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Inconsistency in C/2011 L4 elements

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  • lowe4091
    MPEC 2011-M31 was issued today with revised elements for C/2011 L4. The inclination is indicated as 93.71, yet my own calculations with Find_Orb show
    Message 1 of 4 , Jun 24 7:31 PM
      MPEC 2011-M31 was issued today with revised elements for C/2011 L4. The inclination is indicated as 93.71, yet my own calculations with Find_Orb show i=84.92+/-0.78. Likewise, the MPC gives the time of perihelion as 2013 Mar 26.4, yet Find_Orb computes 2013 Mar 11.6+/-1.4.

      While I believe the MPC weights the astrometry according to observing site, it's hard to imagine that there could be such a difference between the two sets of calculations.

      Anyone have an independent estimate of the inclination and perihelion date?

      Andrew
      http://members.shaw.ca/andrewlowe/home.htm
    • terryjlovejoy
      Hi Andrew, Actually I tried putting the available positions into find_orb and I also get T=2013 Mar 11.7, i=85.0. I m not sure what the story is.. Terry
      Message 2 of 4 , Jun 24 11:39 PM
        Hi Andrew,

        Actually I tried putting the available positions into find_orb and I also get T=2013 Mar 11.7, i=85.0. I'm not sure what the "story" is..

        Terry
      • Maik Meyer
        Hello all, ... just send an e-mail to the MPC. The orbit has been derived automatically, so there might be a bug or something. Gareth will take care. Cheers,
        Message 3 of 4 , Jun 25 1:35 AM
          Hello all,

          > Actually I tried putting the available positions into find_orb and I also get T=2013 Mar 11.7, i=85.0. I'm not sure what the "story" is..

          just send an e-mail to the MPC. The orbit has been derived automatically, so there
          might be a bug or something. Gareth will take care.

          Cheers, Maik
          --
          If they give you ruled paper, write the other way. * Juan Ramon Jimenez
          ________________________________________________________________________
          maik@... http://www.comethunter.de
          German Comet Section http://www.fg-kometen.de
          http://groups.yahoo.com/group/comets-ml
        • pachacotihui
          I also tried to feed thus far all astrometric data to FindOrb with rejection to eight obs whose residuals is larger than 1 arcsec, and obtained a similar
          Message 4 of 4 , Jun 25 2:46 AM
            I also tried to feed thus far all astrometric data to FindOrb with rejection to eight obs whose residuals is larger than 1 arcsec, and obtained a similar solution like yours that distinguishes the one in MPEC-M31 at perihelion date and inclination:

            C/2011 L4
            Perihelion 2013 Mar 11.384032 TT; Constraint: e=1
            Epoch 2011 Jun 24.0 TT = JDT 2455736.5 Earth MOID: 0.6674 Ju: 0.0448
            q 0.30233065 (2000.0) Me: 0.0128
            M(N) 5.9 K 10.0 Peri. 333.64222 0.40670190 0.10877897
            Node 65.62443 0.90934769 0.04704388
            e 1.0 Incl. 84.76578 -0.08763751 0.99295216
            From 81 observations 2011 May 21-June 24; RMS error 0.518 arcseconds

            Cheers, Man-To
            --- In comets-ml@yahoogroups.com, "lowe4091" <andrew.lowe@...> wrote:
            >
            > MPEC 2011-M31 was issued today with revised elements for C/2011 L4. The inclination is indicated as 93.71, yet my own calculations with Find_Orb show i=84.92+/-0.78. Likewise, the MPC gives the time of perihelion as 2013 Mar 26.4, yet Find_Orb computes 2013 Mar 11.6+/-1.4.
            >
            > While I believe the MPC weights the astrometry according to observing site, it's hard to imagine that there could be such a difference between the two sets of calculations.
            >
            > Anyone have an independent estimate of the inclination and perihelion date?
            >
            > Andrew
            > http://members.shaw.ca/andrewlowe/home.htm
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