-----BEGIN PGP SIGNED MESSAGE----- The Yale Stars (by Peter Chambers) October 2000 The Yale stars (yale.map) is a star map for VGAPlanets, a strategy game of the play by e-mail sort. The yale stars are derived from the Yale Bright Star Catalogue rev.3 (1980) which is a list of 9110 stars which are a compilation of bright stars taken from astronomical sources. The sub-set used for this "map" are transformed from the list by software using the following criteria: - - - the star must have a constellation identifier (e.g. alpha Centauri) - - - there must be a distance estimate (trig. or spectral parallax) - - - the distance must be within about 200 light years - - - RA and Dec figures for epoch 2000 must be available - - - there must be a star type (colour) listed The figures for RA and distance are (ab)used to create X, Y co-ordinates for the map. X = 10 * cos(RA) * distance Y = 10 * sin(RA) * distance properly in geocentric astronomy x = cos(Dec) * cos(RA) * distance x = cos(Dec) * sin(RA) * distance x = sin(Dec) * distance Declination (Dec) is simply ignored. The factor of 10 is used as the travel times of VGAPlanets ships require a larger physical universe then ours! Many stars with commonly known names are missing. Wolf 359 seems a favourite with VGAP players. This is because they do not appear in bright star maps. Wolf 359, for instance, has a brightness relative to the sun of 0.00002. Barnard's star is slightly better at 0.00044. The figure for Wolf 359 is about 5 decades lower than solar brightness. Human sight can cope with 4 decades of brighness going from bright sunlight to a room inside. Mid-day under Wolf 359 on a hypothetical terrestrial planet there would look gloomy to us. We could not grow crops there. Also since dim stars can be seem close up a map like this would have a cluster of dim stars close by Sol but none elsewhere. Tough. The constellation names are augmented by a choice of "traditional" names (e.g. Sirius, Formalhaut) if available or made-up ones if no traditional name is known. This list is partly donated, partly made up by me using a notebook and partly raided from the net by stripping words from websites which looked suitably geographic to google. Under the rule of fair use this extraction small enough to not be in copyright violation. And, after all, information wants to be free. The following resources from the www were raided for this work. http://www.entrenet.com/mizar/nearstar.html http://adc.gsfc.nasa.gov/adc/ http://www.stdimension.de/int/Cartography/IntroTools.htm http://aurora.phys.utk.edu/~daunt/study_guides/StellarProperties.html http://www.iau.org/ I have also obtained tha latest revision of the Yale stars and a list of stars within 25 parsecs of Sol. That's for later. The print book Philps' Atlas of the Universe came in handy for checking. In the process I learned just what a ragbag of errors star catalogues are. Each reputable one comes with an errata list in which the corrections made since last time are listed. Also listed are the entries which are dubious. There are transcription errors and observation errors. There is no checking by official sources as visual astronomy is now mainly amateur. The professionals are interested in X-ray or IR or satellites or Hubble. Amateurs want star catalogues so that they can know what they are looking at. The astronomers of history wanted catalogues to eliminate known stars from comets, clusters and what we now know are galaxies. Double star information in rev.3 is essentially useless due to lack of information, structure and star type information. Basically this makes star catalogues rather poor for our purposes. Since an astronomer is an observer on Earth looking at the celestial sphere their mental model is akin to a viewer in a planetarium. The information in a catalogue could be fed to a computer controlled projector with not much work. What we really want is a structured relational database of objects in space with relations modelled on physical assocations and attributes describing physcial parameters. This way multiple stars and visual doubles would be clearly distinguished. I doubt this will happend any century soon. NASA is looking at XML storage but the model of the observer in the sphere will inform the schema. This means that the star type in the MAP file is limited. I use the star colour code (G, K, etc) and absolute magnitude (from spectroscopy, etc) to map to one of the 21 VGAP star types. Some will never appear. There are no lone Neutron Stars known round here. Also multiple stars cannot be done with rev.3. I have tried. The star type mapping in now good enough for government work. This version does not (yet) include the "Dark Zone" nor any wormholes. A version called Yalexx may be produced (so named just by adding xx to the word Yale, ummmm). Don't hold your breath too long, doctors have said this is bad for your health. The files are released under the GNU Public License. The information they are derived from is in the public domain. Sites like NASA and the IAU note that the star catalogues have scientific value only. You should pass on these files to anyone who asks for them. I ask that you pass on the whole archive so that users can ask questions (and possibly demand better maps). I hope people use this map and enjoy the games. I like to think that players saying "I colonised Castor and Al Gieba then took Sol back from the Borg" may sound a little better than going to Mao 5 and The Daily Planet. This is not to knock Tim, who must have worked hard on Echo and Zeta. I just think our universe is bigger and more fun overall than a total creation. The more we can unbolt and plug into our simulations the better! Happy campaigning and smash the Borg! Peter Chambers -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.4 (GNU/Linux) Comment: For info see http://www.gnupg.org iQCVAwUBOfHSkjK3MBVrgsXxAQGaqAP/SlwbnHZ+897sXtANOLaunQxgAoGveWbW jVCDL56jDbYzXVvwEVt4IDmWMpkU2TphtufNv3uHWjil7TWhWGY4BUV0TY7k7tMI FfwDBhzaK4WENC1rbnOE4fQ/aGhRk3brK8502IodFynEa/49i3k+FZvfhVAg386f qUMFS7ePGGg= =+zR0 -----END PGP SIGNATURE-----