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Coordinate systems in the solar system?

  1. Feb 7, 2010 #1
    I have read the wikipedia page regarding Celestial coordinate systems and searched on google, but I cannot find any coordinate systems which describe a planet's position in it's orbit. Does there exist such a system?

    An example use of this system would be in locating the planets in the sky. I know that Mars is near opposition now, so I would expect that Mars' coordinates in such a system to be whatever Earth's position is +~180°.
  2. jcsd
  3. Feb 7, 2010 #2


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    Staff: Mentor

    That's an earth centered coordinate system, not a sun centered coordinate system. And it isn't how it typically works. The normal one uses the holds the background of stars fixed. It uses right ascention and declination. http://en.wikipedia.org/wiki/Celestial_coordinate_system

    What you suggest would hold the sun fixed. I guess something based on time would qualify, as the sun is due south at noon (therefore, Mars is due south at midnight right now).
  4. Feb 7, 2010 #3
    I did read that wikipedia article. But where can these coordinates for celestial objects be found, then? What is Mars' value at the moment, and where could I have looked that up myself?

  5. Feb 7, 2010 #4


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    Staff: Mentor

    Any decent planetarium program will give you the coordinates of an object. I use Starry Night.

    At this moment, Mars is at:
    RA: 8:39
    Dec: 23 degrees 3'
  6. Feb 7, 2010 #5

    D H

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    You might also want to read up on the International Celestial Reference Frame (ICRF, see http://rorf.usno.navy.mil/ICRF [Broken]) and Standards of Fundamental Astronomy (SOFA, see http://www.iausofa.org/index.html).

    As for coordinates for various bodies, the Horizons system at JPL is a very good reference. See http://ssd.jpl.nasa.gov/?horizons.
    Last edited by a moderator: May 4, 2017
  7. Feb 9, 2010 #6
    just something interesting:

    http://www.atticusrarebooks.com/jferg11.jpg [Broken]

    http://www.atticusrarebooks.com/jferg8.jpg [Broken]

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230432371491 [Broken]
    Last edited by a moderator: May 4, 2017
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