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Ecliptic Grid

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xalixo
2010-08-19
2014-08-13
  • xalixo
    xalixo
    2010-08-19

    Is there any way to display an ecliptic grid in stellarium. I noticed it has
    been mentioned on launchpad https://blueprints.launchpad.net/stellarium but I'm not sure if its going ahead.
    Would it be possible to write a script for it? I'll try and do it myself if I
    have to but I don't know how hard it would be to do, and I would have to learn
    how to do it. Can anyone give any advice on what needs to be done to get this
    function in stellarium? Thanks, xalixo.

     
  • Martin Lewicki
    Martin Lewicki
    2010-08-20

    I asked about putting in ecliptic coordinates in the past but came against a
    brick wall. It appears the programmers here are a bit lopsided phobic about
    adding this because ecliptic = tropical zodiac = astrology = encouraging
    "superstitious nonsense". This is rather curious as almost every other
    planetarium software has an ecliptic coordinate function eg Skymap Pro and
    Ciel du Cartes etc. and ecliptic coordinates appeared in historical
    uranography like the maps of Bayer and and Jamieson.

    Martin

     
  • barrykgerdes
    barrykgerdes
    2010-08-20

    Hi

    The addition of eclipic coords is not in the current program of development
    mainly because there are other necessities to do first. The other free
    programs probably have someone interested like you to add the necessary code.
    The commercial programs have this because they see a market and can invest the
    necessary money to comply.

    However there is nothiing to stop you adding your own version. If you cannot
    do this yourself you may be able to hire a programmer to do it for you.

    Barry

     
  • Martin Lewicki
    Martin Lewicki
    2010-08-21

    Hi

    Since we use Stellarium with Mirrordome system at the Adelaide Planetarium,
    having the ecliptic coordinate would indeed be useful when teaching describing
    planetary motion in our courses. At any rate if and when the programmers get
    around to it perhaps they could do both ecliptic and galactic grid at once.

    Martin

     
  • xalixo
    xalixo
    2010-08-22

    Thanks for the replies.

    Looks like it'll be a few years until the programmers do it, and I doubt it'll
    be a simple procedure of just adding a small script. I'm too skint to pay a
    programmer and I only know some very basic programming myself, so I'm going to
    try and learn a bit more, but it'll take me ages before I'm skilled enough to
    do anything for Stellarium. I agree it'd be a very good idea to do an ecliptic
    and galactic grid simultaneously. Maybe even an ecliptic mount could be added,
    or is that a bit over the top? Anyway I suppose it'll be a while yet before we
    get any of these functions.

    xalixo.

     

  • Anonymous
    2014-08-11

    By now the ecliptic and galactic coordinate grids have been added, however their corresponding mounts are still missing. The mounts are also necessary, because one only can achieve a proper orientation of the sky map from a certain coordinate system's point of view if its aequator can be kept horizontally leveled. The azimuthal mount keeps the location's horizon horizontally leveled, and the aequatorial mount keeps the projection of the Earth's aequator onto the celestial sphere horizontally level. Now, mounts are needed so that the ecliptic as well as the great circle of the galactic plane (aequator of the galactic coordinate system) can be kept horizontally leveled if so desired.

     
    • Alexander Wolf
      Alexander Wolf
      2014-08-11

      Are you have mount with support galactic or ecliptic coordinates?

       

      • Anonymous
        2014-08-11

        I don't have physical observation gear which would mount using the ecliptic or galactic coordinate systems, if that's the question. But, that's not really the point. The requested mounts would help make the ecliptic and galactic coordinate grids much more comfortable to use, because, as explained above, with a proper mount the great circle which is the aequator of the given coordinate system will stay level when moving the viewport around, rather than tilting weirdly which is the case with a mount corresponding to a different coordinate system.

        For the azimuthal coordinate system to make sense, the azimuthal mount is necessary, so that the aequator of the system (in this case the local horizon) always stays horizontal, and the poles (in this case zenith and nadir) always can be approached by vertical movement of the viewport. The other currently existing mount allows the aequatorial coordinate system can work the exact same way (which is most useful to me personally when using Stellarium as a sky map rather than a planetarium, i.e. with ground, atmosphere, etc. turned off).

        Corresponding mounts for the other two coordinate systems would allow to properly orient the celestial sphere in terms of the currently preferred coordinate system, i.e. to have the aequator (ecliptic for ecliptical coord. system and galactic plane great circle for galactic coord. system) always remain horizontal and the poles remain at the "top" and "bottom". While admittedly this would probably not be terribly useful for observational purposes, it would arguably come very handy for educational purposes. Also, given that all four coordinate systems are already implemented and mounts for the first two exist, it probably would be possible to reuse existing mount code so that new options orient the celestial sphere in terms of the other two coordinate systems.

        Thus, while understandibly not nearly a matter of priority, it should be fairly straightforward to implement with the existing features already in place, and would be a nice and useful (while admittedly perhaps more "exotic") addition to the program.

         

  • Anonymous
    2014-08-11

    Not really, but mount options for the other two coordinate systems would allow to properly orient the celestial sphere in terms of the given coordinate system (rather than have its aequator and poles tilt weirdly when panning the viewport) when using Stellarium as a skymap, i.e. with ground, atmosphere, etc. disabled. It just makes most sense to have the aequator stay horizontal and the poles stay at the "top" and "bottom", that's why we have mounts for the first two coordinate systems.

    Given that all four coordinate systems, as well as general mount logic that orients the celestial sphere in terms of a given coordinate system are all implemented, it should now be fairly easy to add options for ecliptic and galactic mounts as well. While certainly not a priority feature, it's arguably useful and it'd be a great thing to have in the program.

     

  • Anonymous
    2014-08-11

    (I'm sorry for essantially posting the same arguments twice; when submitting the first post I initially got a 500 error and thought what I wrote was lost, so I recapped it in another post.)

     

  • Anonymous
    2014-08-13

    Hello again,

    here's an example which hopefully makes it very clear why every implemented coordinate system really needs a corresponding "mount" to be fully usable.

    The attached image shows a Mercator-style sky map I arranged showing the brightest stars in our sky. The coordinate system is equatorial; its grid is perfectly rectangular, the equator is horizontal and, logically enough, the vernal point (being the origin of the employed coordinate system) is at the center of the map.

    Unfortunately, it is impossible to arrange a corresponding map based upon the galactic coordinate system. Because the latter currently has no "mount" which would keep the map properly oriented in terms of that coordinate system, the galactic grid cannot be kept rectangular for an arbitrary horizontal shift of the map (of course, it would be desirable to have the origin of the galactic coordinate system in the center).

    The above is naturally also true for any other projection, I chose to use Mercator in the example for clarity. The goal is to be able to keep the fundamental plane of any currently preferred coordinate system horizontal, and it's axis vertical, with the poles remaining stationary. This is precisely what a "mount" corresponding to a given coordinate system does.

    Another note: for completeness' sake, the supergalactic coordinate system would be wery welcome to see implemented as well (of course complete with a "mount"). While probably not terribly useful to most users, there is really no reason not implement it along with the other four systems established in spherical astronomy. It comes especially handy when contemplating the distribution of nearby galaxies and other cosmological matters.

    (It is worth remembering that the more "obscure" a coordinate system is, the more universal it actually is. The horizontal system for the observer's current location is the most intuitive, but loses relevance once we move to another location on the celestial body we currently reside on. The an iteration of the equatorial system is specific to the current orientation of the Earth's axis, and loses relevance once the axis has precessed too much, or the observer leaves the Earth altogether. The ecliptical system stays relevant for as long as the observer resides in the Solar System. On the other hand, for the galactic or supergalactic systems to become irrelevant, the observer would need to go as far as, respectively, leaving our galaxy, or the local supercluster.)

     


Anonymous


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