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Comet 2011 L4, Where Are The Mag Estimates?

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  • cnj999
    I must say that the number of reliable, or in fact any sort of, magnitude determinations for this comet have been most disappointingly meager since it entered
    Message 1 of 17 , Mar 27, 2013
      I must say that the number of reliable, or in fact any sort of, magnitude
      determinations for this comet have been most disappointingly meager since
      it entered the northern hemisphere's skies. This situation is in dramatic
      contrast to the volume of southern hemisphere data that preceded perihelion.
      The lack of visual observations has been especially notable over the past
      week, or so, when almost nothing in the way of reports are apparent here, or
      in the CometObs file.

      I would, however, again like to caution those who do attempt visual
      photometric observations to employ an extra degree of care with C/2011 L4 so as
      not to integrate the beginnings of this comet's bright tail into their
      extra-focal comparisons. I feel a number may have done this recently. I viewed
      the comet last evening with large binoculars and noted the coma to be
      significantly fainter than might have been otherwise anticipated from some of
      last week's reported sighting by others. I would note that my comparison stars
      were also nearly at the same altitude as the comet, negating virtually any
      need for arbitrary extinction corrections to be appplied.

      Given that the coma appears all but star-like (only around 3'-4' in
      diameter) to the unaided eye and not in any way separate from the tail, I am
      particularly troubled by the apparent brightness of some of the reported
      determinations made without instrumentation.

      J.Bortle




      [Non-text portions of this message have been removed]
    • Phillip Creed
      John, One thing we need in the Northern Hemisphere to make a mag estimate is to the ability to *actually see* the comet. The weather s been absolutely
      Message 2 of 17 , Mar 27, 2013
        John,

        One thing we need in the Northern Hemisphere to make a mag estimate is to the ability to *actually see* the comet. The weather's been absolutely miserable in the Eastern U.S., where a large portion of the populace (and comet observers) is located, and similar stories abound in the UK and northern Europe.

        Here in Ohio, this month's weather hasn't merely been hell for comet observers; it's been pure hell. As in, start with raw, crude bituminous hell mined from deep within the earth, then fractionally distill it into pure, complete and utter malevolence towards stargazers. I have to bite my tongue, as further descriptions of Ohio's weather this month will devolve into a Sam Kinison-esque tirade.

        Australian observers not only have the benefit of less atmospheric extinction (less potential error), but they also had the benefit of better weather. Some parts of Australia have a bump in winter cloudiness due to a Mediterranean-like climate (particularly Perth, but also Melbourne), but the comet was visible in late summer down there. Some parts of Australia are cloudier than others, but they're not 70-80% overcast in February/March like it's been here in the Northeastern U.S. and Europe.

        Furthermore, it's tough enough to get clear skies overhead this month, but much more so near the horizon. We have an active jet stream in the Northern Hemisphere, and when you're looking for comets in the west, those fast-moving cirrus clouds carried by the jet stream are killers. A cirrus cloud bank that's 6 miles up can obscure up to 5-deg above the horizon even if they're 100km (62 miles) away, and can obscure up to 3-deg if they're 150km (93 miles) distant. I'm guessing some observers are not factoring this in. They see that Clear Sky Chart says, "clear", and maybe it verifies, but CSC only accounts for the conditions *overhead*. Clicking on the actual forecast sky map on CSC, seeing how well it verifies with current satellite imagery, and adjusting site selection to account for incoming/outgoing clouds on the horizon is the key.

        I do agree that the coma is not terribly bright, and that a lot of naked-eye sightings are the result of the coma being integrated into the first few arc minutes of the tail. I saw it on March 20.03 UTC under a very limited time frame and estimated m1 ~ 3.1. The estimate was made under such a time crunch I didn't even bother reporting to ICQ or other sources since I felt it was too crude an estimate.

        Clear Skies,
        Phil

        --- In comets-ml@yahoogroups.com, jbortle@... wrote:
        >
        > I must say that the number of reliable, or in fact any sort of, magnitude
        > determinations for this comet have been most disappointingly meager since
        > it entered the northern hemisphere's skies. This situation is in dramatic
        > contrast to the volume of southern hemisphere data that preceded perihelion.
        > The lack of visual observations has been especially notable over the past
        > week, or so, when almost nothing in the way of reports are apparent here, or
        > in the CometObs file.
        >
        > I would, however, again like to caution those who do attempt visual
        > photometric observations to employ an extra degree of care with C/2011 L4 so as
        > not to integrate the beginnings of this comet's bright tail into their
        > extra-focal comparisons. I feel a number may have done this recently. I viewed
        > the comet last evening with large binoculars and noted the coma to be
        > significantly fainter than might have been otherwise anticipated from some of
        > last week's reported sighting by others. I would note that my comparison stars
        > were also nearly at the same altitude as the comet, negating virtually any
        > need for arbitrary extinction corrections to be appplied.
        >
        > Given that the coma appears all but star-like (only around 3'-4' in
        > diameter) to the unaided eye and not in any way separate from the tail, I am
        > particularly troubled by the apparent brightness of some of the reported
        > determinations made without instrumentation.
        >
        > J.Bortle
        >
        >
        >
        >
        > [Non-text portions of this message have been removed]
        >
      • Ellen Papenburg
        Well, yesterday it was suddenly clear like a bell in nine days. So out we went on the road to our established spot at a farm with a clear view on the horizon.
        Message 3 of 17 , Mar 27, 2013
          Well, yesterday it was suddenly clear like a bell in nine days. So out
          we went on the road to our established spot at a farm with a clear view
          on the horizon.

          It was much "warmer" than 10 days ago, but cold nevertheless...
          resulting in me again shedding tears (and not of joy) otherwise I might
          have done an attempt to (gu)estimate its magnitude, especially now it's
          surrounded by some visible stars, but I have to say I could barely see
          it through a 15x70 binocs, almost more a figment of my imagination.

          I can only give you a "it's diminished greatly since March 17". But
          that's not very satisfactory, is it now! Only an indication of its
          expected behaviour.

          I did take pics, but if they worked out will know later today when I
          make some time to process.... But for magnitude determination those
          won't be very helpful.

          Ellen - SW Ontario - for me it was never a naked-eye object....

          On 27/03/2013 9:16 AM, jbortle@... wrote:
          >
          > I must say that the number of reliable, or in fact any sort of, magnitude
          > determinations for this comet have been most disappointingly meager since
          > it entered the northern hemisphere's skies. This situation is in dramatic
          > contrast to the volume of southern hemisphere data that preceded
          > perihelion.
          > The lack of visual observations has been especially notable over the past
          > week, or so, when almost nothing in the way of reports are apparent
          > here, or
          > in the CometObs file.
          >
          > I would, however, again like to caution those who do attempt visual
          > photometric observations to employ an extra degree of care with C/2011
          > L4 so as
          > not to integrate the beginnings of this comet's bright tail into their
          > extra-focal comparisons. I feel a number may have done this recently.
          > I viewed
          > the comet last evening with large binoculars and noted the coma to be
          > significantly fainter than might have been otherwise anticipated from
          > some of
          > last week's reported sighting by others. I would note that my
          > comparison stars
          > were also nearly at the same altitude as the comet, negating virtually
          > any
          > need for arbitrary extinction corrections to be appplied.
          >
          > Given that the coma appears all but star-like (only around 3'-4' in
          > diameter) to the unaided eye and not in any way separate from the
          > tail, I am
          > particularly troubled by the apparent brightness of some of the reported
          > determinations made without instrumentation.
          >
          > J.Bortle
          >



          [Non-text portions of this message have been removed]
        • aum22355
          Hi: Did the number of magnitude estimates stay steady from the Southern hemisphere observations, or did they drop towards the end? I was just thinking that one
          Message 4 of 17 , Mar 27, 2013
            Hi:
            Did the number of magnitude estimates stay steady from the Southern hemisphere observations, or did they drop towards the end?
            I was just thinking that one reason there were more is that the Northern hemisphere observers have had to deal with twilight in the beginning of their observing window, while with the Southern observers twilight was a factor towards the end of their observing window.
            Just a thought...
            Michael Gille


            -----Original Message-----
            From: Alan Hale <ahale@...>
            To: comets-ml <comets-ml@yahoogroups.com>
            Sent: Wed, Mar 27, 2013 11:32 am
            Subject: Re: [comets-ml] Comet 2011 L4, Where Are The Mag Estimates?





            Well, for what it's worth, the weather in this part of the world last week
            wasn't all that good either ‹ lots of clouds, plus windblown dust (this is
            the windy season here in NM) -- plus, I had a lot of social commitments last
            week that took up a lot of my evenings. And now, of course, the full moon
            (although the skies have been clear for the most part the past few nights).

            I did observe the comet Sunday evening under relatively good sky conditions,
            although obviously in a moon-brightened sky. March 25.10, m1=3.9 in 10x50
            binoculars; although I was able to use nearby stars as comparison objects,
            since the elevation is still low and even a couple of degrees can made a
            non-trivial difference in terms of extinction I still had to apply some
            correction for differential extinction. It's possible that the moonlight
            affected the magnitude measurement to some extent, but the comet is clearly
            quite a bit fainter than it was earlier this month.

            Sincerely,

            Alan

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









            [Non-text portions of this message have been removed]
          • John Menke
            Hey, Phillip--right on! And it is not just comet observing. Here in Maryland, downwind from you, not only has the comet been a vague sometimes visitor to our
            Message 5 of 17 , Mar 27, 2013
              Hey, Phillip--right on! And it is not just comet observing. Here in
              Maryland, downwind from you, not only has the comet been a vague
              sometimes visitor to our skies (I've seen it twice, and actually got an
              image or two), my own photometric and spectroscopic work has suffered
              the "bituminous hell" you described. Ah, you say, don't fret, for there
              is always another day (night) when "the star" will be visible. But
              throw in a rotation period of 1.19 days on a short observing window, you
              can guarantee that every fifth day will be bituminous. And will land on
              the most interesting, most unique part of the phase curve. Three months
              after starting observations, the target is sinking faster and faster,
              and that hole in the phase graph continues to linger like the groundhog
              in Murray's movie.

              John Menke
              Cloud-gazing in Maryland
              menkescientific.com

              On 3/27/2013 10:28 AM, Phillip Creed wrote:
              > John,
              >
              > One thing we need in the Northern Hemisphere to make a mag estimate is to the ability to *actually see* the comet. The weather's been absolutely miserable in the Eastern U.S., where a large portion of the populace (and comet observers) is located, and similar stories abound in the UK and northern Europe.
              >
              > Here in Ohio, this month's weather hasn't merely been hell for comet observers; it's been pure hell. As in, start with raw, crude bituminous hell mined from deep within the earth, then fractionally distill it into pure, complete and utter malevolence towards stargazers. I have to bite my tongue, as further descriptions of Ohio's weather this month will devolve into a Sam Kinison-esque tirade.
              >
              > Australian observers not only have the benefit of less atmospheric extinction (less potential error), but they also had the benefit of better weather. Some parts of Australia have a bump in winter cloudiness due to a Mediterranean-like climate (particularly Perth, but also Melbourne), but the comet was visible in late summer down there. Some parts of Australia are cloudier than others, but they're not 70-80% overcast in February/March like it's been here in the Northeastern U.S. and Europe.
              >
              > Furthermore, it's tough enough to get clear skies overhead this month, but much more so near the horizon. We have an active jet stream in the Northern Hemisphere, and when you're looking for comets in the west, those fast-moving cirrus clouds carried by the jet stream are killers. A cirrus cloud bank that's 6 miles up can obscure up to 5-deg above the horizon even if they're 100km (62 miles) away, and can obscure up to 3-deg if they're 150km (93 miles) distant. I'm guessing some observers are not factoring this in. They see that Clear Sky Chart says, "clear", and maybe it verifies, but CSC only accounts for the conditions *overhead*. Clicking on the actual forecast sky map on CSC, seeing how well it verifies with current satellite imagery, and adjusting site selection to account for incoming/outgoing clouds on the horizon is the key.
              >
              > I do agree that the coma is not terribly bright, and that a lot of naked-eye sightings are the result of the coma being integrated into the first few arc minutes of the tail. I saw it on March 20.03 UTC under a very limited time frame and estimated m1 ~ 3.1. The estimate was made under such a time crunch I didn't even bother reporting to ICQ or other sources since I felt it was too crude an estimate.
              >
              > Clear Skies,
              > Phil
              >
              > --- In comets-ml@yahoogroups.com, jbortle@... wrote:
              >> I must say that the number of reliable, or in fact any sort of, magnitude
              >> determinations for this comet have been most disappointingly meager since
              >> it entered the northern hemisphere's skies. This situation is in dramatic
              >> contrast to the volume of southern hemisphere data that preceded perihelion.
              >> The lack of visual observations has been especially notable over the past
              >> week, or so, when almost nothing in the way of reports are apparent here, or
              >> in the CometObs file.
              >>
              >> I would, however, again like to caution those who do attempt visual
              >> photometric observations to employ an extra degree of care with C/2011 L4 so as
              >> not to integrate the beginnings of this comet's bright tail into their
              >> extra-focal comparisons. I feel a number may have done this recently. I viewed
              >> the comet last evening with large binoculars and noted the coma to be
              >> significantly fainter than might have been otherwise anticipated from some of
              >> last week's reported sighting by others. I would note that my comparison stars
              >> were also nearly at the same altitude as the comet, negating virtually any
              >> need for arbitrary extinction corrections to be appplied.
              >>
              >> Given that the coma appears all but star-like (only around 3'-4' in
              >> diameter) to the unaided eye and not in any way separate from the tail, I am
              >> particularly troubled by the apparent brightness of some of the reported
              >> determinations made without instrumentation.
              >>
              >> J.Bortle
              >>
              >>
              >>
              >>
              >> [Non-text portions of this message have been removed]
              >>
              >
              >
              >
              > ------------------------------------
              >
              > *** Comets Mailing List Important Contributions : ***
              > *** http://tech.groups.yahoo.com/group/comets-ml/files/Important%20Contributions/ ***
              >
              > Comet Observations List: http://groups.yahoo.com/group/CometObs/
              > Comet Images List: http://groups.yahoo.com/group/Comet-Images/
              >
              > NOTICE: Material quoted or re-posted from the Comets Mailing List should be indicated by:
              >
              > Comets Mailing List [date]
              > http://www.yahoogroups.com/group/comets-ml
              > Yahoo! Groups Links
              >
              >
              >
              >
              >
              > -----
              > No virus found in this message.
              > Checked by AVG - www.avg.com
              > Version: 2013.0.2904 / Virus Database: 2641/6203 - Release Date: 03/25/13


              [Non-text portions of this message have been removed]
            • Alan Hale
              Well, for what it s worth, the weather in this part of the world last week wasn t all that good either ‹ lots of clouds, plus windblown dust (this is the
              Message 6 of 17 , Mar 27, 2013
                Well, for what it's worth, the weather in this part of the world last week
                wasn't all that good either ‹ lots of clouds, plus windblown dust (this is
                the windy season here in NM) -- plus, I had a lot of social commitments last
                week that took up a lot of my evenings. And now, of course, the full moon
                (although the skies have been clear for the most part the past few nights).

                I did observe the comet Sunday evening under relatively good sky conditions,
                although obviously in a moon-brightened sky. March 25.10, m1=3.9 in 10x50
                binoculars; although I was able to use nearby stars as comparison objects,
                since the elevation is still low and even a couple of degrees can made a
                non-trivial difference in terms of extinction I still had to apply some
                correction for differential extinction. It's possible that the moonlight
                affected the magnitude measurement to some extent, but the comet is clearly
                quite a bit fainter than it was earlier this month.


                Sincerely,

                Alan





                [Non-text portions of this message have been removed]
              • Jakub Cerny
                As a central-Europe observer, I can say, that the reason, I am not able to do many magnitude estimates is overwhelming cruelty of weather here. My statistics
                Message 7 of 17 , Mar 27, 2013
                  As a central-Europe observer, I can say, that the reason, I am not able
                  to do many magnitude estimates is overwhelming cruelty of weather here.

                  My statistics are here:
                  From 10.3. to today (27.3.) there was:
                  - 7 evenings that there was a chance for clear sky in some part of my
                  country, we drive to comet between 100 to 400 km distance
                  - 3 evenings we succeed to catch the comet
                  - out of that 3 evenings, 2 there was cirruses interferring comet
                  - only 1 nights we were able to see comet on clear sky (unfortunately
                  there was low clouds covering tail that time)

                  now the forecast doesn't looks good in future 5 days already.

                  In contrast, during 2002 March I was able to observing comet Ikeya-Zhang
                  in 2 out of any 3 days without need to drive anywhere.

                  It looks that we totally missed this comet here due weather :(

                  Best regards,
                  Jakub Cerny,
                  Czech Republic


                  On 03/27/2013 02:16 PM, jbortle@... wrote:
                  >
                  > I must say that the number of reliable, or in fact any sort of, magnitude
                  > determinations for this comet have been most disappointingly meager since
                  > it entered the northern hemisphere's skies. This situation is in dramatic
                  > contrast to the volume of southern hemisphere data that preceded
                  > perihelion.
                  > The lack of visual observations has been especially notable over the past
                  > week, or so, when almost nothing in the way of reports are apparent
                  > here, or
                  > in the CometObs file.
                  >
                  > I would, however, again like to caution those who do attempt visual
                  > photometric observations to employ an extra degree of care with C/2011
                  > L4 so as
                  > not to integrate the beginnings of this comet's bright tail into their
                  > extra-focal comparisons. I feel a number may have done this recently.
                  > I viewed
                  > the comet last evening with large binoculars and noted the coma to be
                  > significantly fainter than might have been otherwise anticipated from
                  > some of
                  > last week's reported sighting by others. I would note that my
                  > comparison stars
                  > were also nearly at the same altitude as the comet, negating virtually
                  > any
                  > need for arbitrary extinction corrections to be appplied.
                  >
                  > Given that the coma appears all but star-like (only around 3'-4' in
                  > diameter) to the unaided eye and not in any way separate from the
                  > tail, I am
                  > particularly troubled by the apparent brightness of some of the reported
                  > determinations made without instrumentation.
                  >
                  > J.Bortle
                  >
                  >
                  >
                  >
                  > [Non-text portions of this message have been removed]
                  >
                  >



                  [Non-text portions of this message have been removed]
                • P. Clay Sherrod
                  Jakub and others are completely right here; the implication that observers are somehow ignoring this comet because of underperformance is grossly unfair. The
                  Message 8 of 17 , Mar 27, 2013
                    Jakub and others are completely right here; the implication that observers are
                    somehow ignoring this comet because of underperformance is grossly unfair.
                    The weather in the entire northern hemisphere (there are maps out there to
                    support this, not speculation) has been such that since the comet has entered
                    northern skies at such altitudes that it COULD be observed, it cannot be because
                    of obscuring clouds. Very simple. In many parts of North America there has
                    been a nightly trend for the past 3 weeks to have daytime clear followed by very
                    rapid development of evening clouds by dusk, only to clear after midnight.

                    We cannot dictate where the comet is: it is very near the western horizon at
                    dusk. We cannot ask for cooperation from the weather: the clouds are in the
                    same locations as the comet. Thus observers are unable to follow this comet at
                    this time.

                    I have nothing but admirations for our dedicated comet observers Down Under; but
                    frankly it appears that they were afforded far better observing conditions
                    during the time our comet spent in their neighborhoods. The coverage in the
                    southern hemisphere was phenomenal and on point.

                    Nothing conspirator, nothing biased.....I think that most observers of comets
                    would love to get their hands (or eyes/CCD) on PanStarrs right now.

                    Clay
                    _____
                    Dr. P. Clay Sherrod
                    Arkansas Sky Observatories
                    MPC H45 - Petit Jean Mountain South
                    MPC H41 - Petit Jean Mountain
                    MPC H43 - Conway West
                    http://www.arksky.org/

                    ----- Original Message -----
                    From: "Jakub Cerny" <kaos@...>
                    To: <comets-ml@yahoogroups.com>
                    Sent: Wednesday, March 27, 2013 1:32 PM
                    Subject: Re: [comets-ml] Comet 2011 L4, Where Are The Mag Estimates?


                    > As a central-Europe observer, I can say, that the reason, I am not able
                    > to do many magnitude estimates is overwhelming cruelty of weather here.
                    >
                    > My statistics are here:
                    > From 10.3. to today (27.3.) there was:
                    > - 7 evenings that there was a chance for clear sky in some part of my
                    > country, we drive to comet between 100 to 400 km distance
                    > - 3 evenings we succeed to catch the comet
                    > - out of that 3 evenings, 2 there was cirruses interferring comet
                    > - only 1 nights we were able to see comet on clear sky (unfortunately
                    > there was low clouds covering tail that time)
                    >
                    > now the forecast doesn't looks good in future 5 days already.
                    >
                    > In contrast, during 2002 March I was able to observing comet Ikeya-Zhang
                    > in 2 out of any 3 days without need to drive anywhere.
                    >
                    > It looks that we totally missed this comet here due weather :(
                    >
                    > Best regards,
                    > Jakub Cerny,
                    > Czech Republic
                    >
                    >
                    > On 03/27/2013 02:16 PM, jbortle@... wrote:
                    >>
                    >> I must say that the number of reliable, or in fact any sort of, magnitude
                    >> determinations for this comet have been most disappointingly meager since
                    >> it entered the northern hemisphere's skies. This situation is in dramatic
                    >> contrast to the volume of southern hemisphere data that preceded
                    >> perihelion.
                    >> The lack of visual observations has been especially notable over the past
                    >> week, or so, when almost nothing in the way of reports are apparent
                    >> here, or
                    >> in the CometObs file.
                    >>
                    >> I would, however, again like to caution those who do attempt visual
                    >> photometric observations to employ an extra degree of care with C/2011
                    >> L4 so as
                    >> not to integrate the beginnings of this comet's bright tail into their
                    >> extra-focal comparisons. I feel a number may have done this recently.
                    >> I viewed
                    >> the comet last evening with large binoculars and noted the coma to be
                    >> significantly fainter than might have been otherwise anticipated from
                    >> some of
                    >> last week's reported sighting by others. I would note that my
                    >> comparison stars
                    >> were also nearly at the same altitude as the comet, negating virtually
                    >> any
                    >> need for arbitrary extinction corrections to be appplied.
                    >>
                    >> Given that the coma appears all but star-like (only around 3'-4' in
                    >> diameter) to the unaided eye and not in any way separate from the
                    >> tail, I am
                    >> particularly troubled by the apparent brightness of some of the reported
                    >> determinations made without instrumentation.
                    >>
                    >> J.Bortle
                    >>
                    >>
                    >>
                    >>
                    >> [Non-text portions of this message have been removed]
                    >>
                    >>
                    >
                    >
                    >
                    > [Non-text portions of this message have been removed]
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    > *** Comets Mailing List Important Contributions : ***
                    > ***
                    > http://tech.groups.yahoo.com/group/comets-ml/files/Important%20Contributions/
                    > ***
                    >
                    > Comet Observations List: http://groups.yahoo.com/group/CometObs/
                    > Comet Images List: http://groups.yahoo.com/group/Comet-Images/
                    >
                    > NOTICE: Material quoted or re-posted from the Comets Mailing List should be
                    > indicated by:
                    >
                    > Comets Mailing List [date]
                    > http://www.yahoogroups.com/group/comets-ml
                    > Yahoo! Groups Links
                    >
                    >
                    >
                  • Toni Scarmato
                    Dear Jon and all, finally this evining I found the time to measure my last images of C/2011 L4 taken on my camera Canon 10D. Using Astroart I separated the 3
                    Message 9 of 17 , Mar 27, 2013
                      Dear Jon and all,
                      finally this evining I found the time to measure my last images of C/2011 L4 taken on my camera Canon 10D.
                      Using Astroart I separated the 3 bands RGB and measured the fluxs. In the FOV I found 4 stars to comparison!


                      DATE U.T. JD FluxS1 REF1 REF2 REF3 REF4 REF5 Magref pixels ° D (earth) R (sun) Rho (coma) JD Mag Comet JD Afrho CM bands
                      20130323 18:05:47 2456375,25374 226228 3666 2430 2416 1368 0 6,874 40 0,05444 1,20200 0,48600 171240 2456375,25374 3,474 2456375,25374 18218 R
                      20130323 18:05:47 2456375,25374 190431 3666 2430 2416 1368 0 6,994 40 0,05444 1,20200 0,48600 171240 2456375,25374 3,781 2456375,25374 13731 V
                      20130323 18:05:47 2456375,25374 169914 3666 2430 2416 1368 0 7,455 40 0,05444 1,20200 0,48600 171240 2456375,25374 4,366 2456375,25374 8013 B


                      The aperture used is 40 pixels that correspond at about 1 arcmin and it is important to note that with this aperture a little part of the tail is included in the flux.
                      At the same time visually using a 7x50 binoculars I estimed the comet
                      2013 Mar. 23.74 UT: m1=2.7*, Dia=5’, DC=7, 7x50B, Toni Scarmato (Calabria, Italy)
                      I think that it is clear that my visually estimation is affected to a large side of the tail due to the big aperture estimed of 5 arcmin vs 1 arcmin used in the image!
                      Probably I will be able to measure the extincion in terms of flux and so in magnitude using the 15x120 sec images.

                      So I agree with Jon that is totally right about the overestimations of visual nothern observers estimed aperture >2 arcmin!


                      regards,
                      Toni Scarmato

                      P.S note the very large value of Afrho!! Naturally actually I am no confidenze about the quality of this results!


                      [Non-text portions of this message have been removed]
                    • M.-T. Hui
                      Hi Jakub, You re not alone. Hadn t I made a special week-long-travel to somewhere around 1k km away from where I live, flying from SE China to SW China, I
                      Message 10 of 17 , Mar 27, 2013
                        Hi Jakub,

                        You're not alone. Hadn't I made a special week-long-travel to somewhere around 1k km away from where I live, flying from SE China to SW China, I wouldn't get any chance of seeing 2011 L4 whatsoever. The rainy season has come. I'm afraid when I make new rendezvous with the comet, it may already decline to an object of around 9-10 mag. :(

                        Cheers, Man-To
                        ------------------------------
                        On Thu, Mar 28, 2013 2:32 AM CST (China) Jakub Cerny wrote:

                        >As a central-Europe observer, I can say, that the reason, I am not able
                        >to do many magnitude estimates is overwhelming cruelty of weather here.
                        >
                        >My statistics are here:
                        > From 10.3. to today (27.3.) there was:
                        >- 7 evenings that there was a chance for clear sky in some part of my
                        >country, we drive to comet between 100 to 400 km distance
                        >- 3 evenings we succeed to catch the comet
                        >- out of that 3 evenings, 2 there was cirruses interferring comet
                        >- only 1 nights we were able to see comet on clear sky (unfortunately
                        >there was low clouds covering tail that time)
                        >
                        >now the forecast doesn't looks good in future 5 days already.
                        >
                        >In contrast, during 2002 March I was able to observing comet Ikeya-Zhang
                        >in 2 out of any 3 days without need to drive anywhere.
                        >
                        >It looks that we totally missed this comet here due weather :(
                        >
                        >Best regards,
                        >Jakub Cerny,
                        >Czech Republic
                        >
                        >
                        >On 03/27/2013 02:16 PM, jbortle@... wrote:
                        >>
                        >> I must say that the number of reliable, or in fact any sort of, magnitude
                        >> determinations for this comet have been most disappointingly meager since
                        >> it entered the northern hemisphere's skies. This situation is in dramatic
                        >> contrast to the volume of southern hemisphere data that preceded
                        >> perihelion.
                        >> The lack of visual observations has been especially notable over the past
                        >> week, or so, when almost nothing in the way of reports are apparent
                        >> here, or
                        >> in the CometObs file.
                        >>
                        >> I would, however, again like to caution those who do attempt visual
                        >> photometric observations to employ an extra degree of care with C/2011
                        >> L4 so as
                        >> not to integrate the beginnings of this comet's bright tail into their
                        >> extra-focal comparisons. I feel a number may have done this recently.
                        >> I viewed
                        >> the comet last evening with large binoculars and noted the coma to be
                        >> significantly fainter than might have been otherwise anticipated from
                        >> some of
                        >> last week's reported sighting by others. I would note that my
                        >> comparison stars
                        >> were also nearly at the same altitude as the comet, negating virtually
                        >> any
                        >> need for arbitrary extinction corrections to be appplied.
                        >>
                        >> Given that the coma appears all but star-like (only around 3'-4' in
                        >> diameter) to the unaided eye and not in any way separate from the
                        >> tail, I am
                        >> particularly troubled by the apparent brightness of some of the reported
                        >> determinations made without instrumentation.
                        >>
                        >> J.Bortle
                        >>
                        >>
                        >>
                        >>
                        >> [Non-text portions of this message have been removed]
                        >>
                        >>
                        >
                        >
                        >
                        >[Non-text portions of this message have been removed]
                        >
                      • terryjlovejoy
                        Actually the East Coast of Australia (where at least 50% of the population here lives) was almost totally clouded out for the entire evening display of
                        Message 11 of 17 , Mar 27, 2013
                          Actually the East Coast of Australia (where at least 50% of the population here lives) was almost totally clouded out for the entire evening display of PANSTARRS. Some parts of the east coast have already received their annual rainfall this year. Here in Brisbane I got 3 cloud effected observations over a 2 week period, and the only brief clear view of the comet I got was while it was raining!

                          Luckily the southern and western parts got some clear weather.

                          Terry
                        • José J. Chambó
                          From south-europe the weather is the same. In my case, since march 7 until 27 were 4 days clear at evening toward west horizon: In three I taken 3 images and
                          Message 12 of 17 , Mar 28, 2013
                            From south-europe the weather is the same. In my case, since march 7 until 27 were 4 days clear at evening toward west horizon: In three I taken 3 images and did one visual estimation, the other day I was busy and I couldn't.
                            I never saw so many clouds as these days...


                            Jos� J. Chamb� (Valencia, Spain)blog: cometografia.es twitter: @PepeChambo

                            To: comets-ml@yahoogroups.com
                            From: kaos@...
                            Date: Wed, 27 Mar 2013 19:32:32 +0100
                            Subject: Re: [comets-ml] Comet 2011 L4, Where Are The Mag Estimates?


























                            As a central-Europe observer, I can say, that the reason, I am not able

                            to do many magnitude estimates is overwhelming cruelty of weather here.



                            My statistics are here:

                            From 10.3. to today (27.3.) there was:

                            - 7 evenings that there was a chance for clear sky in some part of my

                            country, we drive to comet between 100 to 400 km distance

                            - 3 evenings we succeed to catch the comet

                            - out of that 3 evenings, 2 there was cirruses interferring comet

                            - only 1 nights we were able to see comet on clear sky (unfortunately

                            there was low clouds covering tail that time)



                            now the forecast doesn't looks good in future 5 days already.



                            In contrast, during 2002 March I was able to observing comet Ikeya-Zhang

                            in 2 out of any 3 days without need to drive anywhere.



                            It looks that we totally missed this comet here due weather :(



                            Best regards,

                            Jakub Cerny,

                            Czech Republic



                            On 03/27/2013 02:16 PM, jbortle@... wrote:

                            >

                            > I must say that the number of reliable, or in fact any sort of, magnitude

                            > determinations for this comet have been most disappointingly meager since

                            > it entered the northern hemisphere's skies. This situation is in dramatic

                            > contrast to the volume of southern hemisphere data that preceded

                            > perihelion.

                            > The lack of visual observations has been especially notable over the past

                            > week, or so, when almost nothing in the way of reports are apparent

                            > here, or

                            > in the CometObs file.

                            >

                            > I would, however, again like to caution those who do attempt visual

                            > photometric observations to employ an extra degree of care with C/2011

                            > L4 so as

                            > not to integrate the beginnings of this comet's bright tail into their

                            > extra-focal comparisons. I feel a number may have done this recently.

                            > I viewed

                            > the comet last evening with large binoculars and noted the coma to be

                            > significantly fainter than might have been otherwise anticipated from

                            > some of

                            > last week's reported sighting by others. I would note that my

                            > comparison stars

                            > were also nearly at the same altitude as the comet, negating virtually

                            > any

                            > need for arbitrary extinction corrections to be appplied.

                            >

                            > Given that the coma appears all but star-like (only around 3'-4' in

                            > diameter) to the unaided eye and not in any way separate from the

                            > tail, I am

                            > particularly troubled by the apparent brightness of some of the reported

                            > determinations made without instrumentation.

                            >

                            > J.Bortle

                            >

                            >

                            >

                            >

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

                            >

                            >



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


















                            [Non-text portions of this message have been removed]
                          • Juan Jose Gonzalez
                            John and friends, I haven t accessed the mail for some days, so here is my delayed contribution to these threads. March has been the rainiest month of recent
                            Message 13 of 17 , Mar 29, 2013
                              John and friends,

                              I haven't accessed the mail for some days, so here is my delayed
                              contribution to these threads.

                              March has been the rainiest month of recent years in N. Spain. I´ve
                              traveled about 3200 km seeking better skies for my C/2011 L4 estimates (
                              Mar. 10, 14, 17 and 20th ).

                              Weather permitting, I'll try to continue making a close follow-up of the
                              comet ...

                              Best regards and clear skies,


                              J. J. Gonzalez

                              ---------------------------------------------------------------------------------------------------------------
                            • Michael Boschat
                              I used 7x50 binoculars last night as it cleared unexpectedly and I de-focused the field. I observed the comet at about 0040 UT and had Delta Andromeda (3.4)
                              Message 14 of 17 , Mar 29, 2013
                                I used 7x50 binoculars last night as it cleared unexpectedly and I
                                de-focused
                                the field. I observed the comet at about 0040 UT and had Delta Andromeda
                                (3.4) and Pi Andromeda (4.3) in the field. To me the comet was fainter than
                                Delta and very close to Pi, I gave it a mag. of +4.0. I observed from
                                our apartment roof and there was lots of light pollution to be expected
                                from Halifax and the comet was in the direction of our container pier.
                                The tail was about 1/2 degrees long - to me.


                                Clear skies
                                -----------
                                Michael Boschat
                                Halifax Center- Royal Astronomical Society of Canada
                                web page: http://www.chebucto.ns.ca/~aa063
                              • Ellen Papenburg
                                Hmmm, I too find the estimates too generous , because with the best imagination I only m=4.4 the most (more like 4.5) on Friday (Sorry, that is 3:00 UT
                                Message 15 of 17 , Apr 1, 2013
                                  Hmmm, I too find the estimates too "generous", because with the best
                                  imagination I only m=4.4 the most (more like 4.5) on Friday (Sorry, that
                                  is 3:00 UT Saturday March 30) with the 15x70...

                                  So because I have a lower magnitude estimate than the rest of you I
                                  wonder... what methods are you all using? Haven't done this for a while
                                  so I might be "rusty", but you are supposed to use the same part of your
                                  retina and scope for looking at the comet and the two comparison stars
                                  basically all at about the same height in this case (lucky) and totally
                                  putting them quite a lot out of focus.

                                  So I wouldn't mind if our experts would shed some light on this.... for
                                  the sake of reaching as much accuracy as possible.

                                  We want to get this right!

                                  Thanks.

                                  Ellen - SW Ontario, Canada


                                  On 27/03/2013 9:16 AM, jbortle@... wrote:
                                  >
                                  > I must say that the number of reliable, or in fact any sort of, magnitude
                                  > determinations for this comet have been most disappointingly meager since
                                  > it entered the northern hemisphere's skies. This situation is in dramatic
                                  > contrast to the volume of southern hemisphere data that preceded
                                  > perihelion.
                                  > The lack of visual observations has been especially notable over the past
                                  > week, or so, when almost nothing in the way of reports are apparent
                                  > here, or
                                  > in the CometObs file.
                                  >
                                  > I would, however, again like to caution those who do attempt visual
                                  > photometric observations to employ an extra degree of care with C/2011
                                  > L4 so as
                                  > not to integrate the beginnings of this comet's bright tail into their
                                  > extra-focal comparisons. I feel a number may have done this recently.
                                  > I viewed
                                  > the comet last evening with large binoculars and noted the coma to be
                                  > significantly fainter than might have been otherwise anticipated from
                                  > some of
                                  > last week's reported sighting by others. I would note that my
                                  > comparison stars
                                  > were also nearly at the same altitude as the comet, negating virtually
                                  > any
                                  > need for arbitrary extinction corrections to be appplied.
                                  >
                                  > Given that the coma appears all but star-like (only around 3'-4' in
                                  > diameter) to the unaided eye and not in any way separate from the
                                  > tail, I am
                                  > particularly troubled by the apparent brightness of some of the reported
                                  > determinations made without instrumentation.
                                  >
                                  > J.Bortle
                                  >
                                  >
                                  >
                                  >
                                  > [Non-text portions of this message have been removed]
                                  >
                                  >



                                  [Non-text portions of this message have been removed]
                                • cnj999
                                  Ellen, I share your concern as, just like yourself, I have almost consistently obtained somewhat lower magnitudes than those reported by many other observers
                                  Message 16 of 17 , Apr 2, 2013
                                    Ellen, I share your concern as, just like yourself, I have almost consistently obtained somewhat lower magnitudes than those reported by many other observers in recent weeks.

                                    I note that I have been employing the traditional Sidgwick, or In-Out method only, as both the Bobrovnikoff and Beyer methods (the out-out and way-out methods) will result in the observer integrating the bright inner tail of the comet into the extra-focal image, producing an excessive brightness estimate for the comet.

                                    To obtain a correct magnitude determination for bright comets like c/2011 L4 the extra-focal image of the comparison stars must equal that of the coma's in-focus diameter as measured across its latus rectum. Incorporting anything more than that into the extra-focal image will give a false brightness value, particularly in the case of a bright-tailed comet. This I demonstrated in conjunction with Comet Hale-Bopp in the 1990's with a long series of photometric measures employing all the accepted comparison methods along with a ranges of apertures.

                                    With the very small coma diameter exhibited by Comet PanSTARRS together with its very bright inner tail, accurate brightness estimates can prove a difficult thing to accomplish when using binoculars and quite impossible with just the unaided eye. I think this has been the source of many of the seemingly eccessively bright estimates, particularly those made immediately following the comet's perihelion without instrumentation.

                                    J.Bortle



                                    --- In comets-ml@yahoogroups.com, Ellen Papenburg <ellen@...> wrote:
                                    >
                                    >
                                    > Hmmm, I too find the estimates too "generous", because with the best
                                    > imagination I only m=4.4 the most (more like 4.5) on Friday (Sorry, that
                                    > is 3:00 UT Saturday March 30) with the 15x70...
                                    >
                                    > So because I have a lower magnitude estimate than the rest of you I
                                    > wonder... what methods are you all using? Haven't done this for a while
                                    > so I might be "rusty", but you are supposed to use the same part of your
                                    > retina and scope for looking at the comet and the two comparison stars
                                    > basically all at about the same height in this case (lucky) and totally
                                    > putting them quite a lot out of focus.
                                    >
                                    > So I wouldn't mind if our experts would shed some light on this.... for
                                    > the sake of reaching as much accuracy as possible.
                                    >
                                    > We want to get this right!
                                    >
                                    > Thanks.
                                    >
                                    > Ellen - SW Ontario, Canada
                                    >
                                    >
                                    > On 27/03/2013 9:16 AM, jbortle@... wrote:
                                    > >
                                    > > I must say that the number of reliable, or in fact any sort of, magnitude
                                    > > determinations for this comet have been most disappointingly meager since
                                    > > it entered the northern hemisphere's skies. This situation is in dramatic
                                    > > contrast to the volume of southern hemisphere data that preceded
                                    > > perihelion.
                                    > > The lack of visual observations has been especially notable over the past
                                    > > week, or so, when almost nothing in the way of reports are apparent
                                    > > here, or
                                    > > in the CometObs file.
                                    > >
                                    > > I would, however, again like to caution those who do attempt visual
                                    > > photometric observations to employ an extra degree of care with C/2011
                                    > > L4 so as
                                    > > not to integrate the beginnings of this comet's bright tail into their
                                    > > extra-focal comparisons. I feel a number may have done this recently.
                                    > > I viewed
                                    > > the comet last evening with large binoculars and noted the coma to be
                                    > > significantly fainter than might have been otherwise anticipated from
                                    > > some of
                                    > > last week's reported sighting by others. I would note that my
                                    > > comparison stars
                                    > > were also nearly at the same altitude as the comet, negating virtually
                                    > > any
                                    > > need for arbitrary extinction corrections to be appplied.
                                    > >
                                    > > Given that the coma appears all but star-like (only around 3'-4' in
                                    > > diameter) to the unaided eye and not in any way separate from the
                                    > > tail, I am
                                    > > particularly troubled by the apparent brightness of some of the reported
                                    > > determinations made without instrumentation.
                                    > >
                                    > > J.Bortle
                                    > >
                                    > >
                                    > >
                                    > >
                                    > > [Non-text portions of this message have been removed]
                                    > >
                                    > >
                                    >
                                    >
                                    >
                                    > [Non-text portions of this message have been removed]
                                    >
                                  • biver_nicolas
                                    I also just follow Ellen and John Bortle s remarks about reported (too bright) magnitudes of C/2011 L4. From a not so perfect sky 50km from Paris I made it at
                                    Message 17 of 17 , Apr 4, 2013
                                      I also just follow Ellen and John Bortle's remarks about reported (too bright) magnitudes of C/2011 L4. From a not so perfect sky 50km from Paris I made it at 4.9 on april 1.8 (probably a bit biased by low transmission), but looking at the beginning of the tail it did look at least as bright as the core of M31... but of course this is not the coma. And generally we also like having a magnitude estimate that gives an idea of its outgassing activity while dust tail especially when composed of dust emitted several days before provides some additional brightness not really representative of the comet actual activity. (17P was an extreme case several weeks after its outburst when outgassing had severly decreased and we were seeing a dust tail face on).

                                      Nicolas
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