The Astronomy Nexus

The Encyclopedia of Suns includes some information about stars' positions in space. Each star has the following
information included:

  • Right Ascension and Declination. These coordinates are analogous to longitude and latitude on the Earth: right ascension measures a distance "around" the sky, and declination distance "north" or "south". For historical reasons, right ascension is normally given in hours rather than degrees, where one hour equals 15 degrees. Thus right ascensions run from 0 to 24 hours.

    You can use the right ascension and declination in the Encyclopedia of Suns to locate each star on a star atlas chart.

  • Finder Chart. Each star has a finder chart showing the area of sky around it. If you're familiar with the night sky, you can use these charts directly to find each star in the sky. In general, the charts are oriented with north at the top.

    The charts have a limiting magnitude of +7.5. Under a very good sky, the dimmest chart stars are just visible to someone with good night vision, without binoculars or a telescope. From a city, the faintest stars in the charts can be seen in small binoculars (25 to 35 mm diameter lenses). Since many of the Encyclopedia stars are only slightly brighter than this limit, they will not be easy to see from a city without optical aid.

  • Distance. This is given in light years. If you prefer to use parsecs, divide the distance by 3.26.

  • XYZ Coordinates The star's coordinates, also in light years, in a Cartesian coordinate system centered on the Sun.

    For the curious, the X-axis points to right ascension 0, declination 0 (the vernal equinox or "first point of Aries"), and the Z-axis points to the north celestial pole (near Polaris, the North Star). The Y-axis is at right angles to the other two and the overall coordinate system is right-handed.

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