Selected Statistics from the Hipparcos and Tycho Catalogues

 

These images are extracted from Part 3 of Volume 1, and the ASCII CD-ROMs, where further details and additional plots are given.

 

 

The number of observed stars per square degree, in galactic coordinates. On the average there are 2.8 stars per square degree in the Hipparcos Catalogue.

 The median number of great-circle abscissae used for astrometry, in ecliptic coordinates. The median parallax, pi, in galactic coordinates. On the average the stars of the Hipparcos Catalogue are more distant in the galactic plane than outside this plane.

The median proper motion in right ascension in equatorial coordinates. The solar motion accounts for the preferentially positive proper motions at right ascension = 0 degrees and negative values at right ascension = 180 degrees.

The median proper motion in declination, in equatorial coordinates.

The median standard error of right ascension, in equatorial coordinates.

 

The median standard error of longitude, in ecliptic coordinates.

The median standard error of declination, in equatorial coordinates.

The median standard error of latitude, in ecliptic coordinates.

The median standard error of parallax, in equatorial coordinates.

The median standard error of parallax, in ecliptic coordinates.

The median relative precision of distance, sigma_pi/pi, for stars with a parallax pi >7.5 mas, in galactic coordinates.
The median standard error of proper motion in right ascension, in equatorial coordinates. The median standard error of proper motion in longitude, in ecliptic coordinates. The median standard error of proper motion in declination, in equatorial coordinates.
The median standard error of proper motion in latitude in ecliptic coordinates. The distribution is almost independent of the latitude for the same reasons as for the standard error of the ecliptic latitude. The remaining effect in longitude is due to the time distribution of the observations. The median correlation between right ascension and declination in equatorial coordinates. The systematic strucure is caused by the transformation from ecliptic to equatorial coordinates. The median correlation between longitude and latitude in ecliptic coordinates. Features are clearly connected to the scanning law.
The median duration between first and last observation, in ecliptic coordinates. The features are a direct consequence of the scanning law, the mission duration, and the observation interruptions. The median difference between mean observational epoch in right ascension and in declination, in ecliptic coordinates. The median colour index (B-V), in galactic coordinates. As expected most of the early-type stars are in the galactic plane while on the average those outside this plane are redder.
The median standard error in Hp magnitude, in galactic coordinates. The main structure is connected to the magnitude distribution. From the Tycho Catalogue: the number of observed stars per square degree, in galactic coordinates.

From the Tycho Catalogue: the median standard error of right ascension in ecliptic coordinates.
From the Tycho Catalogue: the median standard error of declination, in ecliptic coordinates.

From the Tycho Catalogue: the median standard error of proper motion in right ascension, in ecliptic coordinates.

 

 

From the Tycho Catalogue: the median standard error of proper motion in declination, in ecliptic coordinates.

From the Tycho Catalogue: the median colour index (B-V), in galactic coordinates.

Median difference between right ascension from the Tycho Catalogue and right ascension from the Hipparcos Catalogue, in equatorial coordinates. Median difference between declination from the Tycho Catalogue and declination from the Hipparcos Catalogue, in equatorial coordinates.
Median difference between right ascension from the Hipparcos Input Catalogue (after rotation to the Hipparcos reference frame) and right ascension from the Hipparcos Catalogue, in equatorial coordinates. Median difference between declination from the Hipparcos Input Catalogue (after rotation to the Hipparcos reference frame) and declination from the Hipparcos Catalogue, in equatorial coordinates. Median difference between proper motion in right ascension from the Hipparcos Input Catalogue (after rotation to the Hipparcos reference frame) and proper motion in right ascension from the Hipparcos Catalogue, in equatorial coordinates.
   
Median difference between proper motion in declination from the Hipparcos Input Catalogue (after rotation to the Hipparcos reference frame) and proper motion in declination from the Hipparcos Catalogue, in equatorial coordinates.