Lunisolar precession per 25.920 years

  • Ata

    Ata - 2004-11-29

    First of all congratulation for this excellent and exact work (v0.6.2), but I observed a little time deviation (~ 1 hour) during the simulation of Venus transit in 08.06.2004 which should start at 5:32 UT (phase 2) and end at 11:06 UT (phase 3).
    Regarding the lunisolar precession if anybody would like to jump in the time (some 1000 years) and would like to see correct positions of the stars you have to take the lunisolar precession into consideration which has 25.920 years periodicity (acc. to description of Egypt Horus Eye clergy, maybe you have more exact info).
    As I know during this 25.920 years the sun revolves round and therefore the North Pole Star is always has changing. Now the Polaris is our Pole Star for about 4000 years, in really the “theoretical North Pole” always moving on a circle. If you need some help for this solution I found a program (Home planet v3.1 – which use the lunisolar precession and the position of Pole Star (not Polaris) also moving, but it use the Julian date and for this reason it’s impossible to input older date then –4712 year (begin of Julian date).
    I think that is the best solution if you can calculate with lunisolar precession where the North Pole always can moving and you should to solve the data input by manually not just by click! For example all necessary data (location data, year, month and day) can be input by manually and in my opinion please keep this time format (not Julian date).
    After this everybody could be input whatever date (e.g. 2004.06.06 or –8243.12.09) and the positions of all stars will be repeat per 25.920 years. Afterwards we also will able to check the star positions when the Sphinx or Great Pyramid built… :)

    • Ata

      Ata - 2005-11-06

      Dear Stellarium maker team,

      As you also agreed the precession circle is a good idea (see formerly), so when do you plan to implement it? Some additional idea for this: it would be more professional when a little cross will mark the theoretical Nort Pole on this precession circle which pass round on this circle during 25.920 year.

      In additional the most professional solution is that if you display the RA and DE coordinates of this mentioned little cross point. It is a good and helpful data for the calculations of other stars's positions in a 3D coordinate system...
      (Please find my bug reports in the "Bug reports" topic for the precession motion).

      Best regards,

    • Rob Spearman

      Rob Spearman - 2004-11-29

      We actually have precession of the equinoxes working in the CVS main branch if you want to try that. (It's a lot easier!)

      If you want to type in dates, you can enable the tui (text user interface) by setting flag_enable_tui_menu to true in your config file. You bring up the menu with the 'm' key and navigate with the arrow and enter keys.

      This is a workaround until we find a better GUI library that will make UI work easier.

      • Nobody/Anonymous

        I enable the tui's to "true" eg

        flag_enable_tui_menu = true

        ran program, typed "M", scrolled through with arrow keys, found the time change but no date change???

        At any rate program crashes for dates before 1970!


    • Ata

      Ata - 2005-04-26

      Hello Rob Spearman,

      In the past I also tried to change the date with extra settings which you mentioned, but I did not observed any precesion motions of the stars. So, in this way I could not examine the positions of the stars (mainly the North Star) e.g. 2000 years ago.
      I think if you will implement the precession motion per 25.920 year in your next progam version, it would be better when you mark the precession circle on the sky (mainly across North stars) like ecliptic line with button "4".

      • Rob Spearman

        Rob Spearman - 2005-04-26

        You need to download and compile the Stellarium version in CVS (version 0.7.0) to observe precession.

        It does not drarw a precession circle currently, but that is a good idea.

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    Anonymous - 2016-07-09

    Hi excellent program!
    Can you tell me what rate of precession you use in Stellarium and whether this is fixed or variable?

    • Alexander Wolf

      Alexander Wolf - 2016-07-09

      Quote from description of version 0.14.0:

      V0.14 brings a big leap forward in astronomical accuracy for historical applications:
      - Precession now follows the IAU2006 model in the long-time version from Vondrák et al. 2011.

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        Anonymous - 2016-07-12

        thanks for the info! :)

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      Anonymous - 2016-07-09

      Funny to read about the state of the program from the days of its infancy more than a decade ago in such reanimated threads...
      Yes, Vondrák 2011 since V0.14, so rate is no longer fixed.

      Last edit: gzotti 2016-07-09


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