Re: C/2010 X1 recovery attempts.
- 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.
- 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
From: email@example.com [mailto:firstname.lastname@example.org] On Behalf
Sent: Thursday, October 20, 2011 5:10 PM
Subject: Re: [comets-ml] Visual and CCD observations : (was C/2010 X1
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
making occasional mistaken sightings. Through the years I have seen
occasions where difficult objects have been reported as "seen" and
subsequently the observations proven quite impossible. Simply put, when
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
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
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
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
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
whether their observations should be taken at face value, or not, in
situations like those surrounding a unusual cometary events. In the current
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
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