star distance error

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Anonymous
2012-10-27
2013-07-17

  • Anonymous
    2012-10-27

    Hi
    I was playing with Sirius, searching its position in the past and in the future.
    I know Stellarium uses star's proper motion in order to compute star positions, but what about the star distance?
    Sirius now is at 8.60 light years from us.
    Suppose we jump into the future at 32012: its position changes, but the distance remains 8.60 ly.
    The same happens for the year -32012... and happens also for other stars: I checked with Alpha Centauri and its distance is always 4.39 light years :-(

    don't you think it's a bug?
    Pierluigi

     
  • Alexander Wolf
    Alexander Wolf
    2012-10-27

    Stellarium displays distance for stars from catalogs, not from calculations.

     

  • Anonymous
    2012-10-28

    OK!
    So I think it should be corrected! Don't you?
    It's wrong to display mixed infos: positions (RA/decl, HA/DE, Az/Alt) are computed for the new date while the distance (and now I suppose also magnitudes and parallax) is for the current date!
    Pierluigi (from Italy)

     
  • Alexander Wolf
    Alexander Wolf
    2012-10-28

    If you can build full 3D map of Universe then welcome. Also you need reading about astronomical coordinates systems because you don't understand it's.

     
  • Bogdan Marinov
    Bogdan Marinov
    2012-10-28

    Not only Stellarium's proper motion does not include distance, it also doesn't reflect the actual trajectories of stars as it extrapolates the motion linearly instead of creating a 3D gravitational simulation of the Milky Way galaxy.

    If you know an easily accessible star catalogue that provides proper motion correction in three dimensions, please tell us about it.

    So I think it should be corrected! Don't you?

    No, I don't think that it should be corrected, or at least that it should be in the top 100 things to do on Stellarium right now. Stellarium's prime purpose is to serve as an educational tool and an aid to amateur astronomers, not as an ultimate model of the Galaxy for the past and the future.

     

  • Anonymous
    2012-10-28

    thanks for the answers.
    Alexander, I'm fond of Astronomy since 1969, so I think I know and understand perfectly astronomical coordinates systems. Why do you think I don't understand them?? :-O

    I'm using Stellarium from many many years, I appreciate it everytime and I always suggest its usage to all the readers of the internet site I write for. In the past years I also contributed for bugs and for other requests... I don't know why I can't access this forum with the old username/password...

    Don't correct anything, please, but how can I explain to my readers why the star position is "correct" for past and future years while the position is incorrect?
    It's like having a good car but with one missing wheel...
    :-(
    So why do you use proper motion model if you are not confident with it's characteristics? It could be better not to use proper motion at all, instead of using it "at half speed". Celestia programmers simply don't use it

     
  • Alexander Wolf
    Alexander Wolf
    2012-10-29

    OK. If you are old astronomy amateur then you should understand: we can't calculate correctly distance to stars without knowledge about 3D coordinates of those stars (and parallaxes, of course).

     
  • Timothy Reaves
    Timothy Reaves
    2012-10-29

    I too would like to see the objects positions displayed as accuratly as possible. That is just not possible with the current code base, due to the design decisions made when the app was first created. And we simply do not have the people involved we'd need to, to rewrite such a significant amount of code.

     

  • Anonymous
    2012-10-29

    So... why do you consider the star's proper motion? simply neglect it and say that stellarium doesn't use proper motion... it's easier... it's error proof and doesn't produce errors... and users ar not fooled!!

    the proper motion as expressed in Simbad is only a snapshot of the actual situation (it's not a polynomial but a simple formula) so it shouldn't be used for computing positions in the past and in the future! and it shouldn't even be allowed to...
    my suggestion is to forget about it :-( at least up to a new modelling of proper motion.

     
  • Alexander Wolf
    Alexander Wolf
    2012-10-29

    Stellarium used simple linear model for proper motion of stars and this model give educational examples about stars motion and view of constellation in time. Not very accurate but this better then nothing.

    If you need more accurate positions of stars in time then you need use special scientific software.

     
  • abrik
    abrik
    2012-12-17

    Sorry. I wrote those people several mails, which have never been answered.
    I didn´t reset my account, i even deleted it,
    although i wouldn´t have, if this annoyance would not be happening,
    because i appreciate the Stellarium program.

    I try to set up a spam filter in Opera, maybe i will get rid of all those
    threads. Not that i would not read in the forums
    sometimes, but Sourceforges support ist just ridiculous.

    Thanks for the patience and greetings

    Am 17.12.2012, 12:00 Uhr, schrieb Alexander Wolf alexvwolf@users.sf.net:

    abrik, if you can't unsubscribe then ask sourceforce support team - WE
    DON'T HAVE ACCESS TO YOUR PROFILE.
    P.S. Did you tried reset your profile?

    star distance error

    Sent from sourceforge.net because you indicated interest in
    https://sourceforge.net/p/stellarium/discussion/278769/

    To unsubscribe from further messages, please visit
    https://sourceforge.net/auth/prefs/

     
  • abrik
    abrik
    2012-12-17

    Like i said, i have removed it already, or at least inactive (that´s what
    it says, when i try to log in).

    As far as i remember, i use only one account in SourceForge, and there are
    only mails referring to Stellarium topics,
    so it seems pretty obvious.

    I apologize for having gotten unfriendly, but i have tried a lot of
    things, like sending SF several mails,
    begging them to look into what is going wrong. I will see, if want to set
    an IRC client to ask those guys
    directly. Thanks again,

    Andreas

    Am 17.12.2012, 12:12 Uhr, schrieb Ross rosariorusso@users.sf.net:

    abrik, try to remove the account: https://sourceforge.net/account/remove
    If it does not work, try to contact directly the SourceForge staff via
    IRC. Are you sure >you don't have another account in SourceForge?
    Perhaps that account is receiving >the "spam".

    star distance error

    Sent from sourceforge.net because you indicated interest in
    https://sourceforge.net/p/stellarium/discussion/278769/

    To unsubscribe from further messages, please visit
    https://sourceforge.net/auth/prefs/

     
  • Jerome Colburn
    Jerome Colburn
    2013-01-07

    Am I correct in inferring that the reason Stellarium doesn't do this is that the original catalog doesn't include a radial velocity field?

     
  • Alexander Wolf
    Alexander Wolf
    2013-01-08

    Of course, we have a limited data from catalogs. If you can improve catalogs and calculations of property motions of stars then welcome - you need register on launchpad.net, make a branch and add code and data.

     
  • VReijs
    VReijs
    2013-01-19

    I think there are no catalogues that ave the distance as part of proper motion proper motion. I think no instrument yet has really measured that changing distance (although Einstein might have an idea: the enlargement of the universe(s?).

     

  • Anonymous
    2013-01-23

    Hi,

    I am interested in creating or having someone else create a constellation's change over time, perhaps 100,000 to 1,000,000 years ago to now. I came across this post that seems to be on that subject. I don't, frankly, care that it be more than superficially "accurate" (in terms of the changing distance and trajectories of the stars involved in space in the calculation as is the original poster) as it is for a fictional piece of work. Is this something easy to do if I download the program? Is it something others have done and would be willing to share?

    Jonathan

     


Anonymous


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