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Re: [comets-ml] The full spectrum of Elenin 'news' ...

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  • kaos@kommet.cz
    Hello Dan my latest analysis gives the maximum brightnesss of comet when its, away from Sun, 6 - 7 mag, while there is still high chance that it wont even
    Message 1 of 26 , May 4, 2011
      Hello Dan

      my latest analysis gives the maximum brightnesss of comet when its, away
      from Sun, 6 - 7 mag, while there is still high chance that it wont even
      survive perihelion passage. There also exist prediction using forward
      scattering effect that may cause 7 mag higher brightness about time comet
      passing Sun, but it will he hardly visible from earth and when comet enter
      morning sky efect will almost disappear.

      Best regards,
      Jakub Cerny,
      Czech Republic

      > Oh wondrous internet, if you just look around you fill find *any* kind of
      > opinion
      > on any kind of subject, comet Elenin included - and I don't mean the
      > totally looney
      > conspiracy websites. But what about the following posting one of several
      > Elenin blogs:
      > http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-brighter-than.html
      > - here
      > it is claimed that a combination of optical effects might raise the
      > comet's apparent
      > brightness to, gasp, -20 mag.! Meanwhile on another blog L. Elenin himself
      > speaks out:
      > http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected
      > - here
      > a +4 mag. peak is foreseen. Does that match the general feeling in the
      > community?
      >
      > Dan
      >
    • gvnn64@libero.it
      Dear Dan and all. ... It s always difficult to predict the behaviour of a comet, expecially if it s a new one. What I can say for sure is that, according to
      Message 2 of 26 , May 5, 2011
        Dear Dan and all.

        > it is claimed that a combination of optical effects might raise the comet's apparent
        > brightness to, gasp, -20 mag.! Meanwhile on another blog L. Elenin himself speaks out:
        > http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected - here
        > a +4 mag. peak is foreseen. Does that match the general feeling in the community?

        It's always difficult to predict the behaviour of a comet, expecially if it's a new one.

        What I can say for sure is that, according to the last measurements of the CARA team, comet Elenin seems to have decreased somehow its activity during the past few weeks.

        As you might know, we use the afrho parameter (proxy of the dust abundance within the coma) to estimate the degree of activity of a given comet. Our data, collected in the past days, compared to the archive data gathered on the middle of March, shows a 30% decrease of the afrho parameter (on March 14 we measured 100cm, on May 02-03 this amount has dropped to about 70 cm).

        Probably we have to take into account the contribution of the phase effect, that in March probably conspired to increase the scattered light from the comet, anyway this last data is a little discouraging.

        If I might extrapolate (not an easy task right now), with this behaviour, I'm pretty skeptical about a naked eye comet next October (not to mention the -20 magn speculations).

        Hope to be wrong...

        Bye,
        Giovanni Sostero (CARA)
      • kronk@cometography.com
        I would like to point out that comet C/1995 O1 (Hale-Bopp) stopped brightening from July through September of 1996. Talk circulated that the comet was starting
        Message 3 of 26 , May 5, 2011
          I would like to point out that comet C/1995 O1 (Hale-Bopp) stopped
          brightening from July through September of 1996. Talk circulated that
          the comet was starting to fizzle. During this same three-month period,
          observatories reported the first detection of silicates (July 8), the
          first detection of methyl cyanide (August 14-17), and the first
          detection of cyanogen (August). Brightening resumed in late September
          and the comet obviously became quite bright early in 1997. Later, there
          were suggestions that fluctuations in the brightness of long-period
          comets might be normal when more than 3 AU from the sun as different
          molecules of different reflectivity began vaporizing.

          Gary

          > -------- Original Message --------
          > Subject: Re:[comets-ml] The full spectrum of Elenin 'news' ...
          > From: "gvnn64\@libero\.it" <gvnn64@...>
          > Date: Thu, May 05, 2011 3:14 am
          > To: "comets-ml" <comets-ml@yahoogroups.com>
          >
          >
          > Dear Dan and all.
          >
          > > it is claimed that a combination of optical effects might raise the comet's apparent
          > > brightness to, gasp, -20 mag.! Meanwhile on another blog L. Elenin himself speaks out:
          > > http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected - here
          > > a +4 mag. peak is foreseen. Does that match the general feeling in the community?
          >
          > It's always difficult to predict the behaviour of a comet, expecially if it's a new one.
          >
          > What I can say for sure is that, according to the last measurements of the CARA team, comet Elenin seems to have decreased somehow its activity during the past few weeks.
          >
          > As you might know, we use the afrho parameter (proxy of the dust abundance within the coma) to estimate the degree of activity of a given comet. Our data, collected in the past days, compared to the archive data gathered on the middle of March, shows a 30% decrease of the afrho parameter (on March 14 we measured 100cm, on May 02-03 this amount has dropped to about 70 cm).
          >
          > Probably we have to take into account the contribution of the phase effect, that in March probably conspired to increase the scattered light from the comet, anyway this last data is a little discouraging.
          >
          > If I might extrapolate (not an easy task right now), with this behaviour, I'm pretty skeptical about a naked eye comet next October (not to mention the -20 magn speculations).
          >
          > Hope to be wrong...
          >
          > Bye,
          > Giovanni Sostero (CARA)
        • Jakub Černý
          Hello Gary and all, I would also note similarity to comet C/1999 S4 (LINEAR) which also experienced many small outburst and fades before it finally
          Message 4 of 26 , May 5, 2011
            Hello Gary and all,



            I would also note similarity to comet C/1999 S4 (LINEAR) which also experienced many small outburst and fades before it finally disintegrate at perihelium. As far as I know comet Elenin is first time Sun visitor from Oort cloud, according to its actual activity, we may expect it is very smal body (maybe between 100 – 500 m diameter) with very big active surface fraction. High volume of volatiles may cause strong eruption activity that tears its surface. I think if comet will continue with so unstable photometric parameters, it can increase posibility that we can see another comet disintegration.



            Best regards,

            Jakub Cerny

            Czech Republic



            From: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] On Behalf Of kronk@...
            Sent: Thursday, May 05, 2011 7:15 PM
            To: comets-ml@yahoogroups.com
            Subject: RE: [comets-ml] The full spectrum of Elenin 'news' ...





            I would like to point out that comet C/1995 O1 (Hale-Bopp) stopped
            brightening from July through September of 1996. Talk circulated that
            the comet was starting to fizzle. During this same three-month period,
            observatories reported the first detection of silicates (July 8), the
            first detection of methyl cyanide (August 14-17), and the first
            detection of cyanogen (August). Brightening resumed in late September
            and the comet obviously became quite bright early in 1997. Later, there
            were suggestions that fluctuations in the brightness of long-period
            comets might be normal when more than 3 AU from the sun as different
            molecules of different reflectivity began vaporizing.

            Gary

            > -------- Original Message --------
            > Subject: Re:[comets-ml] The full spectrum of Elenin 'news' ...
            > From: "gvnn64\@libero\.it" <gvnn64@... <mailto:gvnn64%40libero.it> >
            > Date: Thu, May 05, 2011 3:14 am
            > To: "comets-ml" <comets-ml@yahoogroups.com <mailto:comets-ml%40yahoogroups.com> >
            >
            >
            > Dear Dan and all.
            >
            > > it is claimed that a combination of optical effects might raise the comet's apparent
            > > brightness to, gasp, -20 mag.! Meanwhile on another blog L. Elenin himself speaks out:
            > > http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected - here
            > > a +4 mag. peak is foreseen. Does that match the general feeling in the community?
            >
            > It's always difficult to predict the behaviour of a comet, expecially if it's a new one.
            >
            > What I can say for sure is that, according to the last measurements of the CARA team, comet Elenin seems to have decreased somehow its activity during the past few weeks.
            >
            > As you might know, we use the afrho parameter (proxy of the dust abundance within the coma) to estimate the degree of activity of a given comet. Our data, collected in the past days, compared to the archive data gathered on the middle of March, shows a 30% decrease of the afrho parameter (on March 14 we measured 100cm, on May 02-03 this amount has dropped to about 70 cm).
            >
            > Probably we have to take into account the contribution of the phase effect, that in March probably conspired to increase the scattered light from the comet, anyway this last data is a little discouraging.
            >
            > If I might extrapolate (not an easy task right now), with this behaviour, I'm pretty skeptical about a naked eye comet next October (not to mention the -20 magn speculations).
            >
            > Hope to be wrong...
            >
            > Bye,
            > Giovanni Sostero (CARA)





            [Non-text portions of this message have been removed]
          • Alan Hale
            Hi Gary, and all, ... I remember this incident well, for obvious reasons. I tend to agree with the point that I think Gary is trying to make, i.e., it is still
            Message 5 of 26 , May 5, 2011
              Hi Gary, and all,

              >
              > I would like to point out that comet C/1995 O1 (Hale-Bopp) stopped
              > brightening from July through September of 1996. Talk circulated that
              > the comet was starting to fizzle. During this same three-month period,
              > observatories reported the first detection of silicates (July 8), the
              > first detection of methyl cyanide (August 14-17), and the first
              > detection of cyanogen (August). Brightening resumed in late September
              > and the comet obviously became quite bright early in 1997. Later, there
              > were suggestions that fluctuations in the brightness of long-period
              > comets might be normal when more than 3 AU from the sun as different
              > molecules of different reflectivity began vaporizing.
              >

              I remember this incident well, for obvious reasons.

              I tend to agree with the point that I think Gary is trying to make, i.e., it
              is still somewhat premature to state that Comet Elenin will do this or will
              not do that, etc. -- we're going to have to wait to see what the comet
              actually does. David Levy's comparison between comets and cats, and Fred
              Whipple's axiom about betting on horses vs. comets, would seem to apply
              here.

              That being said, the potential for a decent display from Comet Elenin
              certainly exists, although I'm not holding my breath for any "Great Comet"
              display. I would consider it pretty reckless to make any predictions along
              those lines -- for example, the "magnitude -20" prediction that Dan Fischer
              cited as an example at the beginning of this thread. (It would be nice,
              certainly, but as the tag line in that series of commercials goes, "get
              real!")


              Sincerely,

              Alan
            • P. Edward Murray
              Why worry? The comet will do whatever it wants to do and when it wants to do it:) Just enjoy the show! Ed Murray ... From: Jakub Černý To:
              Message 6 of 26 , May 5, 2011
                Why worry?

                The comet will do whatever it "wants" to do and when it "wants" to do it:)

                Just enjoy the show!

                Ed Murray
                ----- Original Message -----
                From: Jakub Černý
                To: comets-ml@yahoogroups.com
                Sent: Thursday, May 05, 2011 2:13 PM
                Subject: RE: [comets-ml] The full spectrum of Elenin 'news' ...



                Hello Gary and all,

                I would also note similarity to comet C/1999 S4 (LINEAR) which also experienced many small outburst and fades before it finally disintegrate at perihelium. As far as I know comet Elenin is first time Sun visitor from Oort cloud, according to its actual activity, we may expect it is very smal body (maybe between 100 – 500 m diameter) with very big active surface fraction. High volume of volatiles may cause strong eruption activity that tears its surface. I think if comet will continue with so unstable photometric parameters, it can increase posibility that we can see another comet disintegration.

                Best regards,

                Jakub Cerny

                Czech Republic

                From: comets-ml@yahoogroups.com [mailto:comets-


                [Non-text portions of this message have been removed]
              • gvnn64@libero.it
                Dears Gary and Jakub (and all), the two comets you choose as potential comparisons with comet Elenin s behaviour -C/1999 S4 (LINEAR) and C/1995 O1 (Hale-Bopp)-
                Message 7 of 26 , May 6, 2011
                  Dears Gary and Jakub (and all),
                  the two comets you choose as potential comparisons with comet Elenin's behaviour -C/1999 S4 (LINEAR) and C/1995 O1 (Hale-Bopp)- are, for different reasons, two of the most unusual objects available on the cometary market! Probably each and every comet has its own peculiarities, however these two are really "3-sigma" off the standard deviation of the cometary bestiary (pretty rich of exceptions for itsef).

                  > I would like to point out that comet C/1995 O1 (Hale-Bopp) stopped
                  > brightening from July through September of 1996. Talk circulated that
                  > the comet was starting to fizzle.
                  <snip>
                  >Brightening resumed in late September
                  > and the comet obviously became quite bright early in 1997.

                  Gary, personally I really hope that this will be also the case of comet Elenin. However... in my previus email, I didn't commented about a simple brightness decrese or fluctuation on C/2010 X1 (from an m1 and m2 point of view, actually the comet continues to get bright) but, instead, about an afrho decrease. This is a subtle but foundamental distinction since, if it is true, what we are witnessing might be a change in the comet's activity, in particular that connected with the dust abundance within the coma. And, finally, if this will be actually the case, then what we might see is (possibly) a change in the comet's pace.
                  In other words, continuing with the example of comet Hale-Bopp you suggested initially, you can see from the published papers (e.g. see pg. 317 in this article: http://tinyurl.com/62lfvfx) that while the fluctuations in the apparent brightness of the comet you mentioned were happening, the afrho parameter actually had a nearly constat trend. Incidentally, also for this reason the astronomers frequently prefer to talk about the afrho parameter, instead of the apparent brightness -i.e. m1- when dealing with cometary activity...

                  > I would also note similarity to comet C/1999 S4 (LINEAR) which also experienced many small outburst and fades before it finally disintegrate at perihelium. As far as I know comet Elenin is first time Sun visitor from Oort cloud, according to its actual activity, we may expect it is very smal body (maybe between 100 - 500 m diameter) with very big active surface fraction. <snip>

                  Jakub, frankly speaking I cannot see in current's C/2010 X1 lightcurve any of the "small outburst and fades" you mentioned. Probably there was a phase effect (about the middle of March) that shows up in the ccd photometry, however this should not ne confusd with an "outburst" (intended as a momentary spike in the comet's activity); probably it was just a "gentle" photometric effect due to the change of our line of sight along the comet. About your speculations on comet Elenin's nuclear physical size and properties, well... uhm, I think that you made a number of assumptions (and we do know so little about the actual physical parameters of comets, in particular for those having eccentricity about 1 as comet Elenin).

                  Well, after all, the simple comment of Ed might be a wise suggestion.

                  Bye,
                  Giovanni
                • Ellen Papenburg
                  coming out of lurking mode... Dear Ed, With all due respect... Sure all of us will enjoy the show .. but is this not about finding out the REASONs for a
                  Message 8 of 26 , May 6, 2011
                    coming out of lurking mode...

                    Dear Ed,

                    With all due respect...

                    Sure all of us will enjoy the "show".. but is this not about finding out the REASONs for a comet's behaviour?

                    If it is just for the "show", I can watch only SciFi (do that anyways) instead of looking at the real thing and contributing to observations so we can try to understand. That is what science is about.

                    Happy clear skies :-)

                    Ellen, Ontario, Canada

                    ----- Original Message -----

                    Posted by: "P. Edward Murray"ed1ward2@... eddiestardust
                    Date: Thu May 5, 2011 11:46 am ((PDT))

                    Why worry?

                    The comet will do whatever it "wants" to do and when it "wants" to do it:)

                    Just enjoy the show!

                    Ed Murray

                    From: Jakub Černý
                    To:comets-ml@yahoogroups.com
                    Sent: Thursday, May 05, 2011 2:13 PM
                    Subject: RE: [comets-ml] The full spectrum of Elenin 'news' ...



                    Hello Gary and all,

                    I would also note similarity to comet C/1999 S4 (LINEAR) which also experienced many small outburst and fades before it finally disintegrate at perihelium. As far as I know comet Elenin is first time Sun visitor from Oort cloud, according to its actual activity, we may expect it is very smal body (maybe between 100 – 500 m diameter) with very big active surface fraction. High volume of volatiles may cause strong eruption activity that tears its surface. I think if comet will continue with so unstable photometric parameters, it can increase posibility that we can see another comet disintegration.

                    Best regards,

                    Jakub Cerny

                    Czech Republic

                    From:comets-ml@yahoogroups.com [mailto:comets-
                  • Jakub Černý
                    Hi Giovanni and all, I disagree that comet C/1999 S4 was unusal, we already experienced many total disintegrations of comets and the story of comet LINEAR was
                    Message 9 of 26 , May 6, 2011
                      Hi Giovanni and all,



                      I disagree that comet C/1999 S4 was unusal, we already experienced many
                      total disintegrations of comets and the story of comet LINEAR was exception
                      in case it was in very good position on sky and was deeply investigated by
                      HST from where we see the original body had about 200m diameter. Many of
                      theese disintegrating microcomets are not even noticed because they
                      disappear at unobservable location, for example last year comet McNaught
                      disappeared while conjuction with Sun.



                      When I look over some of theese comets in past which I can remember I can
                      see many similarities:




                      Comet

                      m0

                      n

                      orig 1/a

                      q

                      Original period


                      C/1996 Q1 (Tabur)

                      6,6

                      6,0

                      0,0019533

                      0,839811

                      11 584


                      C/1997 N1 ( Tabur )

                      10,5

                      4,0

                      -0,0001202

                      0,395626

                      Hyperbolic


                      C/1999 S4 ( LINEAR )

                      8,3

                      3,2

                      0,0000029

                      0,765138

                      202 489 731


                      C/2002 O4 ( Hoenig )

                      7,0

                      10,0

                      -0,000786

                      0,776203

                      Hyperbolic


                      C/2009 O2 ( Catalina )

                      10,0

                      4,6

                      0,000325

                      0,695454

                      170 677


                      ??? C/2009 R1 ( McNaught )

                      6,5

                      4,8

                      0,000013

                      0,405026

                      21 334 623


                      C/2010 X1 (Elenin)

                      10,0

                      2,5

                      0,000011

                      0,482457

                      27 410 122



                      When you look at the table of disintegrated small comets you can see common
                      signs:

                      - They are dynamically new comets from oort cloud

                      - They have perihelium inside Earth orbit

                      - Their inicial absolute magnitude before disintegration began is
                      less then 6,5 mag (depends on perihelion distance, more active, probably
                      larger comets need to go closer)



                      Of course we dont know much about physical characteristics of dynamically
                      new comets, but we can expect that subjective high activity of theese comets
                      against periodic ones come from much larger active fraction of nucleus. Thus
                      most of dynamically new comets with such inicial magnitude parameters and
                      perhelium inside Earth orbit are going to disintegrate, while we are able to
                      catch it only for comets that are observable long time around perihelion.



                      For comet Elenin I just trying to say that most optimistic scenario such as
                      Naked Eye visibility have low probability.



                      When i examine observations there are two fluctuations in comet magnitude
                      evolution http://www.kommet.cz/datas/users/lightcurve_20110506-145248_1.png
                      first change occured at March on CCD, second was noticed by visual observers
                      past week while comet noticeably brightened over few days for more then 0,5
                      mag. From this data is hard to say what actually going on, there is too few
                      on it, but I can say, that magnitude evolution of this comet is not calm.



                      Best regards and clear skies!

                      Jakub Cerny,

                      Czech Republic







                      From: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] On Behalf
                      Of gvnn64@...
                      Sent: Friday, May 06, 2011 11:09 AM
                      To: comets-ml
                      Subject: RE: [comets-ml] The full spectrum of Elenin 'news' ...





                      Dears Gary and Jakub (and all),
                      the two comets you choose as potential comparisons with comet Elenin's
                      behaviour -C/1999 S4 (LINEAR) and C/1995 O1 (Hale-Bopp)- are, for different
                      reasons, two of the most unusual objects available on the cometary market!
                      Probably each and every comet has its own peculiarities, however these two
                      are really "3-sigma" off the standard deviation of the cometary bestiary
                      (pretty rich of exceptions for itsef).

                      > I would like to point out that comet C/1995 O1 (Hale-Bopp) stopped
                      > brightening from July through September of 1996. Talk circulated that
                      > the comet was starting to fizzle.
                      <snip>
                      >Brightening resumed in late September
                      > and the comet obviously became quite bright early in 1997.

                      Gary, personally I really hope that this will be also the case of comet
                      Elenin. However... in my previus email, I didn't commented about a simple
                      brightness decrese or fluctuation on C/2010 X1 (from an m1 and m2 point of
                      view, actually the comet continues to get bright) but, instead, about an
                      afrho decrease. This is a subtle but foundamental distinction since, if it
                      is true, what we are witnessing might be a change in the comet's activity,
                      in particular that connected with the dust abundance within the coma. And,
                      finally, if this will be actually the case, then what we might see is
                      (possibly) a change in the comet's pace.
                      In other words, continuing with the example of comet Hale-Bopp you suggested
                      initially, you can see from the published papers (e.g. see pg. 317 in this
                      article: http://tinyurl.com/62lfvfx) that while the fluctuations in the
                      apparent brightness of the comet you mentioned were happening, the afrho
                      parameter actually had a nearly constat trend. Incidentally, also for this
                      reason the astronomers frequently prefer to talk about the afrho parameter,
                      instead of the apparent brightness -i.e. m1- when dealing with cometary
                      activity...

                      > I would also note similarity to comet C/1999 S4 (LINEAR) which also
                      experienced many small outburst and fades before it finally disintegrate at
                      perihelium. As far as I know comet Elenin is first time Sun visitor from
                      Oort cloud, according to its actual activity, we may expect it is very smal
                      body (maybe between 100 - 500 m diameter) with very big active surface
                      fraction. <snip>

                      Jakub, frankly speaking I cannot see in current's C/2010 X1 lightcurve any
                      of the "small outburst and fades" you mentioned. Probably there was a phase
                      effect (about the middle of March) that shows up in the ccd photometry,
                      however this should not ne confusd with an "outburst" (intended as a
                      momentary spike in the comet's activity); probably it was just a "gentle"
                      photometric effect due to the change of our line of sight along the comet.
                      About your speculations on comet Elenin's nuclear physical size and
                      properties, well... uhm, I think that you made a number of assumptions (and
                      we do know so little about the actual physical parameters of comets, in
                      particular for those having eccentricity about 1 as comet Elenin).

                      Well, after all, the simple comment of Ed might be a wise suggestion.

                      Bye,
                      Giovanni





                      [Non-text portions of this message have been removed]
                    • gvnn64@libero.it
                      Dear Jakun, thanks for yours comments. I will not go into the technical discussion about fragmenting comets, since my personal opinion is that we do not have
                      Message 10 of 26 , May 6, 2011
                        Dear Jakun,
                        thanks for yours comments.

                        I will not go into the technical discussion about fragmenting comets, since my personal opinion is that we do not have enough statistics to draw any conclusion about it, not to mention the forecast about potential disrupting comets (except some sungrazing objects, for sure). I want just to point out that, from time to time, some folks in this list are popping-up, announcing the disrupion of a given comet on its way to perihelion. There was several instances about this, including the memorable example of C/2006 P1 (McNaught), that hopefully was a shining example of the contrary. Statistically, from time to time, someone might win the bet, for sure. ;-)

                        Well, I understand that about this topic we have different opinions, but it is just fine in this way (it's nice to talk about this matters, anyway).

                        > For comet Elenin I just trying to say that most optimistic scenario such as
                        > Naked Eye visibility have low probability.

                        OK, I buy it.

                        > When i examine observations there are two fluctuations in comet magnitude
                        > evolution http://www.kommet.cz/datas/users/lightcurve_20110506-145248_1.png
                        > first change occured at March on CCD

                        And this was the phase effect I was talking about.

                        > second was noticed by visual observers

                        Oh my... but... we do have just a few visual observers that are reporting it, while others (not dummies: trusty observers as well) are not seeing it at all! Oh well, indeed this might be taken as a "fluctuation" in the lightcurve, but probably not in the common sense we deserve to this word... :-)

                        > past week while comet noticeably brightened over few days for more then 0,5
                        > mag. From this data is hard to say what actually going on, there is too few
                        > on it, but I can say, that magnitude evolution of this comet is not calm.

                        I see the data scattering you mentioned, however we must take into consideration several factors associated with those measurements, like:
                        1) which are the error bars of these data points?
                        2) in which way were they obtained?
                        3) did you measured different apertures for the coma?
                        etc.

                        I would not be surprised that a data *scattering* of several tenths, to even one full magnitude, might be possible for unfiltered CCD measurements of comet Elenin at this stage. Then, I suspect that any consideration about half a magnitude fluction on few scattered data points, is a little dangerous, right now.

                        IMHO, under this circumstances it's pretty hard to discuss about "brightness fluctuations" of the comet, and to get toward any conclusion about its (potential) catastrophic future. For sure, the comet might frizzle in a few months, but not based on the current observations evidences, I think...

                        Bye,
                        Giovanni
                      • P. Edward Murray
                        Ellen, I just don t think there is enough data to say with any certainty and we don t have, as yet, any spacecraft looking at it from close quarters or even a
                        Message 11 of 26 , May 6, 2011
                          Ellen,

                          I just don't think there is enough data to say with any certainty and we don't have, as yet, any spacecraft looking at it from close quarters or even a scientific package on the surface.

                          Yes, by all means continue to observe and record but the comet will do whatever it will do ....with or without our acceptance:)

                          Ed Murray
                          ----- Original Message -----
                          From: Ellen Papenburg
                          To: comets-ml@yahoogroups.com
                          Sent: Friday, May 06, 2011 10:29 AM
                          Subject: Re: [comets-ml] Re: The full spectrum of Elenin 'news' ...



                          coming out of lurking mode...

                          Dear Ed,

                          With all due respect...

                          Sure all of us will enjoy the "show".. but is this not about finding out the REASONs for a comet's behaviour?

                          If it is just for the "show", I can watch only SciFi (do that anyways) instead of looking at the real thing and contributing to observations so we can try to understand. That is what science is about.

                          Happy clear skies :-)

                          Ellen, Ontario, Canada

                          ----- Original Message -----

                          Posted by: "P. Edward Murray"ed1ward2@... eddiestardust
                          Date: Thu May 5, 2011 11:46 am ((PDT))

                          Why worry?

                          The comet will do whatever it "wants" to do and when it "wants" to do it:)

                          Just enjoy the show!

                          Ed Murray

                          From: Jakub Černý
                          To:comets-ml@yahoogroups.com
                          Sent: Thursday, May 05, 2011 2:13 PM
                          Subject: RE: [comets-ml] The full spectrum of Elenin 'news' ...

                          Hello Gary and all,

                          I would also note similarity to comet C/1999 S4 (LINEAR) which also experienced many small outburst and fades before it finally disintegrate at perihelium. As far as I know comet Elenin is first time Sun visitor from Oort cloud, according to its actual activity, we may expect it is very smal body (maybe between 100 – 500 m diameter) with very big active surface fraction. High volume of volatiles may cause strong eruption activity that tears its surface. I think if comet will continue with so unstable photometric parameters, it can increase posibility that we can see another comet disintegration.

                          Best regards,

                          Jakub Cerny

                          Czech Republic

                          From:comets-ml@yahoogroups.com [mailto:comets-





                          [Non-text portions of this message have been removed]
                        • Jakub Černý
                          Dear Giovanni and all, Yes withcomets it is always a roulette J. The best we have at this moment is empiric formula of John Bortle ( Post-Perihelion survival
                          Message 12 of 26 , May 6, 2011
                            Dear Giovanni and all,



                            Yes withcomets it is always a roulette J. The best we have at this moment is
                            empiric formula of John Bortle ( " Post-Perihelion survival of comets with
                            small q ", ICQ Vol. 13, No. 3 - Whole Number 79, July 1991, pp. 89-91. )
                            which giving value H10 = 9.89 mag in case of comet Elenin, actually its
                            absolute magnitude is near 10 mag.



                            For example same formula give for comet C/2006 P1 (McNaught) gave value H10
                            = 8.02 mag while its absolute mag shortly before perihelion passage was 6
                            mag (with similar "n" parameter as its calculated for Elenin), so comet was
                            "safe".



                            From my experience with photometric behaviours of long periodic comets there
                            are subclass with photometric behavious typical for short periodic comets
                            instead of dynamicaly new comets, for theese comets later is usually
                            calculated orbit with period of houndreds or few milion years which is still
                            astronomically short time. Some of theese comets could visit Sun already
                            tens or even thousand times and that can explain this behaviour. If you find
                            long period comet like this, simillar to periodic comets, it brighten when
                            they are closer to Sun and later their absolute magnitude get higher. I
                            believe that for comet Elenin is orbit well calculated to extrude this
                            possibility.



                            About the fluctuation of visual magnitude, I saw the report of increase in
                            brightness that is faster then expected from two experienced visual
                            observers (J.S. Gonzales and J.Koukal) and my latest visual observation
                            confirms the trend anyway I am not trying to do any conclusion from it, time
                            will show J



                            While observing comet C/1999 S4 (LINEAR) there was several microutbursts
                            which caused brighter condensation but almost had no efect on total
                            magnitude. But there was recorded few changes in water production rate from
                            radio observatories.



                            My tip is that comet Elenin won't be calm, and it will disappoint many
                            people!

                            In other hand if it will really disintegrate, we may have very good chance
                            for studying debris when passing close to Earth and it can tell us something
                            more about comets especially dynamically new one J



                            Best regards and clear skies!

                            Jakub Cerny

                            Czech Republic



                            From: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] On Behalf
                            Of gvnn64@...
                            Sent: Friday, May 06, 2011 6:00 PM
                            To: comets-ml
                            Subject: RE: [comets-ml] The full spectrum of Elenin 'news' ...





                            Dear Jakun,
                            thanks for yours comments.

                            I will not go into the technical discussion about fragmenting comets, since
                            my personal opinion is that we do not have enough statistics to draw any
                            conclusion about it, not to mention the forecast about potential disrupting
                            comets (except some sungrazing objects, for sure). I want just to point out
                            that, from time to time, some folks in this list are popping-up, announcing
                            the disrupion of a given comet on its way to perihelion. There was several
                            instances about this, including the memorable example of C/2006 P1
                            (McNaught), that hopefully was a shining example of the contrary.
                            Statistically, from time to time, someone might win the bet, for sure. ;-)

                            Well, I understand that about this topic we have different opinions, but it
                            is just fine in this way (it's nice to talk about this matters, anyway).

                            > For comet Elenin I just trying to say that most optimistic scenario such
                            as
                            > Naked Eye visibility have low probability.

                            OK, I buy it.

                            > When i examine observations there are two fluctuations in comet magnitude
                            > evolution
                            http://www.kommet.cz/datas/users/lightcurve_20110506-145248_1.png
                            > first change occured at March on CCD

                            And this was the phase effect I was talking about.

                            > second was noticed by visual observers

                            Oh my... but... we do have just a few visual observers that are reporting
                            it, while others (not dummies: trusty observers as well) are not seeing it
                            at all! Oh well, indeed this might be taken as a "fluctuation" in the
                            lightcurve, but probably not in the common sense we deserve to this word...
                            :-)

                            > past week while comet noticeably brightened over few days for more then
                            0,5
                            > mag. From this data is hard to say what actually going on, there is too
                            few
                            > on it, but I can say, that magnitude evolution of this comet is not calm.

                            I see the data scattering you mentioned, however we must take into
                            consideration several factors associated with those measurements, like:
                            1) which are the error bars of these data points?
                            2) in which way were they obtained?
                            3) did you measured different apertures for the coma?
                            etc.

                            I would not be surprised that a data *scattering* of several tenths, to even
                            one full magnitude, might be possible for unfiltered CCD measurements of
                            comet Elenin at this stage. Then, I suspect that any consideration about
                            half a magnitude fluction on few scattered data points, is a little
                            dangerous, right now.

                            IMHO, under this circumstances it's pretty hard to discuss about "brightness
                            fluctuations" of the comet, and to get toward any conclusion about its
                            (potential) catastrophic future. For sure, the comet might frizzle in a few
                            months, but not based on the current observations evidences, I think...

                            Bye,
                            Giovanni





                            [Non-text portions of this message have been removed]
                          • Juan José González Suárez
                            Dear Giovanni, I don t want to enter in any kind of debate concerning C/2010 X1, and especially with you, a valued old friend. [ and quoting again your words,
                            Message 13 of 26 , May 6, 2011
                              Dear Giovanni,

                              I don't want to enter in any kind of debate concerning C/2010 X1,
                              and especially with you, a valued old friend.

                              [ and quoting again your words, "... we are used to find such diversity
                              among CCD measurements and visual estimations of comets ( we discussed a
                              lot about this topic in the past, and I don't like to rise again such
                              boring discussion ) ..." ].

                              So, only two comments :

                              First : After the initial thread ( "C/2010 X1 (Elenin) visually
                              observable at m1=14.9" ) related to C/2010 X1 visual estimates, Bernd
                              Hausler called my attention to an interesting previous estimate of the
                              comet made by an experienced german observer, Walter Kutschera, on March
                              28.95 UT : m1=14.6 :

                              2010X1 2011 03 28.95 S 14.6 HS 92.0L 4 125 0.8 3
                              KUT 5.8 elongiert

                              ( http://kometen.fg-vds.de/obsaktinh.htm , ICQ Format )

                              In any case, you are correct : just a few visual observers were
                              reporting it, while others ( trusted observers as well ) were not seeing
                              it at all ...

                              Second : You wrote : " Incidentally, also for this reason the
                              astronomers frequently prefer to talk about the afrho parameter, instead
                              of the apparent brightness - i.e. m1- when dealing with cometary
                              activity..."

                              You are also correct in this statement ...

                              A possible conclusion ? Well ... Reading some of your words ( and
                              some other older posts in this list ) ... If only CCD photometry rules,
                              and m1 estimates are sometimes judged to be without value for any good
                              cometary work ... maybe the "old-style" visual observers like me ( I am
                              near 60 now ) must retire from seeking the best dark mountain skies,
                              travelling thousands of kilometers on rugged roads, and finally come
                              back home to a ( well deserved ) rest ...

                              ( Maybe I'm only making some kind of "semi-realistic" reflection,
                              but it could be true ... )

                              Thanks in any case, Giovanni, for your inquisitive input. Best wishes
                              and clear skies,


                              J. J. Gonzalez


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

                              Giovanni Sostero wrote :

                              > Dear Jakub,
                              > thanks for yours comments.
                              >
                              > ...
                              >
                              >> second was noticed by visual observers
                              >>
                              >
                              > Oh my... but... we do have just a few visual observers that are reporting it, while others (not dummies: trusty observers as well) are not seeing it at all! Oh well, indeed this might be taken as a "fluctuation" in the lightcurve, but probably not in the common sense we deserve to this word... :-)
                              >

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

                              Sostero wrote :

                              > Dears Gary and Jakub (and all),
                              > the two comets you choose as potential comparisons with comet Elenin's behaviour -C/1999 S4 (LINEAR) and C/1995 O1 (Hale-Bopp)- are, for different reasons, two of the most unusual objects available on the cometary market! Probably each and every comet has its own peculiarities, however these two are really "3-sigma" off the standard deviation of the cometary bestiary (pretty rich of exceptions for itsef).
                              >
                              > ...
                              > In other words, continuing with the example of comet Hale-Bopp you suggested initially, you can see from the published papers (e.g. see pg. 317 in this article: http://tinyurl.com/62lfvfx) that while the fluctuations in the apparent brightness of the comet you mentioned were happening, the afrho parameter actually had a nearly constat trend. Incidentally, also for this reason the astronomers frequently prefer to talk about the afrho parameter, instead of the apparent brightness -i.e. m1- when dealing with cometary activity...
                              >
                              > Bye,
                              > Giovanni
                              >
                              -----------------------------------------------------------------

                              Sostero wrote ( Apr. 6 ) :

                              > Hello John,
                              > thanks for yours comments.
                              >
                              >
                              >> Perhaps a word of caution is advisable here.
                              >>
                              >
                              > The point I raised is obviously based on the reliability of the visual estimations we have seen so far. If there is any doubt about the consistency of this data, well then question drops.
                              >
                              > In the past I made just a few visual estimation of comets myself, so for this I mainly rely on the experience of trusted observers (as you and Juan).
                              >
                              > Bye,
                              > Giovanni
                              >
                            • gvnn64
                              Dears Jakub and Juan, thanks for yours reply. I comment here only about the secon point raised by J:J. (value of visual estimates of comers). I think that
                              Message 14 of 26 , May 6, 2011
                                Dears Jakub and Juan,
                                thanks for yours reply.

                                I comment here only about the secon point raised by J:J. (value of visual estimates of comers). I think that there was a misunderstading here: it was not my intention to say that visual observations are useless. What I wanted to say was, instead, that for *physical* considerations about comet's behaviour, the professionals prefer to deal with other parameters (like the afrho quantity). This is pretty clear browsing through the scientific literature.
                                IMHO visual estimates of comets are still pretty interesting and important (e.g. For a first estimate of a given comet's behaviour). Apart of this, as an amateur, I consider that the work that you, and others, are performing regularly on many comets, is of the uppermost importance, and a pleasure for itself (I always feel a form of envy, reading about yours expeditions under dark, mountain skies).
                                Hope that you will continue this activity well over your eighties.

                                Bye,
                                Giovanni







                                --- In comets-ml@yahoogrou

                                ps.com, Juan José González Suárez <jjgonzalez@...> wrote:
                                >
                                > Dear Giovanni,
                                >
                                > I don't want to enter in any kind of debate concerning C/2010 X1,
                                > and especially with you, a valued old friend.
                                >
                                > [ and quoting again your words, "... we are used to find such diversity
                                > among CCD measurements and visual estimations of comets ( we discussed a
                                > lot about this topic in the past, and I don't like to rise again such
                                > boring discussion ) ..." ].
                                >
                                > So, only two comments :
                                >
                                > First : After the initial thread ( "C/2010 X1 (Elenin) visually
                                > observable at m1=14.9" ) related to C/2010 X1 visual estimates, Bernd
                                > Hausler called my attention to an interesting previous estimate of the
                                > comet made by an experienced german observer, Walter Kutschera, on March
                                > 28.95 UT : m1=14.6 :
                                >
                                > 2010X1 2011 03 28.95 S 14.6 HS 92.0L 4 125 0.8 3
                                > KUT 5.8 elongiert
                                >
                                > ( http://kometen.fg-vds.de/obsaktinh.htm , ICQ Format )
                                >
                                > In any case, you are correct : just a few visual observers were
                                > reporting it, while others ( trusted observers as well ) were not seeing
                                > it at all ...
                                >
                                > Second : You wrote : " Incidentally, also for this reason the
                                > astronomers frequently prefer to talk about the afrho parameter, instead
                                > of the apparent brightness - i.e. m1- when dealing with cometary
                                > activity..."
                                >
                                > You are also correct in this statement ...
                                >
                                > A possible conclusion ? Well ... Reading some of your words ( and
                                > some other older posts in this list ) ... If only CCD photometry rules,
                                > and m1 estimates are sometimes judged to be without value for any good
                                > cometary work ... maybe the "old-style" visual observers like me ( I am
                                > near 60 now ) must retire from seeking the best dark mountain skies,
                                > travelling thousands of kilometers on rugged roads, and finally come
                                > back home to a ( well deserved ) rest ...
                                >
                                > ( Maybe I'm only making some kind of "semi-realistic" reflection,
                                > but it could be true ... )
                                >
                                > Thanks in any case, Giovanni, for your inquisitive input. Best wishes
                                > and clear skies,
                                >
                                >
                                > J. J. Gonzalez
                                >
                                >
                                > ---------------------------------------------------------------------
                                >
                                > Giovanni Sostero wrote :
                                >
                                > > Dear Jakub,
                                > > thanks for yours comments.
                                > >
                                > > ...
                                > >
                                > >> second was noticed by visual observers
                                > >>
                                > >
                                > > Oh my... but... we do have just a few visual observers that are reporting it, while others (not dummies: trusty observers as well) are not seeing it at all! Oh well, indeed this might be taken as a "fluctuation" in the lightcurve, but probably not in the common sense we deserve to this word... :-)
                                > >
                                >
                                > --------------------------------------------------------------------
                                >
                                > Sostero wrote :
                                >
                                > > Dears Gary and Jakub (and all),
                                > > the two comets you choose as potential comparisons with comet Elenin's behaviour -C/1999 S4 (LINEAR) and C/1995 O1 (Hale-Bopp)- are, for different reasons, two of the most unusual objects available on the cometary market! Probably each and every comet has its own peculiarities, however these two are really "3-sigma" off the standard deviation of the cometary bestiary (pretty rich of exceptions for itsef).
                                > >
                                > > ...
                                > > In other words, continuing with the example of comet Hale-Bopp you suggested initially, you can see from the published papers (e.g. see pg. 317 in this article: http://tinyurl.com/62lfvfx) that while the fluctuations in the apparent brightness of the comet you mentioned were happening, the afrho parameter actually had a nearly constat trend. Incidentally, also for this reason the astronomers frequently prefer to talk about the afrho parameter, instead of the apparent brightness -i.e. m1- when dealing with cometary activity...
                                > >
                                > > Bye,
                                > > Giovanni
                                > >
                                > -----------------------------------------------------------------
                                >
                                > Sostero wrote ( Apr. 6 ) :
                                >
                                > > Hello John,
                                > > thanks for yours comments.
                                > >
                                > >
                                > >> Perhaps a word of caution is advisable here.
                                > >>
                                > >
                                > > The point I raised is obviously based on the reliability of the visual estimations we have seen so far. If there is any doubt about the consistency of this data, well then question drops.
                                > >
                                > > In the past I made just a few visual estimation of comets myself, so for this I mainly rely on the experience of trusted observers (as you and Juan).
                                > >
                                > > Bye,
                                > > Giovanni
                                > >
                                >
                              • Jakub Černý
                                Dear Juan, ... While I am saying that im sometimes observing meteors visually just to lie under sky, because visual observations doesnt have much sense
                                Message 15 of 26 , May 6, 2011
                                  Dear Juan,



                                  > A possible conclusion ? Well ... Reading some of your words ( and
                                  > some other older posts in this list ) ... If only CCD photometry rules,
                                  > and m1 estimates are sometimes judged to be without value for any good
                                  > cometary work ... maybe the "old-style" visual observers like me ( I am
                                  > near 60 now ) must retire from seeking the best dark mountain skies,
                                  > travelling thousands of kilometers on rugged roads, and finally come
                                  > back home to a ( well deserved ) rest ...

                                  While I am saying that im sometimes observing meteors visually just to lie
                                  under sky, because visual observations doesnt have much sense nowdays,
                                  situation about visual comet observing is different. You still have very
                                  long line of data behind with same methodics. As far as i see in CCD
                                  observations, they all have some sense now, but it is hard to analyze it
                                  while there can be even 2 magnitude difference caused by technique
                                  expositions chips and methods of obtaining observation. I think that there
                                  is absolutely no reason to stop doing visual photometry now and interrupt
                                  very long line of data, just when we are geting multiple return observations
                                  of many periodic comets!



                                  You can take this as a opinion of man who is doing brightness evolution
                                  analysis from visual observations for more then 12 years.



                                  I hope you will never stop doing such a great job!



                                  Respect!



                                  Best regards,

                                  Jakub Cerny

                                  Czech Republic



                                  [Non-text portions of this message have been removed]
                                • Juan José González Suárez
                                  Dear Giovanny and Jakub, As you express clearly, Giovanni, ( regarding the monitoring of cometary behavior ), afrho parameter has an obvious importance related
                                  Message 16 of 26 , May 6, 2011
                                    Dear Giovanny and Jakub,

                                    As you express clearly, Giovanni, ( regarding the monitoring of
                                    cometary behavior ), afrho parameter has an obvious importance related
                                    to the dust production rate; the other basic parameter that govern the
                                    activity of the comet ( and the size of the coma ) being the gas
                                    production rate. Studies on the correlation heliocentric magnitude <->
                                    OH rate are well known.

                                    We ( modest visual observers ) simply are trying to provide the best
                                    available data on new and periodic comets.

                                    As Jakub says, " ... I think that there is absolutely no reason to
                                    stop doing visual photometry now and interrupt very long line of data,
                                    just when we are geting multiple return observations of many periodic
                                    comets ... ".

                                    So ... Let's go out and observe ( ... weather and light pollution
                                    permitting ... ) using reliable catalogues for comparison stars.

                                    Best wishes and clear skies,


                                    Juan Jose Gonzalez

                                    P.S.: Thanks for your words on my work. But ... sincerely, I don't see
                                    myself ( with telescope ) on a mountain top at 75 years old ( male life
                                    expectancy in Spain ... ).


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

                                    Giovanni Sostero wrote :

                                    > Dears Jakub and Juan,
                                    > thanks for yours reply.
                                    >
                                    > I comment here only about the secon point raised by J:J. (value of visual estimates of comers). I think that there was a misunderstading here: it was not my intention to say that visual observations are useless. What I wanted to say was, instead, that for *physical* considerations about comet's behaviour, the professionals prefer to deal with other parameters (like the afrho quantity). This is pretty clear browsing through the scientific literature.
                                    > IMHO visual estimates of comets are still pretty interesting and important (e.g. For a first estimate of a given comet's behaviour). Apart of this, as an amateur, I consider that the work that you, and others, are performing regularly on many comets, is of the uppermost importance, and a pleasure for itself (I always feel a form of envy, reading about yours expeditions under dark, mountain skies).
                                    > Hope that you will continue this activity well over your eighties.
                                    >
                                    > Bye,
                                    > Giovanni
                                    >
                                    -------------------------------------------------------

                                    Jakub Cerny wrote :

                                    > Dear Juan,
                                    >
                                    > While I am saying that im sometimes observing meteors visually just to lie
                                    > under sky, because visual observations doesnt have much sense nowdays,
                                    > situation about visual comet observing is different. You still have very
                                    > long line of data behind with same methodics. As far as i see in CCD
                                    > observations, they all have some sense now, but it is hard to analyze it
                                    > while there can be even 2 magnitude difference caused by technique
                                    > expositions chips and methods of obtaining observation. I think that there
                                    > is absolutely no reason to stop doing visual photometry now and interrupt
                                    > very long line of data, just when we are geting multiple return observations
                                    > of many periodic comets!
                                    >
                                    > You can take this as a opinion of man who is doing brightness evolution
                                    > analysis from visual observations for more then 12 years.
                                    >
                                    > I hope you will never stop doing such a great job!
                                    >
                                    > Respect!
                                    >
                                    > Best regards,
                                    >
                                    > Jakub Cerny
                                  • J.P.Navarro Pina
                                    Hi all , I totally agree with J.J. and Jakub, visual observations of comets are of great scientific importance when analyzing and studying the light curves of
                                    Message 17 of 26 , May 6, 2011
                                      Hi all ,


                                      I totally agree with J.J. and Jakub, visual observations of comets are of great scientific importance when analyzing and studying the light curves of comets, with the visual measurements can study production rates of water and other gases in comets, as well as production rates also unfortunately today the CCD's are more in use but visual observation of comets must follow.


                                      regards , J.P.Navarro .
                                      ----- Original Message -----
                                      From: Juan José González Suárez
                                      To: COML
                                      Sent: Saturday, May 07, 2011 12:53 AM
                                      Subject: [comets-ml] Re: Betting on CCDs vs. Observers ? ( was : The full spectrum of Elenin 'news' ... )



                                      Dear Giovanny and Jakub,

                                      As you express clearly, Giovanni, ( regarding the monitoring of
                                      cometary behavior ), afrho parameter has an obvious importance related
                                      to the dust production rate; the other basic parameter that govern the
                                      activity of the comet ( and the size of the coma ) being the gas
                                      production rate. Studies on the correlation heliocentric magnitude <->
                                      OH rate are well known.

                                      We ( modest visual observers ) simply are trying to provide the best
                                      available data on new and periodic comets.

                                      As Jakub says, " ... I think that there is absolutely no reason to
                                      stop doing visual photometry now and interrupt very long line of data,
                                      just when we are geting multiple return observations of many periodic
                                      comets ... ".

                                      So ... Let's go out and observe ( ... weather and light pollution
                                      permitting ... ) using reliable catalogues for comparison stars.

                                      Best wishes and clear skies,

                                      Juan Jose Gonzalez

                                      P.S.: Thanks for your words on my work. But ... sincerely, I don't see
                                      myself ( with telescope ) on a mountain top at 75 years old ( male life
                                      expectancy in Spain ... ).

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

                                      Giovanni Sostero wrote :

                                      > Dears Jakub and Juan,
                                      > thanks for yours reply.
                                      >
                                      > I comment here only about the secon point raised by J:J. (value of visual estimates of comers). I think that there was a misunderstading here: it was not my intention to say that visual observations are useless. What I wanted to say was, instead, that for *physical* considerations about comet's behaviour, the professionals prefer to deal with other parameters (like the afrho quantity). This is pretty clear browsing through the scientific literature.
                                      > IMHO visual estimates of comets are still pretty interesting and important (e.g. For a first estimate of a given comet's behaviour). Apart of this, as an amateur, I consider that the work that you, and others, are performing regularly on many comets, is of the uppermost importance, and a pleasure for itself (I always feel a form of envy, reading about yours expeditions under dark, mountain skies).
                                      > Hope that you will continue this activity well over your eighties.
                                      >
                                      > Bye,
                                      > Giovanni
                                      >
                                      -------------------------------------------------------

                                      Jakub Cerny wrote :

                                      > Dear Juan,
                                      >
                                      > While I am saying that im sometimes observing meteors visually just to lie
                                      > under sky, because visual observations doesnt have much sense nowdays,
                                      > situation about visual comet observing is different. You still have very
                                      > long line of data behind with same methodics. As far as i see in CCD
                                      > observations, they all have some sense now, but it is hard to analyze it
                                      > while there can be even 2 magnitude difference caused by technique
                                      > expositions chips and methods of obtaining observation. I think that there
                                      > is absolutely no reason to stop doing visual photometry now and interrupt
                                      > very long line of data, just when we are geting multiple return observations
                                      > of many periodic comets!
                                      >
                                      > You can take this as a opinion of man who is doing brightness evolution
                                      > analysis from visual observations for more then 12 years.
                                      >
                                      > I hope you will never stop doing such a great job!
                                      >
                                      > Respect!
                                      >
                                      > Best regards,
                                      >
                                      > Jakub Cerny






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



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                                      [Non-text portions of this message have been removed]
                                    • Burkhard
                                      ... I find it a little bit odd and funny, that with every brighter comet that comes along the discussion starts will it survive perihelion? Some examples
                                      Message 18 of 26 , May 7, 2011
                                        >„the comet may be intrinsically a bit too faint to even survive perihelion passage"

                                        I find it a little bit odd and funny, that with every brighter comet that comes along the discussion starts "will it survive perihelion?"

                                        Some examples from this list:

                                        C/2002 V1
                                        „I'd think the comet's chances for perihelion survival will be marginal, at best."

                                        C/2004 F4
                                        „places it a full magnitude below the survival cut-off for an r of 0.169 AU"

                                        C/2006 M4
                                        „it may be possible that it will not survive a close perihelion"

                                        C/2006 P1
                                        „a good likelihood of this comet not even surviving all the way to perihelion passage"

                                        C/2009 R1
                                        „more likely to not even survive its perihelion passage"


                                        All these have survived, so it seems to me there's lot that we still don´t know and can't calculate...
                                        "Comets are like cats; they have tails, and they do precisely what they want." - David H. Levy

                                        Kind Regards and CS
                                        Burkhard Leitner


                                        --- In comets-ml@yahoogroups.com, Jakub Èerný <kaos@...> wrote:
                                        >
                                        > Dear Giovanni and all,
                                        >
                                        >
                                        >
                                        > Yes withcomets it is always a roulette J. The best we have at this moment is
                                        > empiric formula of John Bortle ( " Post-Perihelion survival of comets with
                                        > small q ", ICQ Vol. 13, No. 3 - Whole Number 79, July 1991, pp. 89-91. )
                                        > which giving value H10 = 9.89 mag in case of comet Elenin, actually its
                                        > absolute magnitude is near 10 mag.
                                        >
                                        >
                                        >
                                        > For example same formula give for comet C/2006 P1 (McNaught) gave value H10
                                        > = 8.02 mag while its absolute mag shortly before perihelion passage was 6
                                        > mag (with similar "n" parameter as its calculated for Elenin), so comet was
                                        > "safe".
                                        >
                                      • Jakub Černý
                                        Hello Burkhard and all, Thanks for interesting (and funny :) reading, I just have 2 notes. 1) C/2009 R1 actually did not survive perihelion. 2) For
                                        Message 19 of 26 , May 7, 2011
                                          Hello Burkhard and all,



                                          Thanks for interesting (and funny :) reading, I just have 2 notes.



                                          1) C/2009 R1 actually did not survive perihelion.



                                          2) For many others comets can be main confusing factor, the speed of activity groving, comets like C/2002 V1 and C/2006 P1 looks long before perihelion as weak with too little nucleus, but then later much more fractions of it gets active, and when they reach perihellion their absolute magnitude was far away from critical barrier



                                          Predicting comets is like predicting weather, there are many unknown and random factors, but that is not a reason why should I také umbrella when walking through sunny day J.



                                          You can be sure that predictions will never be one hundred percent accurate, still we have to do them and later update out theorys to make more and more acurate predictions.



                                          Anyway when I look at fresh Elenin data, comet brightening also very fast and if it is not only temporary and will continue, it may move its absolute magnitude to safe zone!



                                          Best regards,

                                          Jakub Cerny





                                          From: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] On Behalf Of Burkhard
                                          Sent: Saturday, May 07, 2011 12:22 PM
                                          To: comets-ml@yahoogroups.com
                                          Subject: [comets-ml] Re: The full spectrum of Elenin 'news' ...







                                          >„the comet may be intrinsically a bit too faint to even survive perihelion passage"

                                          I find it a little bit odd and funny, that with every brighter comet that comes along the discussion starts "will it survive perihelion?"

                                          Some examples from this list:

                                          C/2002 V1
                                          „I'd think the comet's chances for perihelion survival will be marginal, at best."

                                          C/2004 F4
                                          „places it a full magnitude below the survival cut-off for an r of 0.169 AU"

                                          C/2006 M4
                                          „it may be possible that it will not survive a close perihelion"

                                          C/2006 P1
                                          „a good likelihood of this comet not even surviving all the way to perihelion passage"

                                          C/2009 R1
                                          „more likely to not even survive its perihelion passage"

                                          All these have survived, so it seems to me there's lot that we still don´t know and can't calculate...
                                          "Comets are like cats; they have tails, and they do precisely what they want." - David H. Levy

                                          Kind Regards and CS
                                          Burkhard Leitner

                                          --- In comets-ml@yahoogroups.com <mailto:comets-ml%40yahoogroups.com> , Jakub Èerný <kaos@...> wrote:
                                          >
                                          > Dear Giovanni and all,
                                          >
                                          >
                                          >
                                          > Yes withcomets it is always a roulette J. The best we have at this moment is
                                          > empiric formula of John Bortle ( " Post-Perihelion survival of comets with
                                          > small q ", ICQ Vol. 13, No. 3 - Whole Number 79, July 1991, pp. 89-91. )
                                          > which giving value H10 = 9.89 mag in case of comet Elenin, actually its
                                          > absolute magnitude is near 10 mag.
                                          >
                                          >
                                          >
                                          > For example same formula give for comet C/2006 P1 (McNaught) gave value H10
                                          > = 8.02 mag while its absolute mag shortly before perihelion passage was 6
                                          > mag (with similar "n" parameter as its calculated for Elenin), so comet was
                                          > "safe".
                                          >





                                          [Non-text portions of this message have been removed]
                                        • Rodney Austin
                                          I well remember the embarrasing predictions made about several comets in the past, by the news media, and one or two others who presumably should have been
                                          Message 20 of 26 , May 7, 2011
                                            I well remember the embarrasing 'predictions' made about several comets in
                                            the past, by the news media, and one or two others who presumably should
                                            have been more cautious. In particular the predictions of my last one. The
                                            only accurate prediction I saw published came from John Bortle who warned of
                                            its similarity to Comet Cunningham. It's rate of brightening changed
                                            abruptly within two days of reaching the heliocentric distance that John
                                            reckoned would be critical - a pity, but that's life.
                                            Cheers
                                            Rod Austin


                                            [Non-text portions of this message have been removed]
                                          • comet_elenin
                                            ... Replying to all those scoffing at my magnitude -20 suggestion! =D I saw your group in my blog stats. Though I ve joined, I see most of you are really
                                            Message 21 of 26 , May 8, 2011
                                              --- In comets-ml@yahoogroups.com, Daniel Fischer <dfischer@...> wrote:
                                              >
                                              > Oh wondrous internet, if you just look around you fill find *any* kind of opinion
                                              > on any kind of subject, comet Elenin included - and I don't mean the totally looney
                                              > conspiracy websites. But what about the following posting one of several Elenin blogs:
                                              > http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-brighter-than.html - here
                                              > it is claimed that a combination of optical effects might raise the comet's apparent
                                              > brightness to, gasp, -20 mag.! Meanwhile on another blog L. Elenin himself speaks out:
                                              > http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected - here
                                              > a +4 mag. peak is foreseen. Does that match the general feeling in the community?
                                              >
                                              > Dan
                                              >


                                              Replying to all those scoffing at my magnitude -20 suggestion! =D

                                              I saw your group in my blog stats. Though I've joined, I see most of you are really into comets, whereas my interest peeks on the advent of a possible great comet and then fades until the next great possible great comet is discovered. =D

                                              In regards to magnitude -20. Yeah, it's highly unlikely, but it's not completely improbable, right? I know that it has never happened aside from the sun grazers, but lets say comet Elenin did end up being a great comet by breaking up and became very active and was extremely dusty, wouldn't it have a chance during its inferior conjunction? Anyone know off the top of their head if we've had a comet in the past at around 0.23 AU from earth and just slightly above the ecliptic during conjunction? Intuitively this particular configuration would be optimal conditions for the forward scattering effect to occur, it feels to me. Not too close, not too far, not to high, not too low. Just right, it feels to me.

                                              I love being wrong! So don't hesitate. =)
                                            • jbortle@aol.com
                                              Dan, the probability of Comet Elenin ever reaching a maximum brightness of anything like -20 is absolutely nil. Whether it were to break up, or otherwise,
                                              Message 22 of 26 , May 8, 2011
                                                Dan, the probability of Comet Elenin ever reaching a maximum brightness of
                                                anything like -20 is absolutely nil. Whether it were to break up, or
                                                otherwise, this is an intrinsically very faint/small/inactive object to begin
                                                with. That seriously limits its potential for becoming anything of any real
                                                significance in the area of apparent brightness.

                                                Historically, comets from the Oort cloud are poor performers, even those
                                                that were initially supposed to be intrinsically quite bright and much
                                                brighter than Comet Elenin is. This situation has been demonstrated repeatedly
                                                over the past century. I am not familiar with a single instance in which one
                                                of these objects became either truly "spectacular", or a Great Comet.

                                                The very brightest I currently feel Comet Elenin might attain - if it
                                                should even survive to perihelion passage at all - might very briefly be
                                                somewhat brighter than zero magnitude. Even that figure would be due only to a
                                                high degree of forward scattering and a relatively high degree of dust
                                                output. However, given the comet's positional circumstances when such a
                                                situation might occur, the comet would still be totally unobservable directly by
                                                the average ground based observer, simply because of its proximity to the
                                                Sun. As soon as the comet would draw away from the immediate vicinity of the
                                                Sun it would quickly return to being a faint object.

                                                To address your question about other comets in the past having encounters
                                                under similar orbital circumstances, yes, there have been others. However,
                                                only those with intrinsic brightnesses perhaps 100 times, or so, greater
                                                than Comet Elenin currently appears to have became impressive objects.

                                                In short, neither Comet Elenin, nor its orbital circumstances, offers much
                                                in the way of any real possibility of becoming more than just a minor
                                                cometary event in late 2011 for the average observer. However, for serious
                                                comet watchers, it could well prove quite interesting. So, I'd stick with the
                                                figure for the maximum brightness purpose in L. Elenin's blog in future when
                                                writing anything intended for the average observer/reader if I were you.

                                                J.Bortle




                                                In a message dated 5/8/2011 7:38:15 A.M. Eastern Daylight Time,
                                                james-william-kincaid-lll@... writes:






                                                --- In _comets-ml@yahoogroups.com_ (mailto:comets-ml@yahoogroups.com) ,
                                                Daniel Fischer <dfischer@...> wrote:
                                                >
                                                > Oh wondrous internet, if you just look around you fill find *any* kind
                                                of opinion
                                                > on any kind of subject, comet Elenin included - and I don't mean the
                                                totally looney
                                                > conspiracy websites. But what about the following posting one of several
                                                Elenin blogs:
                                                >
                                                _http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-brighter-than.html_
                                                (http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-brighter-than.html) - here
                                                > it is claimed that a combination of optical effects might raise the
                                                comet's apparent
                                                > brightness to, gasp, -20 mag.! Meanwhile on another blog L. Elenin
                                                himself speaks out:
                                                >
                                                _http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected_
                                                (http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected) - here
                                                > a +4 mag. peak is foreseen. Does that match the general feeling in the
                                                community?
                                                >
                                                > Dan
                                                >

                                                Replying to all those scoffing at my magnitude -20 suggestion! =D

                                                I saw your group in my blog stats. Though I've joined, I see most of you
                                                are really into comets, whereas my interest peeks on the advent of a
                                                possible great comet and then fades until the next great possible great comet is
                                                discovered. =D

                                                In regards to magnitude -20. Yeah, it's highly unlikely, but it's not
                                                completely improbable, right? I know that it has never happened aside from the
                                                sun grazers, but lets say comet Elenin did end up being a great comet by
                                                breaking up and became very active and was extremely dusty, wouldn't it have
                                                a chance during its inferior conjunction? Anyone know off the top of their
                                                head if we've had a comet in the past at around 0.23 AU from earth and just
                                                slightly above the ecliptic during conjunction? Intuitively this
                                                particular configuration would be optimal conditions for the forward scattering
                                                effect to occur, it feels to me. Not too close, not too far, not to high, not
                                                too low. Just right, it feels to me.

                                                I love being wrong! So don't hesitate. =)





                                                [Non-text portions of this message have been removed]
                                              • jbortle@aol.com
                                                Sorry, Dan, my reply was intended for James, not you. J.Bortle In a message dated 5/8/2011 8:44:47 A.M. Eastern Daylight Time, jbortle@aol.com writes: Dan, the
                                                Message 23 of 26 , May 8, 2011
                                                  Sorry, Dan, my reply was intended for James, not you.

                                                  J.Bortle


                                                  In a message dated 5/8/2011 8:44:47 A.M. Eastern Daylight Time,
                                                  jbortle@... writes:




                                                  Dan, the probability of Comet Elenin ever reaching a maximum brightness of
                                                  anything like -20 is absolutely nil. Whether it were to break up, or
                                                  otherwise, this is an intrinsically very faint/small/inactive object to
                                                  begin
                                                  with. That seriously limits its potential for becoming anything of any
                                                  real
                                                  significance in the area of apparent brightness.

                                                  Historically, comets from the Oort cloud are poor performers, even those
                                                  that were initially supposed to be intrinsically quite bright and much
                                                  brighter than Comet Elenin is. This situation has been demonstrated
                                                  repeatedly
                                                  over the past century. I am not familiar with a single instance in which
                                                  one
                                                  of these objects became either truly "spectacular", or a Great Comet.

                                                  The very brightest I currently feel Comet Elenin might attain - if it
                                                  should even survive to perihelion passage at all - might very briefly be
                                                  somewhat brighter than zero magnitude. Even that figure would be due only
                                                  to a
                                                  high degree of forward scattering and a relatively high degree of dust
                                                  output. However, given the comet's positional circumstances when such a
                                                  situation might occur, the comet would still be totally unobservable
                                                  directly by
                                                  the average ground based observer, simply because of its proximity to the
                                                  Sun. As soon as the comet would draw away from the immediate vicinity of
                                                  the
                                                  Sun it would quickly return to being a faint object.

                                                  To address your question about other comets in the past having encounters
                                                  under similar orbital circumstances, yes, there have been others. However,
                                                  only those with intrinsic brightnesses perhaps 100 times, or so, greater
                                                  than Comet Elenin currently appears to have became impressive objects.

                                                  In short, neither Comet Elenin, nor its orbital circumstances, offers much
                                                  in the way of any real possibility of becoming more than just a minor
                                                  cometary event in late 2011 for the average observer. However, for serious
                                                  comet watchers, it could well prove quite interesting. So, I'd stick with
                                                  the
                                                  figure for the maximum brightness purpose in L. Elenin's blog in future
                                                  when
                                                  writing anything intended for the average observer/reader if I were you.

                                                  J.Bortle




                                                  In a message dated 5/8/2011 7:38:15 A.M. Eastern Daylight Time,
                                                  _james-william-kincaid-lll@..._
                                                  (mailto:james-william-kincaid-lll@...) writes:

                                                  --- In __comets-ml@yahoogroups.com_ (mailto:_comets-ml@yahoogroups.com) _
                                                  (mailto:_comets-ml@yahoogroups.com_ (mailto:comets-ml@yahoogroups.com) ) ,
                                                  Daniel Fischer <dfischer@...> wrote:
                                                  >
                                                  > Oh wondrous internet, if you just look around you fill find *any* kind
                                                  of opinion
                                                  > on any kind of subject, comet Elenin included - and I don't mean the
                                                  totally looney
                                                  > conspiracy websites. But what about the following posting one of several
                                                  Elenin blogs:
                                                  >
                                                  __http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-brighter-than
                                                  .html__
                                                  (http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-brighter-than.html_)
                                                  (_http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-brighter-than
                                                  .html_ (http://comet-elenin.blogspot.com/2011/05/comet-elenin-may-be-bright
                                                  er-than.html) ) - here
                                                  > it is claimed that a combination of optical effects might raise the
                                                  comet's apparent
                                                  > brightness to, gasp, -20 mag.! Meanwhile on another blog L. Elenin
                                                  himself speaks out:
                                                  >
                                                  __http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expect
                                                  ed__
                                                  (http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected_)
                                                  (_http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expect
                                                  ed_
                                                  (http://spaceobs.org/en/2011/05/02/comet-elenin-may-be-brighter-than-expected) ) - here
                                                  > a +4 mag. peak is foreseen. Does that match the general feeling in the
                                                  community?
                                                  >
                                                  > Dan
                                                  >

                                                  Replying to all those scoffing at my magnitude -20 suggestion! =D

                                                  I saw your group in my blog stats. Though I've joined, I see most of you
                                                  are really into comets, whereas my interest peeks on the advent of a
                                                  possible great comet and then fades until the next great possible great
                                                  comet is
                                                  discovered. =D

                                                  In regards to magnitude -20. Yeah, it's highly unlikely, but it's not
                                                  completely improbable, right? I know that it has never happened aside from
                                                  the
                                                  sun grazers, but lets say comet Elenin did end up being a great comet by
                                                  breaking up and became very active and was extremely dusty, wouldn't it
                                                  have
                                                  a chance during its inferior conjunction? Anyone know off the top of their
                                                  head if we've had a comet in the past at around 0.23 AU from earth and
                                                  just
                                                  slightly above the ecliptic during conjunction? Intuitively this
                                                  particular configuration would be optimal conditions for the forward
                                                  scattering
                                                  effect to occur, it feels to me. Not too close, not too far, not to high,
                                                  not
                                                  too low. Just right, it feels to me.

                                                  I love being wrong! So don't hesitate. =)

                                                  [Non-text portions of this message have been removed]





                                                  [Non-text portions of this message have been removed]
                                                • comet_elenin
                                                  ... [Rest of full quote deleted by admin] Thanks for your reply. The beauty of it all is that we will get to see the actual answers in a few months from now.
                                                  Message 24 of 26 , May 9, 2011
                                                    --- In comets-ml@yahoogroups.com, jbortle@... wrote:
                                                    >
                                                    > Dan, the probability of Comet Elenin ever reaching a maximum brightness of
                                                    > anything like -20 is absolutely nil.

                                                    [Rest of full quote deleted by admin]


                                                    Thanks for your reply. The beauty of it all is that we will get to see the actual answers in a few months from now.
                                                  Your message has been successfully submitted and would be delivered to recipients shortly.