Loading ...
Sorry, an error occurred while loading the content.

Sungrazing comet visibility

Expand Messages
  • Phil
    The light curve of C/2006 P1 (McNaught) is certainly intriguing. I can t envision it maintaining such a high n value. That being said, and I know this is a
    Message 1 of 12 , Nov 1, 2006
    View Source
    • 0 Attachment
      The light curve of C/2006 P1 (McNaught) is certainly intriguing. I
      can't envision it maintaining such a high "n" value. That being said,
      and I know this is a hypothetical question, but...

      ...if a comet is within 15, 10, or 5 degrees of the sun, respectively,
      how bright would it have to be in order to be visible to the naked
      eye, assuming decent sky transparency?

      Clear Skies,
      Phil
    • cnj999
      ... Based on own my extensive experimentation, made during the early 1980 s, I can offer the following formula that generally predicts the daytime visibility
      Message 2 of 12 , Nov 1, 2006
      View Source
      • 0 Attachment
        --- In comets-ml@yahoogroups.com, "Phil" <pcreed4863@...> wrote:
        >
        > The light curve of C/2006 P1 (McNaught) is certainly intriguing. I
        > can't envision it maintaining such a high "n" value. That being said,
        > and I know this is a hypothetical question, but...
        >
        > ...if a comet is within 15, 10, or 5 degrees of the sun, respectively,
        > how bright would it have to be in order to be visible to the naked
        > eye, assuming decent sky transparency?
        >

        Based on own my extensive experimentation, made during the early
        1980's, I can offer the following formula that generally predicts the
        daytime visibility limits for Sungrazing comets using binoculars or a
        small telescope. My orginal paper, addressing this subject in detail,
        appeared in the ICQ many years ago. I don't off hand have the reference.

        The formula below is accurate for an instrument of 8cm aperture using
        20x, working with the Sun's disk obscured, and in very clear skies. The
        formula is only meant to be valid within 20 degrees of the Sun. The
        term "m" is the lower magnitude limit, while "E" is the object's solar
        elongation in degrees.

        m = -2.5 + 2 log E

        Although it is difficult to say with any accuracy, I would anticipate
        that nakedeye visibility would probably require the object to be
        several magnitudes brighter than for an instrument of 8cm aperture.

        I would also have to add that there is zero chance of C/2006P1 becoming
        a nakedeye, daylight object.

        JBortle
      • Dave Herald
        Consider Venus, mag -4.3. Can you see Venus with the naked eye at 5 deg elongation? Certainly not while the Sun is up! 10deg? - yes, with Sun below horizon....
        Message 3 of 12 , Nov 1, 2006
        View Source
        • 0 Attachment
          Consider Venus, mag -4.3. Can you see Venus with the naked eye at 5 deg
          elongation? Certainly not while the Sun is up! 10deg? - yes, with Sun below
          horizon....

          The other factor is how the light from the comet is distributed. Venus is (to
          the naked eye) a point source. Spread the light over an area equivalent to the
          size of the moon, and the surface brightness is _much_ less.

          Dave Herald
          Canberra, Australia


          ----- Original Message -----
          From: "Phil" <pcreed4863@...>
          To: <comets-ml@yahoogroups.com>
          Sent: Thursday, November 02, 2006 1:43 AM
          Subject: [comets-ml] Sungrazing comet visibility


          The light curve of C/2006 P1 (McNaught) is certainly intriguing. I
          can't envision it maintaining such a high "n" value. That being said,
          and I know this is a hypothetical question, but...

          ...if a comet is within 15, 10, or 5 degrees of the sun, respectively,
          how bright would it have to be in order to be visible to the naked
          eye, assuming decent sky transparency?

          Clear Skies,
          Phil




          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
        • Maciej Reszelski
          ... With all respect John, Maybe not zero but less than 5% :). I always use David Levy s sequence that comets are like cats :) unpredict. I do not observe
          Message 4 of 12 , Nov 1, 2006
          View Source
          • 0 Attachment
            >I would also have to add that there is zero chance of C/2006P1 becoming
            >a nakedeye, daylight object.


            With all respect John,

            Maybe not zero but less than 5% :). I always use David Levy's sequence
            that comets are like cats :) unpredict.

            I do not observe famous comet West but I readed some time ago Gary Kronk's
            note that forecasts put comet at 5 mag. On other hand comet Kohoutek was put
            at -8 or even -10 and what happend almost every from this list know.
            That's what the comets are famous for me. You really never know....


            Best regards,
            Maciej
          • cnj999
            ... deg ... Sun below ... Venus is (to ... equivalent to the ... An interesting point, also I think touched upon in my article, was how much more 18th and 19th
            Message 5 of 12 , Nov 1, 2006
            View Source
            • 0 Attachment
              --- In comets-ml@yahoogroups.com, "Dave Herald" <drherald@...> wrote:
              >
              > Consider Venus, mag -4.3. Can you see Venus with the naked eye at 5
              deg
              > elongation? Certainly not while the Sun is up! 10deg? - yes, with
              Sun below
              > horizon....
              >
              > The other factor is how the light from the comet is distributed.
              Venus is (to
              > the naked eye) a point source. Spread the light over an area
              equivalent to the
              > size of the moon, and the surface brightness is _much_ less.
              >
              > Dave Herald
              > Canberra, Australia
              >

              An interesting point, also I think touched upon in my article, was
              how much more 18th and 19th century astronomers could "see" when it
              came to difficult objects, compared to what amateur's today accept
              as "visible". It's indeed rather shocking.

              As I recall, the great 19th Harvard astronomer G.P.Bond, states in
              one of his books that the planet Venus is always visible to the
              unaided eye in daylight at Cambridge (MA) providing its elongation
              from the Sun is greater than 5 degrees. Near superior conjunction,
              its magnitude would only be around -3.5 . Astonishing to most today,
              perhaps, but true providing the sky is very clear. In fact, with
              binoculars and using suitable cautions, Venus can be followed to
              within just a dozen arc minutes of the solar limb!

              In addition, the apparent telescopic size of the typical sungrazer's
              visible head (as reported for say Ikeya-Seki and 1882II) shrinks to
              about 0.2' around the time of perihelion passage. Thus, it looks
              about the same size Venus does at superior conjunction. Needless to
              say, the brightness of a sungrazer's head is extremely concentrated
              near T, not at all spread out. Further, in the case of Comet West,
              its head was also less than 1' in diameter when I saw it during the
              daytime.

              JBortle
            • Greg Crinklaw
              ... You are comparing apples and oranges. An observation like Bond s is an example of an extreme case: it s the answer to the question, can Venus be seen in
              Message 6 of 12 , Nov 1, 2006
              View Source
              • 0 Attachment
                cnj999 wrote:
                > As I recall, the great 19th Harvard astronomer G.P.Bond, states in
                > one of his books that the planet Venus is always visible to the
                > unaided eye in daylight at Cambridge (MA) providing its elongation
                > from the Sun is greater than 5 degrees. Near superior conjunction,
                > its magnitude would only be around -3.5 . Astonishing to most today,
                > perhaps, but true providing the sky is very clear. In fact, with
                > binoculars and using suitable cautions, Venus can be followed to
                > within just a dozen arc minutes of the solar limb!

                You are comparing apples and oranges. An observation like Bond's is an
                example of an extreme case: it's the answer to the question, "can Venus
                be seen in daylight under the best possible conditions?"

                On the other hand, you are comparing this extreme to "populist"
                astronomy, which asks the very different question, "can a typical
                backyard amateur expect to see Venus in daylight under typical conditions?"

                I really don't see the point in comparing the two at all. And I know of
                some amateurs here out west that regularly make the same sort of extreme
                observations. Comparing to them would be something less curmudgeonly...

                I for one am less shocked by Bond's assertion than by the
                meaninglessness of such a poor comparison. ;-)

                Greg

                --
                Greg Crinklaw
                Astronomical Software Developer
                Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

                SkyTools Software for the Observer:
                http://www.skyhound.com/cs.html

                Skyhound Observing Pages:
                http://www.skyhound.com/sh/skyhound.html
              • cnj999
                ... in ... elongation ... conjunction, ... today, ... is an ... Venus ... conditions? ... know of ... extreme ... curmudgeonly... ... Extreme? By no means.
                Message 7 of 12 , Nov 1, 2006
                View Source
                • 0 Attachment
                  --- In comets-ml@yahoogroups.com, Greg Crinklaw <crinklaw@...> wrote:
                  >
                  > cnj999 wrote:
                  > > As I recall, the great 19th Harvard astronomer G.P.Bond, states
                  in
                  > > one of his books that the planet Venus is always visible to the
                  > > unaided eye in daylight at Cambridge (MA) providing its
                  elongation
                  > > from the Sun is greater than 5 degrees. Near superior
                  conjunction,
                  > > its magnitude would only be around -3.5 . Astonishing to most
                  today,
                  > > perhaps, but true providing the sky is very clear. In fact, with
                  > > binoculars and using suitable cautions, Venus can be followed to
                  > > within just a dozen arc minutes of the solar limb!
                  >
                  > You are comparing apples and oranges. An observation like Bond's
                  is an
                  > example of an extreme case: it's the answer to the question, "can
                  Venus
                  > be seen in daylight under the best possible conditions?"
                  >
                  > On the other hand, you are comparing this extreme to "populist"
                  > astronomy, which asks the very different question, "can a typical
                  > backyard amateur expect to see Venus in daylight under typical
                  conditions?"
                  >
                  > I really don't see the point in comparing the two at all. And I
                  know of
                  > some amateurs here out west that regularly make the same sort of
                  extreme
                  > observations. Comparing to them would be something less
                  curmudgeonly...
                  >
                  > I for one am less shocked by Bond's assertion than by the
                  > meaninglessness of such a poor comparison. ;-)
                  >

                  Extreme? By no means. Bond's comment is typical of hundreds of such
                  entries to be found. If you look through the literature you will find
                  that so-called extreme observations were utterly commonplace during
                  the 19th and made by observers of every kind. However, once
                  photography took astronomy by storm, the techniques and effort
                  neccessary to conduct such observations. They became considered
                  extreme observation in the 20th century only out of ignorance and the
                  myth that such thing couldn't be done. The appearance of Comet Ikeya-
                  Seki in 1965 changed that and for a time resulted in a rebirth of
                  near-Sun observation, particularly with regard to comets.
                  Unfortunately, for most observers today, this sort of observation has
                  once again become a lost art.

                  The observation of objects in very close proximity to the solar disk
                  can be accomplished by any average observer if they only bother to
                  learn how to safely go about it. I used to demonstrate how easy it
                  was in conjunction with my comet lectures years ago. Following the
                  presentation, to their astronishment, I would have audience members,
                  weather permitting, safely go outside and be able to picking out
                  Venus at very smaller elongations. Although few observers seem able
                  to do it currently, it really is only a matter of having the
                  observing knowledge, nothing exceptional is involved...even you might
                  be able to learn to do it! ;)

                  JBortle
                • Greg Crinklaw
                  ... I m sorry: you didn t understand what I said. But I m not going to argue about it. -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New
                  Message 8 of 12 , Nov 1, 2006
                  View Source
                  • 0 Attachment
                    cnj999 wrote:
                    > Extreme? By no means.

                    I'm sorry: you didn't understand what I said. But I'm not going to
                    argue about it.

                    --
                    Greg Crinklaw
                    Astronomical Software Developer
                    Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

                    SkyTools Software for the Observer:
                    http://www.skyhound.com/cs.html

                    Skyhound Observing Pages:
                    http://www.skyhound.com/sh/skyhound.html
                  • Phil
                    John, I am not that familiar with the specific observations of astronomers in prior centuries, but I may have a theory... ...that it WAS indeed much clearer.
                    Message 9 of 12 , Nov 1, 2006
                    View Source
                    • 0 Attachment
                      John,

                      I am not that familiar with the specific observations of astronomers
                      in prior centuries, but I may have a theory...

                      ...that it WAS indeed much clearer.

                      Pollution is a significant visual impediment. Until I did a project
                      for my local astronomy club, I didn't realize exactly how MUCH.

                      In the Eastern U.S., summertime visibility typically runs 25-30 miles.
                      This doesn't sound too bad until you realize that under natural
                      conditions, the visibility SHOULD be 90 miles. The latter figure is
                      comparable to typical visibility in the Desert Southwest!

                      Most of the visibility impairment in the Eastern U.S. is attributable
                      to sulfur dioxide emissions from older coal-fired power plants. (By
                      2010, SO2 concentrations in the Eastern U.S. should start to fall
                      sharply with the implementation of the Clean Air Interstate Rule)
                      Sulfate particles in humid environments grow to sizes that are
                      INSIDIOUSLY effective at scattering light, thus those hot, humid,
                      "air-that-you-can-wear" days are the haziest. A warm, humid
                      environment DOES NOT mean it should naturally be hazy. Otherwise,
                      Hawaii would have chronically-low visibility. For more on visibility
                      in the Eastern U.S., the VIEWS website is the best one I could find:

                      http://vista.cira.colostate.edu/views/

                      The sections on "spatial patterns" and "composition" for the Eastern
                      U.S. are most revealing. Let's just say the combined with the
                      cloudiness, light pollution, and haze, we Ohio stargazers aren't
                      exactly God's chosen people when it comes to our hobby.

                      More on pollution's effect on visibility can be found here:

                      http://www.epa.gov/oar/visibility/what.html

                      I don't mean to bore anybody about this topic, and maybe it's wildly
                      tangential to the subject at-hand, but the point is, the 18th and
                      early-19th centuries had a mere fraction of the pollution sources that
                      we have today. Based on what I researched for my astronomy club's
                      presentation, my assertion would be that the sky on a humid, 90-degree
                      day in an Eastern U.S. location in the early 1800s would look by
                      today's standards as if a master-blaster cold front had just come through.

                      Clear Skies to all,
                      Phillip J. Creed

                      --- In comets-ml@yahoogroups.com, "cnj999" <jbortle@...> wrote:
                      >
                      > An interesting point, also I think touched upon in my article, was
                      > how much more 18th and 19th century astronomers could "see" when it
                      > came to difficult objects, compared to what amateur's today accept
                      > as "visible". It's indeed rather shocking.
                      >
                      > As I recall, the great 19th Harvard astronomer G.P.Bond, states in
                      > one of his books that the planet Venus is always visible to the
                      > unaided eye in daylight at Cambridge (MA) providing its elongation
                      > from the Sun is greater than 5 degrees. Near superior conjunction,
                      > its magnitude would only be around -3.5 . Astonishing to most today,
                      > perhaps, but true providing the sky is very clear. In fact, with
                      > binoculars and using suitable cautions, Venus can be followed to
                      > within just a dozen arc minutes of the solar limb!
                      >
                      > JBortle
                      >
                    • GWMobile
                      There was a recent discovery channel show which said sunlight to the ground has gone down 25% since the 1920 s all over the earth due to pollution. So it would
                      Message 10 of 12 , Nov 1, 2006
                      View Source
                      • 0 Attachment
                        There was a recent discovery channel show which said sunlight to the
                        ground has gone down 25% since the 1920's all over the earth due to
                        pollution.
                        So it would have decreased the view up by the same amount.



                        On Wed, 1 Nov 2006 2:26 pm, Phil wrote:
                        > John,
                        >
                        > I am not that familiar with the specific observations of astronomers
                        > in prior centuries, but I may have a theory...
                        >
                        > ...that it WAS indeed much clearer.
                        >
                        > Pollution is a significant visual impediment. Until I did a project
                        > for my local astronomy club, I didn't realize exactly how MUCH.
                        >
                        > In the Eastern U.S., summertime visibility typically runs 25-30 miles.
                        > This doesn't sound too bad until you realize that under natural
                        > conditions, the visibility SHOULD be 90 miles. The latter figure is
                        > comparable to typical visibility in the Desert Southwest!
                        >
                        > Most of the visibility impairment in the Eastern U.S. is attributable
                        > to sulfur dioxide emissions from older coal-fired power plants. (By
                        > 2010, SO2 concentrations in the Eastern U.S. should start to fall
                        > sharply with the implementation of the Clean Air Interstate Rule)
                        > Sulfate particles in humid environments grow to sizes that are
                        > INSIDIOUSLY effective at scattering light, thus those hot, humid,
                        > "air-that-you-can-wear" days are the haziest. A warm, humid
                        > environment DOES NOT mean it should naturally be hazy. Otherwise,
                        > Hawaii would have chronically-low visibility. For more on visibility
                        > in the Eastern U.S., the VIEWS website is the best one I could find:
                        >
                        > http://vista.cira.colostate.edu/views/
                        >
                        > The sections on "spatial patterns" and "composition" for the Eastern
                        > U.S. are most revealing. Let's just say the combined with the
                        > cloudiness, light pollution, and haze, we Ohio stargazers aren't
                        > exactly God's chosen people when it comes to our hobby.
                        >
                        > More on pollution's effect on visibility can be found here:
                        >
                        > http://www.epa.gov/oar/visibility/what.html
                        >
                        > I don't mean to bore anybody about this topic, and maybe it's wildly
                        > tangential to the subject at-hand, but the point is, the 18th and
                        > early-19th centuries had a mere fraction of the pollution sources that
                        > we have today. Based on what I researched for my astronomy club's
                        > presentation, my assertion would be that the sky on a humid, 90-degree
                        > day in an Eastern U.S. location in the early 1800s would look by
                        > today's standards as if a master-blaster cold front had just come
                        > through.
                        >
                        > Clear Skies to all,
                        > Phillip J. Creed
                        >
                        > --- In comets-ml@yahoogroups.com, "cnj999" <jbortle@...> wrote:
                        >>
                        >> An interesting point, also I think touched upon in my article, was
                        >> how much more 18th and 19th century astronomers could "see" when it
                        >> came to difficult objects, compared to what amateur's today accept
                        >> as "visible". It's indeed rather shocking.
                        >>
                        >> As I recall, the great 19th Harvard astronomer G.P.Bond, states in
                        >> one of his books that the planet Venus is always visible to the
                        >> unaided eye in daylight at Cambridge (MA) providing its elongation
                        >> from the Sun is greater than 5 degrees. Near superior conjunction,
                        >> its magnitude would only be around -3.5 . Astonishing to most today,
                        >> perhaps, but true providing the sky is very clear. In fact, with
                        >> binoculars and using suitable cautions, Venus can be followed to
                        >> within just a dozen arc minutes of the solar limb!
                        >>
                        >> JBortle
                        >>
                        >
                        >
                        >
                        >
                        >
                        > 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
                        >
                        >
                        >
                        www.GlobalBoiling.com for daily updated facts about hurricanes,
                        globalwarming and the melting poles.

                        www.ElectricQuakes.com daily solar and earthquake data.
                      • Carey Johnson
                        ... And that s exactly why I like to observe Comets. My friends in the astronomy clubs I ve belonged to go out and look at the same Messier objects and NGC s,
                        Message 11 of 12 , Nov 2, 2006
                        View Source
                        • 0 Attachment
                          >From: "Maciej Reszelski" <macres@...>
                          >Reply-To: comets-ml@yahoogroups.com
                          >To: <comets-ml@yahoogroups.com>
                          >Subject: Re: [comets-ml] Re: Sungrazing comet visibility
                          >Date: Wed, 1 Nov 2006 18:00:55 +0100
                          >
                          >I always use David Levy's sequence
                          >that comets are like cats :) unpredict.
                          >
                          >That's what the comets are famous for me. You really never know....
                          >
                          >
                          >Best regards,
                          >Maciej
                          >

                          And that's exactly why I like to observe Comets.
                          My friends in the astronomy clubs I've belonged to go out and look at the
                          same Messier objects and NGC's, over and over again. I like to kid them
                          that it looks the same as the last time.
                          Some of the more serious observers like tracking down 17th magnitude Arp
                          objects, and only point thier big Dob's to a comet after I bring it to thier
                          attention.

                          I like looking at comets because they can look different from night to
                          night, and if they happen to pass near to a deep sky object, then Bonus!

                          I say, let the Comets take you on a tour of sky.

                          Carey

                          _________________________________________________________________
                          Get today's hot entertainment gossip
                          http://movies.msn.com/movies/hotgossip?icid=T002MSN03A07001
                        • cnj999
                          ... That the transparency of an 18th or 19th century sky was rather better than today s is undoubtely true. However, I think that in many instances the
                          Message 12 of 12 , Nov 2, 2006
                          View Source
                          • 0 Attachment
                            --- In comets-ml@yahoogroups.com, "Phil" <pcreed4863@...> wrote:
                            >
                            > John,
                            >
                            > I am not that familiar with the specific observations of astronomers
                            > in prior centuries, but I may have a theory...
                            >
                            > ...that it WAS indeed much clearer.
                            >

                            That the transparency of an 18th or 19th century sky was rather better
                            than today's is undoubtely true. However, I think that in many
                            instances the relative deterioration is highly exaggerated. I've seen
                            and read a number of presentation and papers regarding how serious the
                            atmospheric pollution has become. But, at the same time, the very fact
                            that I can today match the best observers of 19th century when it comes
                            to detecting objects in extreme proximity to the solar disk, makes it
                            clear that the obscuration can not be dramatically different. Likewise,
                            while I supposedly reside in an area considered to suffer from very
                            large amounts of airborne particulates (New York State), on any
                            reasonably clear day my ground visibility is 50 miles or better.
                            Viewing an object at significant elevation above the horizon should
                            encounter much less interference. Further, at such times any strong
                            solar areole often does not exceed 1-degree in extent. These factors
                            being so, conditions can't really be all that bad.

                            I honestly do believe that the lack of such extreme reported
                            observations in recent decades is simply the result of observers
                            considing them to be totally impossible out of hand and therefore
                            making not attempts whatever to determine what their respective limits
                            actually are.

                            JBortle
                          Your message has been successfully submitted and would be delivered to recipients shortly.