The database is a subset of the data in three major catalogs: the Hipparcos Catalog,the Yale Bright Star Catalog (5th Edition), and the Gliese Catalog of Nearby Stars (3rd Edition). Each of these catalogs contains information useful to amateur astronomers:
The name of the database comes from the three catalogs comprising its data: Hipparcos, Yale, and Gliese.
I converted distances into light years and added galactic coordinates to the database. This site generates a star map of the selected area of space, and optionally displays the names of stars from a selected science fiction universe. Currently nearly 200 systems from Star Trek have been identified. Thanks to Jörg for identifying the majority of them.
Two sets of coordinates are stored for each star in the database. The equatorial (2000.0)
coordinates, which you can view by selecting a star, and the Galactic
Cartesian coordinates. The equatorial coordinates determine the two-dimensional
location of a star in the sky. Select Romulus, for example, and find its location in a star atlas,
and you will see that it is a dim star in the constellation Virgo. You'll need binoculars or a
telescope to actually see it.
The Galactic coordinates place the star in three-dimensional space. (0,0,0) is our Sun's coordinates. The positive X axis points toward the Galactic center, about 26,700 light years away or (26700,0,0). The positive Y axis points toward 90 degrees Galactic longitude, in the direction of the constellation Cygnus. And the Z axis points "up" out of the Galactic plane, toward Coma Berenices.
On the screen, the positive X axis is up toward the top of the screen, Y to the left, and Z out of the screen toward the viewer. You're looking down on the galactic plane from above it.
You can choose a specific star from the table at the bottom of the screen. It will list only the
stars visible on the current map. After selecting a star, it will have a blue box around it on the
map and details will be displayed to the left of the map. If you check the "center on selection" box,
the map will also be moved so that the selected star is in the middle. Selecting a fictional star name
from the dropdown at the bottom will automatically center and select that star on the map.