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Re: 2003 O2 orbit

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  • Juan Lacruz
    Maik, I confirm that some 704 residuals are way too bad, you can have a look at my calculation at http://www.geocities.com/juan_lacruz/mpec.htm Best regards,
    Message 1 of 8 , Aug 1, 2003
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      Maik,

      I confirm that some 704 residuals are way too bad, you can have a
      look at my calculation at

      http://www.geocities.com/juan_lacruz/mpec.htm

      Best regards,
      Juan.


      --- In comets-ml@yahoogroups.com, Maik Meyer <maik@c...> wrote:
      > Dear list,
      >
      > is it just me or is the LINEAR astrometry way, way BAD? The
      residuals of
      > the preliminary parabolic solution for half of the LINEAR
      observations
      > are up to 7 arcseconds of 34 observations only 25 were used --
      mainly
      > LINEAR observations were discarded...
      >
      > The comet may really be of short period as suspected in IAUC 8172
      > unfortunately I have found no likely value for e due to the short
      arc.
      > Because Sebastian is away on holidays I would appreciate to receive
      any
      > astrometry.
      >
      > Cheers, Maik
      >
      > P.S.: Peter, this is a great image!
      > --
      > If they give you ruled paper, write the other way. * Juan Ramon
      Jimenez
      >
      ______________________________________________________________________
      __
      > maik@c... http://www.comethunter.de
      > German Comet Section http://www.fg-kometen.de
      > http://groups.yahoo.com/group/comets-ml
    • Peter Birtwhistle
      ... residuals of ... observations ... mainly ... Maik, The LINEAR positions do look particularly bad. The coma is very diffuse and I ve just put another page
      Message 2 of 8 , Aug 1, 2003
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        --- In comets-ml@yahoogroups.com, Maik Meyer <maik@c...> wrote:
        > Dear list,
        >
        > is it just me or is the LINEAR astrometry way, way BAD? The
        residuals of
        > the preliminary parabolic solution for half of the LINEAR
        observations
        > are up to 7 arcseconds of 34 observations only 25 were used --
        mainly
        > LINEAR observations were discarded...
        >
        > Cheers, Maik

        Maik,

        The LINEAR positions do look particularly bad. The coma is very
        diffuse and I've just put another page up showing the difference
        between a single image and the full 15 image stack I posted yesterday:

        http://www.birtwhi.demon.co.uk/GalleryC2003O2_20030731_Coma.htm

        The coma has very little condensation on the single image - if there
        are any comet CCD observers that are going to submit astrometry on
        this one from single images I'd say grab a copy of Astrometrica (or
        simething similar) and stack your frames to increase S/N, otherwise
        the astrometry is likely to continue to show large residuals.

        Best regards,

        Peter
        J95
      • David Higgins
        What do you class way off ? I have been imaging Southern Comets and have found most around 0.2 to 0.6 off the MPC ephemeris position. I have been
        Message 3 of 8 , Aug 2, 2003
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          What do you class 'way off'? I have been imaging Southern Comets
          and have found most around 0.2' to 0.6' off the MPC ephemeris
          position. I have been reporting the Astrometry to the MPC (my plate
          solution residuals are 0.2" and my post fit residuals on minor
          planets/neo's is under 1" so I don't think it's my measurements.

          These include 116P, 77p, 65p, 66P, 53p, c/2002 L9, c/2003 KV2,
          c/2003 H2, c/2003 J1, c/2002 J4 whcih I have imaged and measured
          over the last 2 nights.

          Cheers

          David

          --- In comets-ml@yahoogroups.com, Maik Meyer <maik@c...> wrote:
          > Dear list,
          >
          > is it just me or is the LINEAR astrometry way, way BAD? The
          residuals of
          > the preliminary parabolic solution for half of the LINEAR
          observations
          > are up to 7 arcseconds of 34 observations only 25 were used --
          mainly
          > LINEAR observations were discarded...
          >
          > The comet may really be of short period as suspected in IAUC 8172
          > unfortunately I have found no likely value for e due to the short
          arc.
          > Because Sebastian is away on holidays I would appreciate to
          receive any
          > astrometry.
          >
          > Cheers, Maik
          >
          > P.S.: Peter, this is a great image!
          > --
          > If they give you ruled paper, write the other way. * Juan Ramon
          Jimenez
          >
          _____________________________________________________________________
          ___
          > maik@c... http://www.comethunter.de
          > German Comet Section http://www.fg-kometen.de
          > http://groups.yahoo.com/group/comets-ml
        • Maik Meyer
          David, ... I was not talking about pre-fit residuals. Look at the posted solutions. The residuals are from observations within a solution - post-fit residuals.
          Message 4 of 8 , Aug 2, 2003
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            David,

            > What do you class 'way off'? I have been imaging Southern Comets
            > and have found most around 0.2' to 0.6' off the MPC ephemeris
            > position. I have been reporting the Astrometry to the MPC (my plate
            > solution residuals are 0.2" and my post fit residuals on minor
            > planets/neo's is under 1" so I don't think it's my measurements.

            I was not talking about pre-fit residuals. Look at the posted solutions. The
            residuals are from observations within a solution - post-fit residuals.

            > These include 116P, 77p, 65p, 66P, 53p, c/2002 L9, c/2003 KV2,
            > c/2003 H2, c/2003 J1, c/2002 J4 whcih I have imaged and measured
            > over the last 2 nights.

            If your post-fit residuals residuals are good than there's no need to worry about
            your mentioned large pre-fit residuals.

            By the way, the problems with the current astrometry (especially by the surveys)
            most likely come from the very diffuse appearance which needs stacking to receive
            good results and I heard from one observer that the center itself is badly
            defined. AFAIK, the surveys do no stacking and report their positions
            automatically measured from single images. This explains nicely why LINEARs
            residuals are that bad.

            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
          • Konrad.Horn@t-online.de
            Pls. find an image fron C/2003 O2 at my homepage http://home.t-online.de/home/konrad.horn/index.htm It was realy hard to stack the images because of the
            Message 5 of 8 , Aug 2, 2003
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              Pls. find an image fron C/2003 O2 at my homepage

              http://home.t-online.de/home/konrad.horn/index.htm

              It was realy hard to stack the images because of
              the diffuse coma.

              Konrad
            • David Higgins
              Ahhhh - of course. I ll get these things sorted out in my brain one day :-) Cheers David ... plate ... solutions. The ... residuals. ... to worry about
              Message 6 of 8 , Aug 3, 2003
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                Ahhhh - of course. I'll get these things sorted out in my brain one
                day :-)

                Cheers

                David

                --- In comets-ml@yahoogroups.com, Maik Meyer <maik@c...> wrote:
                > David,
                >
                > > What do you class 'way off'? I have been imaging Southern Comets
                > > and have found most around 0.2' to 0.6' off the MPC ephemeris
                > > position. I have been reporting the Astrometry to the MPC (my
                plate
                > > solution residuals are 0.2" and my post fit residuals on minor
                > > planets/neo's is under 1" so I don't think it's my measurements.
                >
                > I was not talking about pre-fit residuals. Look at the posted
                solutions. The
                > residuals are from observations within a solution - post-fit
                residuals.
                >
                > > These include 116P, 77p, 65p, 66P, 53p, c/2002 L9, c/2003 KV2,
                > > c/2003 H2, c/2003 J1, c/2002 J4 whcih I have imaged and measured
                > > over the last 2 nights.
                >
                > If your post-fit residuals residuals are good than there's no need
                to worry about
                > your mentioned large pre-fit residuals.
              • Reiner M. Stoss
                Konrad, ... ??? Why would someone measure the centroid of the pseudo-nucleus on single frames and use this information for stacking? We do stack to get a
                Message 7 of 8 , Aug 8, 2003
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                  Konrad,

                  > Pls. find an image fron C/2003 O2 at my homepage
                  >
                  > http://home.t-online.de/home/konrad.horn/index.htm
                  >
                  > It was realy hard to stack the images because of
                  > the diffuse coma.

                  ???

                  Why would someone measure the centroid of the pseudo-nucleus
                  on single frames and use this information for stacking?
                  We do stack to get a higher SNR and thus be able to determine
                  the centroid of the pseudo-nucleus, but not the other way
                  round.

                  You have the orbit, you have the time of the images and
                  you have the reference star frame on each image.
                  This is all you need for shifting the images to get a perfect
                  stack on the comet. Astrometrica does this automatically.

                  Reiner
                  at sunny 120
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