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Re: [comets-ml] Re: C/2011 L4 fading?

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  • Gerhard Dangl
    This I can confirm. Astrometrica updated with elements from the MPC showed dRA +2.8 and dDe -1.3 for all C/2011 L4 positions on my images from 2012 05 14.
    Message 1 of 18 , May 17, 2012
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      This I can confirm. Astrometrica updated with elements from the MPC
      showed dRA +2.8' and dDe -1.3' for all C/2011 L4 positions on my images
      from 2012 05 14.

      Regards
      Gerhard
      www.dangl.at


      Am 17.05.2012 13:01, schrieb terryjlovejoy:
      > Thats interesting, I've got some images from May 13 using my Hyperstar setup that shows an almost starlike object of mag 13.5! I'll have more images from tonight.
      >
      > BTW the elements currently downloaded from the Minor Planet website seem to be eroneous and give a position 3' too far east...use the ones from Horizons.
      >
      > Terry
      >
    • terryjlovejoy
      Hi Chris, The elements given in the last MPEC seem OK: http://www.minorplanetcenter.net/mpec/K12/K12J16.html Meanwhile here is some imagery from tonight:
      Message 2 of 18 , May 17, 2012
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        Hi Chris,

        The elements given in the last MPEC seem OK:

        http://www.minorplanetcenter.net/mpec/K12/K12J16.html

        Meanwhile here is some imagery from tonight:

        http://www.iceinspace.com.au/forum/showthread.php?t=90936

        http://groups.yahoo.com/group/comets-ml/files/2011L4_2012_05_17.avi

        Terry

        --- In comets-ml@yahoogroups.com, Bomber2 Panther <outbackmanyep@...> wrote:
        >
        >
        > When will the MPC fix the discrepancy? Cheers,Chris W
        > > To: comets-ml@yahoogroups.com
        > > From: ngc1976sct@...
        > > Date: Thu, 17 May 2012 04:21:48 -0700
        > > Subject: Re: [comets-ml] Re: C/2011 L4 fading?
        > >
        >
      • Soulier Jean-François
        Good morning.   C 2011 L4, 2012 05 16.98, m2=13.3 (+/- 0.1) R.O : 14.25 Echa. 2.85 /pix. Picture :
        Message 3 of 18 , May 17, 2012
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          Good morning.
           
          C 2011 L4, 2012 05 16.98, m2=13.3 (+/- 0.1)
          R.O : 14.25"
          Echa. 2.85"/pix.
          Picture : http://6888comete.free.fr/fr/imageC2011L4Panstarrsfrance.htm
           
          Sincerely.
          SOULIER Jean-François
          C10/France



          ________________________________
          De : Alan Hale <ahale@...>
          À : comets-ml@yahoogroups.com
          Envoyé le : Jeudi 17 mai 2012 9h41
          Objet : [comets-ml] C/2011 L4 fading?


           
          Hello everyone,

          From the time I first picked up this comet in late March, all through April,
          this comet seemed to be brightening slowly but steadily, maintaining the
          small, condensed coma that it initially exhibited. During my last
          observation before the recent full moon (May 2.42) I measured m1=13.8 and
          the comet was relatively easy to see, even at low magnification.

          Once the moon cleared from the evening sky we had a solid week of clouds and
          rain here. The first clear night was May 15-16, and when I looked at C/2011
          L4, I could barely detect it. I thought this might possibly be due to sky
          conditions (the air was still a bit damp), although I didn't have any
          trouble seeing any of the other faint comets that are currently visible.

          Tonight (May 17.31) the conditions are good and the air is drier, and still,
          I could only just barely detect C/2011 L4. I would charitably call it
          m1=14.2, but it also appeared considerably more diffuse than it was earlier,
          making it much more difficult to see.

          Can anyone else confirm this? Just when it looked like we northerners might
          finally have a decent comet, I'd hate to have yet another fizzle . . .

          Sincerely,

          Alan




          [Non-text portions of this message have been removed]
        • Alan Hale
          Thanks everyone for the feedback. It appears that Terry hit the issue right on the head. I was using the MPC s ephemeris service, but when I just now compared
          Message 4 of 18 , May 17, 2012
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            Thanks everyone for the feedback.

            It appears that Terry hit the issue right on the head. I was using the MPC's
            ephemeris service, but when I just now compared it to Horizons, I see that,
            indeed, MPC is giving a position some 3 arcminutes to the WNW of the
            Horizons position. It turns out that on both nights I saw "stars" very near
            the Horizons position, and while the DSS also showed faint stars near those
            locations, my "stars" appeared brighter than what the DSS seemed to
            indicate. I passed this off as being due to the fact I was using the blue
            DSS image and that the stars were probably of a spectral type that appeared
            faint in the blue.

            So [red in the face], it looks like I fell into that very trap that I've
            repeatedly warned against: I "knew" something was in a particular position,
            and saw "something" at that location. Grrrrr . . . My "star" on the first
            night even looked somewhat nonstellar and at first I thought it was the
            comet, but since it wasn't in the "correct" position I passed it off as
            being the DSS star . . .

            Hopefully I'll be able to try again tonight. Cloudy right now, but the
            forecast is calling for clear skies tonight.

            Meanwhile, I find it difficult to believe that the MPC's ephemeris service
            can be that far off . . .


            Sincerely,

            Alan
          • Alan Hale
            Hello everyone, I found the comet tonight, easily visible at the Horizons position: May 18.29, m1=13.5, 0.5 coma, DC = 8+ This whole exercise has been a
            Message 5 of 18 , May 18, 2012
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              Hello everyone,

              I found the comet tonight, easily visible at the Horizons position: May
              18.29, m1=13.5, 0.5' coma, DC = 8+

              This whole exercise has been a powerful demonstration, at least to me, of
              how expectations can color what we observe. I had clearly seen the comet the
              past two nights, but because it wasn't in the "correct" position (per the
              MPC ephemeris) I had dismissed it, and instead had manufactured an extremely
              faint "something" in the "correct" position. Of course, if the comet had
              been bright and large I would have easily figured out that something was
              wrong with the MPC ephemeris, but because the comet is faint, small, and
              almost stellar in appearance (and, moreover, is traveling through moderately
              rich star fields), I was fooled.


              Sincerely,

              Alan
            • Pieter-Jan Dekelver
              Hello everyone, I asked the Belgian group of comet observers to follow this comet also. But for us it is very low on the north horizon in the night. ... Best
              Message 6 of 18 , May 18, 2012
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                Hello everyone,



                I asked the Belgian group of comet observers to follow this comet also. But
                for us it is very low on the north horizon in the night.



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



                Best Regards,



                Mr. Pieter-Jan Dekelver

                Maasmechelen, Belgium

                pieterjan.dekelver@...

                www.astronomie.be/pieterjan.dekelver



                From: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] On Behalf
                Of Alan Hale
                Sent: donderdag 17 mei 2012 17:26
                To: comets-ml@yahoogroups.com
                Subject: Re : [comets-ml] C/2011 L4 fading?





                Thanks everyone for the feedback.

                It appears that Terry hit the issue right on the head. I was using the MPC's
                ephemeris service, but when I just now compared it to Horizons, I see that,
                indeed, MPC is giving a position some 3 arcminutes to the WNW of the
                Horizons position. It turns out that on both nights I saw "stars" very near
                the Horizons position, and while the DSS also showed faint stars near those
                locations, my "stars" appeared brighter than what the DSS seemed to
                indicate. I passed this off as being due to the fact I was using the blue
                DSS image and that the stars were probably of a spectral type that appeared
                faint in the blue.

                So [red in the face], it looks like I fell into that very trap that I've
                repeatedly warned against: I "knew" something was in a particular position,
                and saw "something" at that location. Grrrrr . . . My "star" on the first
                night even looked somewhat nonstellar and at first I thought it was the
                comet, but since it wasn't in the "correct" position I passed it off as
                being the DSS star . . .

                Hopefully I'll be able to try again tonight. Cloudy right now, but the
                forecast is calling for clear skies tonight.

                Meanwhile, I find it difficult to believe that the MPC's ephemeris service
                can be that far off . . .

                Sincerely,

                Alan





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              • gvnn64@libero.it
                Dear Mr. Pieter-Jan Dekelver. ... This comet is currently in Scorpius, and culminates due south. So, if you aim your scope south, instead of north, then you
                Message 7 of 18 , May 18, 2012
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                  Dear Mr. Pieter-Jan Dekelver.

                  > I asked the Belgian group of comet observers to follow this comet also. But
                  > for us it is very low on the north horizon in the night.

                  This comet is currently in Scorpius, and culminates due south. So, if you aim your scope south, instead of north, then you should find it a bit higher in the sky. :-)

                  Bye,
                  Giovanni
                • Pieter-Jan Dekelver
                  Whoops! My mistake! ... Best Regards, Mr. Pieter-Jan Dekelver Maasmechelen, Belgium pieterjan.dekelver@gmail.com www.astronomie.be/pieterjan.dekelver From:
                  Message 8 of 18 , May 18, 2012
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                    Whoops! My mistake!



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



                    Best Regards,



                    Mr. Pieter-Jan Dekelver

                    Maasmechelen, Belgium

                    pieterjan.dekelver@...

                    www.astronomie.be/pieterjan.dekelver



                    From: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] On Behalf
                    Of gvnn64@...
                    Sent: vrijdag 18 mei 2012 10:56
                    To: comets-ml
                    Subject: RE: [comets-ml] C/2011 L4 fading?





                    Dear Mr. Pieter-Jan Dekelver.

                    > I asked the Belgian group of comet observers to follow this comet also.
                    But
                    > for us it is very low on the north horizon in the night.

                    This comet is currently in Scorpius, and culminates due south. So, if you
                    aim your scope south, instead of north, then you should find it a bit higher
                    in the sky. :-)

                    Bye,
                    Giovanni





                    [Non-text portions of this message have been removed]
                  • gvnn64@libero.it
                    No worries, I was just kidding (we are approaching the week-end, after all). Best wishes for yours effective cometary observations. Bye, Giovanni
                    Message 9 of 18 , May 18, 2012
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                      No worries, I was just kidding (we are approaching the week-end, after all). Best wishes for yours effective cometary observations.

                      Bye,
                      Giovanni
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