| Tycho2 catalogue |
| 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 (hereafter 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. Components of double stars with separations down to 0.8 arcsec are included. Proper motions precise to about 2.5 mas/yr are given as derived from a comparison with the Astrographic Catalogue and 143 other ground-based astrometric catalogues, all reduced to the Hipparcos celestial coordinate system. Tycho-2 supersedes in most applications Tycho-1, as well as the ACT and TRC catalogues based on Tycho-1. For more information, please consult the Tycho-2 home page. Required constraints:
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| Name | Type | Length | Unit | Description | Default Value | Unified Content Descriptor |
|---|---|---|---|---|---|---|
| id | varchar | 32 | Tycho2 identifier (constructed from the GSC region number) | meta.id;meta.main | ||
| hip | varchar | 16 | Hipparcos number | meta.id.cross | ||
| tyc1 | varchar | 8 | First part of Tycho2 identifier | meta.id.part;meta.main | ||
| tyc2 | varchar | 8 | Second part of Tycho2 identifier | meta.id.part;meta.main | ||
| tyc3 | varchar | 4 | Third part of Tycho2 identifier | meta.id.part;meta.main | ||
| id_tycho | bigint | 8 | Numerical Tycho2 identifier | meta.id;meta.dataset | ||
| tyc | varchar | 1 | Flag indicating Tycho1 stars | meta.code | ||
| ra | float | 8 | degrees | Observed Tycho2 Right Ascension in ICRS | meta.main;pos.eq.ra | |
| dec | float | 8 | degrees | Observed Tycho2 Declination in ICRS | meta.main;pos.eq.dec | |
| ra_deg | float | 8 | degrees | Observed Tycho2 Right Ascension in ICRS | pos.eq.ra | |
| de_deg | float | 8 | degrees | Observed Tycho2 Declination in ICRS | pos.eq.dec | |
| ra_m_deg | float | 8 | degrees | Mean Right Ascension, ICRS, epoch = J2000 | pos.eq.ra | |
| de_m_deg | float | 8 | degrees | Mean Declination, ICRS, epoch = J2000 | pos.eq.dec | |
| pm_ra | real | 4 | milliarcsec/year | Proper motion in RA*cos(Dec) | pos.eq.ra;pos.pm | |
| pm_de | real | 4 | milliarcsec/year | Proper motion in Dec | pos.eq.dec;pos.pm | |
| ep_ra1990 | real | 4 | years | Epoch - 1990 of ra_deg | time.epoch | |
| ep_de1990 | real | 4 | years | Epoch - 1990 of de_deg | time.epoch | |
| ep_ra_m | real | 4 | years | Mean epoch of ra (Julian years) | time.epoch | |
| ep_de_m | real | 4 | years | Mean epoch of dec (Julian years) | time.epoch | |
| num | smallint | 2 | NUmber of positions used | meta.number | ||
| e_ra_deg | float | 8 | milliarcsec | Standard error in RA*cos(Dec) of observed Tycho2 RA | stat.error | |
| e_de_deg | float | 8 | milliarcsec | Standard error of observed Tycho2 Dec | stat.error | |
| corr | float | 8 | Correlation (ra_deg,de_deg) | stat.correlation | ||
| e_ra_m_deg | float | 8 | milliarcsec | Standard error in RA*cos(Dec) of mean Tycho2 RA | stat.error | |
| e_de_m_deg | float | 8 | milliarcsec | Standard error of mean Tycho2 Dec | stat.error | |
| e_pm_ra | real | 4 | milliarcsec/year | Standard error in RA*cos(Dec) of RA proper motion | stat.error | |
| e_pm_de | real | 4 | milliarcsec/year | Standard error of Dec proper motion | stat.error | |
| q_ra_m_deg | real | 4 | Goodness of fit for mean RA | meat.code.qual | ||
| q_de_m_deg | real | 4 | Goodness of fit for mean Dec | meat.code.qual | ||
| q_pm_de | real | 4 | Goodness of fit for pm_de | meat.code.qual | ||
| q_pm_ra | real | 4 | Goodness of fit for pm_ra | meat.code.qual | ||
| pflag | varchar | 1 | Mean position flag | meta.code | ||
| posflg | varchar | 1 | Type of Tycho2 solution | meta.id;stat.fit | ||
| ccdm | varchar | 4 | CCDM component identifier for Hipparcos stars | meta.code.multip | ||
| prox | smallint | 2 | 0.1 arcsec | Proximity indicator | pos.angDistance | |
| bt_mag | real | 4 | mag | Tycho2 BT magnitude | phot.mag;em.opt.B | |
| vt_mag | real | 4 | mag | Tycho2 VT magnitude | phot.mag;em.opt.V | |
| e_bt_mag | real | 4 | mag | Standard error on BT | stat.error | |
| e_vt_mag | real | 4 | mag | Standard error on VT | stat.error | |
| cx | float | 8 | unit vector of spherical co-ordinates | pos.distance;pos.cartesian.x | ||
| cy | float | 8 | unit vector of spherical co-ordinates | pos.distance;pos.cartesian.y | ||
| cz | float | 8 | unit vector of spherical co-ordinates | pos.distance;pos.cartesian.z | ||
| htmID | bigint | 8 | Hierarchical Triangular Mesh (HTM) index, 20 deep, for equatorial co-ordinates | pos.eq | ||
| Total length | 271 |