The Tycho Catalogue contains proper
motions and low precision parallaxes with a median
precisions of 25 mas, while having high precision
B and V magnitudes (median precision of 0.07 and
0.06 respectivly). The number of highparallax
stars is quite unexpected, with over 30 previously
unreferenced, non-Hipparcos, stars with a parallax
>500 mas and over 2000 with a parallax >250
mas. While many of these are probably mistakes,
the completeness limit of Tycho and the precise
magnitudes provide us with a way to intelligently
build a complete picture of the nearby star field.
Catalogues of nearby stars provide us with many
fundamental parameters in the field of stellar
astronomy, but the completness of known stars
within say even 8pcs is still underestimated by
about 30%, i.e., 50-60 systems (T.J. Henry, CSSS8,
ASP Conf Series 64, 1994).
In a new program at Torino we are using
the Tycho Catalogue to intelligently build a list
of possible candidates for a 1Opc volume. Figure 1
shows that Tycho will contain basically all ZAMS
to spectral type M3 within 10 pes, M5 to 4pcs and
M6 to 2pcs. A comparison of the photometric and
Tycho distances provides a list free of giants and
systems where binarity has affected the color.
This list is then added to the Torino Parallax
program where we expect to provide more precise
parallaxes.
Esiderata for nearby - star quantities observable with small telescope
