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Re: C/2010 X1 recovery attempts.

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  • Juan José González Suárez
    Three days ago, I posted a visual observation made on the last available night without moonlight interference : C/2010 X1 (Elenin): 2011 Oct. 9.20 UT: m1=10.7,
    Message 1 of 51 , Oct 12, 2011
      Three days ago, I posted a visual observation made on the last available
      night without moonlight interference :

      C/2010 X1 (Elenin):
      2011 Oct. 9.20 UT: m1=10.7, Dia.=6', DC=1/,
      Tail: 0.2 deg. in PA 310 deg, 20 cm SCT (77x).
      [ The coma appears large and very diffuse,
      without central condensation. Observation made from
      mountain location under very good seeing conditions.
      Nearby field stars checked in DSS. Zodiacal light.
      Altitude: 23 deg.].

      At this point, it is useful to provide additional information.

      We are again speaking about one of these "problematic, extremely diluted
      and fuzzy comets" ...

      But for me this case wasn't problematic or near the threshold of
      visual detection. It was a clear observation ( the atmospheric
      conditions in the Cantabrian Mountains were near optimal down to the
      line of horizon ) made in the course of a short observing session ( 1
      hour approx. ) between moonset and the beginning of the morning
      astronomical twilight. Under such very good conditions, and besides
      C/2010 X1, my plan was to observe another four comets ( C/2010 G2,
      C/2011 S2, 49P, and 45P at low altitude ), so I only could dedicate
      approx. 10 min to the observation and magnitude estimate of C/2010 X1,
      at low magnification as necessary. I didn't check for the motion, given
      the short time-interval and the apparent lack of central condensation in
      such a large ( 6' ) coma. The geometric center of this coma was close to
      the MPC ephemeris position, with an error bar of +/- 4'.

      Best regards and clear skies,


      J. J. Gonzalez

      ( P.S.: as previously told, I don't like to discuss again on the
      diversity among CCD and visual observations ... ).


      ------------------------------------------------------------------

      Alan Watson wrote in Comet-Images :

      > Gidday all,
      > This comet is still detectable in STEREO HI2A images up to 20111009.
      > Small, more diffuse than an asteroid in this imager
      > The lower limit for this imager is about mag10-11 more in IR
      > spectrum.There should be a detectable moving diffuse object.
      > It was detected at lower mags on the way in?? May when its in a better
      > position for visual detection.
      >
      > Kind regards, Alan Watson.
    • Jakub Černý
      Hello all, I disagree with the term of erroneous observations . Observations can be done with good or bad methology. Whatever some observation does not met
      Message 51 of 51 , Oct 20, 2011
        Hello all,



        I disagree with the term of "erroneous observations". Observations can be
        done with good or bad methology. Whatever some observation does not met our
        expectation, it does not mean it is erroneous.



        I agree that 2 positive visual observations does not prove anything.



        The only conclusion in this case we may tell for sure is that there is no
        evidence yet of detection any remain of comet C/2010 X1 after solar
        conjuction.



        Best regards,

        Jakub Cerny



        From: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] On Behalf
        Of jbortle@...
        Sent: Thursday, October 20, 2011 5:10 PM
        To: comets-ml@yahoogroups.com
        Subject: Re: [comets-ml] Visual and CCD observations : (was C/2010 X1
        recovery attempts)





        I have been silent throughout this long discussion of the recent supposed
        "positive sightings" of Comet Elenin, but feel I must now speak out. I have
        watched attempts to explain why two questionable positive sightings should
        be regarded as in any way valid in the face of overwhelming negative
        evidence reported by observers with much larger instruments under as good or

        superior skies, and from deep CDD imaging. In the process the potential
        explanations have gone from the questionable to the downright absurd.

        I have been seriously observing comets longer than most here have been
        alive and can tell you that every observer, no matter what his or her
        credentials, instruments, or observing situation, including myself, is open
        to
        making occasional mistaken sightings. Through the years I have seen
        countless
        occasions where difficult objects have been reported as "seen" and
        subsequently the observations proven quite impossible. Simply put, when
        contradicted
        by many negative and better observations, it is logical to assume
        immediately that the positive sighting(s) are in error, not in need of some
        sort of
        outrageous explanations to legitimize them.

        Disintegrating comets (as opposed to splitting ones) do not survive very
        long after the process has been observed to begin, which in the case with
        Comet Elenin was all the way back in the end of August. The decline/fade of
        Elenin was abrupt and dramatic. This disintegration process historically
        does not seem to leave any long-surviving fragment(s) to continue to
        generate
        a substantial post-disruption coma. In the final stages the residual coma
        would be expected to grow ever larger and exhibit a rapidly fading surface
        brightness. Comet Elenin was less than 0.3 AU from the Earth in early
        October. If any trace at all remained of the comet's coma it should have
        subtended a very larger diameter, not 6', or so, while its surface
        brightness could
        hardly have been anticipated to be as bright as the sky background.

        Similarly, as no remnant trace of the comet could be detected when within
        the FOV of various solar monitoring satellites already back in the latter
        half of September, signaling that the comet had ceased to exist, not just
        have been growing steadily fainter day by day.

        If visual comet data is to have any lasting use to researchers in the
        future it is absolutely necessary to critically evaluation the data as it is

        currently being generated to prevent erroneous observations from entering
        the
        achieves. This should start with the observer himself, but if not the point
        should be raised by those in the observing community/archievers.
        Researchers in years to come will not be familiar with who the observers
        were, nor
        whether their observations should be taken at face value, or not, in
        situations like those surrounding a unusual cometary events. In the current
        case,
        just when Comet Elenin had fully disintegrated and dissipated would be
        critical to any analysis and potential explanation of the process. Muddying
        the waters with erroneous observations would be a great disservice to all
        concerned.

        J.Bortle






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