Encounters
of the Tycho-2 Catalogue stars and the main natural planetary satellites
by S.Vashkovyak
Suggestions
- The Tycho-2 star catalogue is recently used as a realization
of astrometric observations. The Tycho-2 Catalogue is
an astrometric reference catalogue containing positions
and proper motions as well as two-colour photometric data
for the 2.5 million brightest stars in the sky. The Tycho-2
positions and magnitudes are based on precisely
the same observations as the original Tycho Catalogue
(Tycho-1) collected by the star mapper
of the ESA Hipparcos satellite, but Tycho-2 is much bigger
and slightly more precise owing to a more advanced
reduction technique.
- Of particular interest are the cases
when the Galilean satellites of Jupiter
or the major Saturnian satellites and the stars from this
catalogue appear on the same CCD frame field.
If a satellite is observed at a distance not exceeding several
arcminutes from a star, it is possible to receive
high-precision CCD-observations of this satellite which, when averaged,
should ensure construction of a normal place with the
accuracy of as much as few thousandths arcseconds.
Assuming that the relative positions
of the Galilean satellites given by the Lieske's theory
and those of the main satellites of Saturn (S1-S8) given by the theory
of Harper and Taylor are exactly correct,
normal places for the positions of Jupiter or Saturn
at the mean epoch of the observations are constructed.
- Here we present the precalculated circumstances
of the apparent encounters of the stars of the Tycho-2 Catalogue
with the main satellites of Saturn (S1-S8)
for the period from November 2004 to February 2010,
and with the Galilean satellites of Jupiter for the period from
November 2004 to October 2010.
- The assumptions:
The differences of the stellar magnutudes of the “star-satellite” pair should be
no more than 3 vmg. The
apparent angular distances between the star and the satellite should not exceed 6 arcminutes
for the main Saturnian satellites (S1-S8) and 15 arcminutes for the Galilean satellites of Jupiter.
- Instead of three numbers (ntch1 ntch2 ntch3) describing
a position of a star in the Tycho-2 catalogue,
the conditional number is given. The conformity is presented in a
tabular form in the beginning of the ephemerides.
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Acknowledgements:
This work was supported by the Russian Foundation for Basic
Research, project no. 03-02-17441.
Celestial mechanics department / Sternberg Astronomical Institute /
Moscow University
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