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  1. How did you choose which stars were labeled on the reference charts? They don't seem to be in any real order.

    I chose to focus on stars that are relatively close to the Sun, since these show up most dramatically in the stereo plots and the animations. The labeled stars (marked with a yellow cross and a name or catalog designation) are all stars within 12 parsecs (about 40 light years), according to the data in Hipparcos.

  2. What are the catalog names / numbers you use in the reference charts and Distant World renditions?

    Most stars have been cataloged numerous times, by astronomers with differing interests and needs. Because of this most stars have a number of names they can go by. In 3D Universe, I've had to use quite a few different names and designations. Here's a list of the sources I used, in order of decreasing preference.

    • Common Names: These are names, usually from Arabic or Latin, that derive from names early astronomers bestowed upon the brightest stars. Many of the Arabic names come (with varying degrees of corruption over the centuries) from the Almagest, the Arabic translation of Ptolemy's writings. Examples, Sirius (the "Dog Star", brightest star in the sky), Pollux (one of the twins Gemini), and Denebola (the "tail" of the lion Leo). A few common names, such as "Proxima Centauri" or "Barnard's Star", are of very recent origin.
    • Bayer Designations: Devised by the 17th century German astronomer Bayer, who labeled the stars (usually roughly in order of brightness or position) in a constellation by Greek letters (alpha, beta, gamma, etc.). On charts, these consist of a Greek letter or letter name plus a three-letter abbreviation for the constellation. Examples: Alpha Centauri (Alpha Cen), Epsilon Eridani (Epsilon Eri).
    • Flamsteed Numbers:Named for John Flamsteed, a 17th-century English astronomer who published a star catalog and later a star atlas, both containing most of the brighter naked-eye visible stars. The French astronomer Joseph Lalande created a numbering scheme based on Flamsteed's catalog, which has persisted to this day: Lalande numbered Flamsteed's stars from west to east in each constellation. Examples: 61 Cygni (61 Cyg), 107 Piscium (107 Psc).
    • Harvard Revised (HR) Photometry numbers: the basic identification used in the Bright Star Catalog from Yale University. These numbers were assigned to approximately 9,000 stars of naked-eye brightness early in the 20th century, so most stars you can see in the sky without a telescope have an HR number. The Yale Bright Star Catalogue is also a very common source for astronomical data (it's freely available to the public, like Hipparcos), so many astronomy programs use it extensively. Examples: HR 222, HR 7703.
    • Hipparcos numbers (HIP): These are simply the numbers assigned to the stars observed by Hipparcos. Most stars identified by HIP numbers in 3D Universe are dim stars that lack identification in the other sources I've used.
    • Gliese Numbers: These are numbers assigned to nearby stars (within 85 light years, according to the best data at the time) by the German astronomer Gliese. These are usually indicated by "Gl" (for Gliese) or "GJ" (for Gliese-Jahreiss) followed by a number.
  3. What is the color scheme for the labels in Distant Worlds?

    In the ray-traced charts (the ones with the planetary systems), many stars are labeled by their name or catalog number:

    Red: Common Name (as distinct from catalog number)
    Yellow: The Sun
    Orange: A bright star (apparent mag. < 2.0)
    Green: A nearby star (distance < 6.0 parsecs or 20 light years)

    The Sun is always labeled with yellow, regardless of distance or brightness. For other stars, nearby stars are always labeled with green, regardless of brightness, and bright stars that are not near are always labeled with orange. Red is reserved only for stars with a common name (i.e., something other than a Bayer Greek letter, Flamsteed number, or other catalog designation) that don't fall into one of the other categories.

    The Distant Worlds Star Mapper uses a similar color scheme, except that it has many more proper names. To avoid clutter, proper names are displayed only if the star is bright (orange, as above), or near (green, as above); there are no red labels. Unlike the ray-traced samples, the brightness and distance limits aren't fixed; the user can choose any desired brightness or distance cutoff.

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