Eris possition wrong

Feedback
2009-02-25
2012-10-09
  • Martin  Lewicki
    Martin Lewicki
    2009-02-25

    Positon of Eris in 0.10.1 is wrong. Does not match NASA

    I can't make sense of some of the orbital element entries in ssytem.ini for Eris. A mess format. Tried various ways of putting Eris elements from NASA Small-Body Database to no avail - still wrong position.

    http://ssd.jpl.nasa.gov/horizons.cgi

    http://ssd.jpl.nasa.gov/sbdb.cgi#top

    Marty

     
    • barrykgerdes
      barrykgerdes
      2009-02-25

      I am using

      [eris]
      name = Eris
      parent = Sun
      radius = 1300
      oblateness = 0.0
      albedo = 0.689
      lighting = true
      orbit_visualization_period = 204376.01809
      halo = true
      color = 1.0,1.0,1.0
      rot_periode = 8
      tex_halo = star16x16.png
      tex_map = nomap.png
      coord_func = comet_orbit
      orbit_Epoch = 2454800.50
      orbit_MeanAnomaly = 198.858225
      orbit_SemiMajorAxis = 67.902798
      orbit_Eccentricity = 0.4361532
      orbit_ArgOfPericenter = 151.51961
      orbit_AscendingNode = 35.95741
      orbit_Inclination = 44.022944

      This appears to be tha latest informaton

      This apparently earlier data

      [eris]
      name = Eris
      parent = Sun
      radius = 1300
      oblateness = 0.0
      albedo = .689
      lighting = true
      orbit_visualization_period = 203603
      halo = true
      color = 1.0,1.0,1.0
      tex_halo = star16x16.png
      tex_map = nomap.png
      coord_func = comet_orbit
      orbit_Epoch = 2454200.5
      orbit_MeanAnomaly = 197.96
      orbit_SemiMajorAxis = 67.732
      orbit_Eccentricity = 0.4400
      orbit_ArgOfPericenter = 151.56
      orbit_AscendingNode = 35.8844
      orbit_Inclination = 44.1595

      Puts Eris about 5 arc secs further north

      Barry

       
    • barrykgerdes
      barrykgerdes
      2009-02-26

      Hi Hendrik and Martin

      The svn has now been updated with the revised data for Eris Using the later parameters provided by Hendrik. Which seems to give the correct results. Certainly near enough to locate in a 1 arc minute field

      Barry

       
    • barrykgerdes
      barrykgerdes
      2009-02-25

      The orbital elements in the ssystem.ini file were obtained some time ago and could be way out particularly with the ell_orbit algorithm. I entered the orbital params from the reference and this placed Eris at 2hr18m41.3s +1d10m9.5s but I cannot confirm where it actually is.

      Barry

       
    • Kird
      Kird
      2009-02-25

      Try these values for the orbital elements:

      [eris]
      name = Eris
      parent = Sun
      radius = 1300
      oblateness = 0.0
      albedo = 0.367
      lighting = true
      orbit_visualization_period = 204376.01809
      halo = true
      color = 1.0,1.0,1.0
      rot_periode = 8
      tex_halo = star16x16.png
      tex_map = nomap.png
      coord_func = ell_orbit
      orbit_Epoch = 2454800.50
      orbit_SemiMajorAxis = 67.902798
      orbit_Eccentricity = 0.4361532
      orbit_Inclination = 44.022944
      orbit_AscendingNode = 35.95741
      orbit_LongOfPericenter = 151.51961
      orbit_MeanLongitude = 198.858225

       
    • barrykgerdes
      barrykgerdes
      2009-02-25

      Hi Kird

      They are almost the same as what I have
      Where does that put Eris at the moment

      Barry

       
    • Kird
      Kird
      2009-02-25

      I didn't notice, but the section for Eris is completely messed up.
      The names for the orbital elements are wrong. It should be:
      [eris]
      name = Eris
      parent = Sun
      radius = 1300
      oblateness = 0.0
      albedo = 0.367
      lighting = true
      orbit_visualization_period = 204376.01809
      halo = true
      color = 1.0,1.0,1.0
      rot_periode = 8
      tex_halo = star16x16.png
      tex_map = nomap.png
      coord_func = comet_orbit
      orbit_Epoch = 2454800.50
      orbit_MeanAnomaly = 198.858225
      orbit_SemiMajorAxis = 67.902798
      orbit_Eccentricity = 0.4361532
      orbit_ArgOfPericenter = 151.51961
      orbit_AscendingNode = 35.95741
      orbit_Inclination = 44.022944

      This puts Eris in Cetus near Mira (though you have to zoom in a million times to see Mira).
      I'm not sure about the coord_func. Should it be el_orbit or comet_orbit?

      Hendrik

       
    • Kird
      Kird
      2009-02-25

      It's comet_orbit. When you use ell_orbit Eris is behind the Sun ans stays there, even when you change the date.

       
    • barrykgerdes
      barrykgerdes
      2009-02-25

      Hi Hendrik

      Using your ellements in comet_orbit puts Eris at 1hr37m17.5s
      -4d38m36s

      I used the elements from the reference in ell_orbit and got Eris at 2hr18m41.3s +1d10m9s

      I noted that ell_orbit with your params centres on the sun.

      What I don't know is the true position for Eris. I haven't found a site that gives them yet.

      Here is what I used

      [eris]
      name = Eris
      parent = Sun
      radius = 1300
      oblateness = 0.0
      albedo = 0.367
      lighting = true
      orbit_visualization_period = 2.041162179748626E+05
      halo = true
      color = 1.0,1.0,1.0
      rot_periode = 8
      tex_halo = star16x16.png
      tex_map = nomap.png
      coord_func = ell_orbit
      orbit_Epoch = 2456282.469734213620
      orbit_Period = 2.04376018098831855955E+05
      orbit_SemiMajorAxis = 9.751882097335734E+9
      orbit_Eccentricity = 4.361532020451209E-01
      orbit_Inclination = 6.790279813775292E+01
      orbit_AscendingNode = 3.828677530214852E+01
      orbit_LongOfPericenter = 198.858250539009
      orbit_MeanLongitude = 35.95740654774798

      Barry

       
    • Kird
      Kird
      2009-02-25

      I got these values from the NASA site as Martin had looked there. But in my opinion the best site for orbital elements (for asteroids and for comets) is the Minor Planet Center.

      http://www.cfa.harvard.edu/iau/Ephemerides/index.html

      http://www.cfa.harvard.edu/iau/Ephemerides/Distant/D6199.html

      http://www.cfa.harvard.edu/iau/Ephemerides/Comets/index.html

      http://www.cfa.harvard.edu/iau/mpc.html

      http://www.cfa.harvard.edu/iau/info/OrbElsExplanation.html

       
    • Kird
      Kird
      2009-02-25

      This ephemeris is from the MPC-site. R.A. 1 37 and Dec -04 38 are the right values.

      Date TT R. A. (2000) Decl. Delta r Elong. Phase V
      2009 02 08 01 36.91 -04 43.8 97.184 96.730 62.3 0.5 18.8
      2009 02 13 01 37.00 -04 42.4 97.256 96.729 57.5 0.5 18.8
      2009 02 18 01 37.10 -04 41.0 97.325 96.728 52.7 0.5 18.8
      2009 02 23 01 37.22 -04 39.5 97.388 96.728 47.9 0.4 18.8
      2009 02 28 01 37.35 -04 38.0 97.447 96.727 43.2 0.4 18.8
      2009 03 05 01 37.49 -04 36.5 97.500 96.726 38.6 0.4 18.8
      2009 03 10 01 37.64 -04 35.0 97.547 96.726 34.0 0.3 18.8

      These positions agree with those from other sites and other planetarium programs.

      Hendrik

       
    • barrykgerdes
      barrykgerdes
      2009-02-25

      Yes those positions agree with this

      [eris]
      name = Eris
      parent = Sun
      radius = 1300
      oblateness = 0.0
      albedo = .689
      lighting = true
      orbit_visualization_period = 203603
      halo = true
      color = 1.0,1.0,1.0
      tex_halo = star16x16.png
      tex_map = nomap.png
      coord_func = comet_orbit
      orbit_Epoch = 2454200.5
      orbit_MeanAnomaly = 197.96
      orbit_SemiMajorAxis = 67.732
      orbit_Eccentricity = 0.4400
      orbit_ArgOfPericenter = 151.56
      orbit_AscendingNode = 35.8844
      orbit_Inclination = 44.1595

      Barry

       


Anonymous


Cancel   Add attachments