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Comet Holmes leading compresion wave

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  • debclltx
    Gotta be careful to not creat effects that don t exist, but my recent photo of Holmes when edited in Photoshop appears to show a leading compression wave and
    Message 1 of 19 , Oct 30, 2007
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      Gotta be careful to not creat effects that don't exist, but my recent photo of Holmes when
      edited in Photoshop appears to show a leading compression wave and then a pressure drop
      immediately behind it. This assumed that the comet is going to the right. Any comments?

      Don
    • anjal_sharma
      Don, My DSI LRGB image of Holmes taken on Nov 2 shows the same leading compression wave and pressure drop type effect too. I don t think it is an artifact.
      Message 2 of 19 , Nov 5, 2007
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        Don,

        My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
        compression wave and pressure drop type effect too. I don't think it
        is an artifact.

        Anjal.

        --- In brazosastro@yahoogroups.com, "debclltx" <debray1@...> wrote:
        >
        > Gotta be careful to not creat effects that don't exist, but my recent
        photo of Holmes when
        > edited in Photoshop appears to show a leading compression wave and
        then a pressure drop
        > immediately behind it. This assumed that the comet is going to the
        right. Any comments?
        >
        > Don
        >
      • anjal_sharma
        Don, My DSI LRGB image of Holmes taken on Nov 2 shows the same leading compression wave and pressure drop type effect too. I don t think it is an artifact.
        Message 3 of 19 , Nov 5, 2007
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          Don,

          My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
          compression wave and pressure drop type effect too. I don't think it
          is an artifact.

          Anjal.

          --- In brazosastro@yahoogroups.com, "debclltx" <debray1@...> wrote:
          >
          > Gotta be careful to not creat effects that don't exist, but my recent
          photo of Holmes when
          > edited in Photoshop appears to show a leading compression wave and
          then a pressure drop
          > immediately behind it. This assumed that the comet is going to the
          right. Any comments?
          >
          > Don
          >
        • Don E. Bray
          Anjal et al., It also shows up in Mark s photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever
          Message 4 of 19 , Nov 6, 2007
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            Anjal et al.,

            It also shows up in Mark's photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever atmosphere it is encountering. Been a few years since I did fluid flow work related to projectiles, but the leading compressional wave and then a drop off is consistent with other photos that I have seen in bullet and airplane wind tunnel shots. So, it must be physically there. Also, one could deduce something about the properties of the atmosphere that it is encountering by measuring the spacing between light and dark areas and the comet body. But, I expect that real astrophysicists have already done that.

            Note that it does not show up in the other photos, at least it is not as obvious. This is possible due to Photoshop processing. But these photos where the compression wave is not shown emphasize the actual solid body of the comet, so they are all part of a complete information package.

            Thanks, for your comment. This is all very interesting.

            Don

            On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:

            Don,

            My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
            compression wave and pressure drop type effect too. I don't think it
            is an artifact.

            Anjal.

            --- In brazosastro@yahoogroups.com, "debclltx" <debray1@...> wrote:
            >
            > Gotta be careful to not creat effects that don't exist, but my recent
            photo of Holmes when
            > edited in Photoshop appears to show a leading compression wave and
            then a pressure drop
            > immediately behind it. This assumed that the comet is going to the
            right. Any comments?
            >
            > Don
            >


            **** Note change in telephone numbers ****
            Don E. Bray, Ph.D., P. E.
            Don E. Bray, Inc.
            Mail P. O. Box 10315, College Station, Texas 77842-0315
            Ship 1601 Fontaine Street, College Station, Texas 77845-5612
            USA
            Office/Cellular 979-492-9534
            Fax 979-693-1620
            Res 979-693-1620
            Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html

          • anjal_sharma@yahoo.com
            Have y all seen this really long exposure image of Holmes on Astronomy Picture of the day website? http://antwrp.gsfc.nasa.gov/apod/ap071105.html It s superb.
            Message 5 of 19 , Nov 6, 2007
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              Have y'all seen this really long exposure image of Holmes on Astronomy Picture of the day website? 

              http://antwrp.gsfc.nasa.gov/apod/ap071105.html

              It's superb.  Looks like all the images posted here by group members are relatively short exposures and only show the inner region of the comet.  This guy has gone much deeper with his image and it clearly shows the outer regions and what appears to be a tail behind the comet.  Check it out.

              ----- Original Message ----
              From: Don E. Bray <debray1@...>
              To: brazosastro@yahoogroups.com
              Sent: Tuesday, November 6, 2007 8:42:52 AM
              Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave

              Anjal et al.,


              It also shows up in Mark's photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever atmosphere it is encountering. Been a few years since I did fluid flow work related to projectiles, but the leading compressional wave and then a drop off is consistent with other photos that I have seen in bullet and airplane wind tunnel shots. So, it must be physically there. Also, one could deduce something about the properties of the atmosphere that it is encountering by measuring the spacing between light and dark areas and the comet body. But, I expect that real astrophysicists have already done that.

              Note that it does not show up in the other photos, at least it is not as obvious. This is possible due to Photoshop processing. But these photos where the compression wave is not shown emphasize the actual solid body of the comet, so they are all part of a complete information package.

              Thanks, for your comment. This is all very interesting.

              Don

              On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:

              Don,

              My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
              compression wave and pressure drop type effect too. I don't think it
              is an artifact.

              Anjal.

              --- In brazosastro@yahoogroups.com, "debclltx" <debray1@...> wrote:
              >
              > Gotta be careful to not creat effects that don't exist, but my recent
              photo of Holmes when
              > edited in Photoshop appears to show a leading compression wave and
              then a pressure drop
              > immediately behind it. This assumed that the comet is going to the
              right. Any comments?
              >
              > Don
              >


              **** Note change in telephone numbers ****
              Don E. Bray, Ph.D., P. E.
              Don E. Bray, Inc.
              Mail P. O. Box 10315, College Station, Texas 77842-0315
              Ship 1601 Fontaine Street, College Station, Texas 77845-5612
              USA
              Office/Cellular 979-492-9534
              Fax 979-693-1620
              Res 979-693-1620
              Astronomy photos http://homepage. mac.com/debray1/ PhotoAlbum22. html



              __________________________________________________
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            • Don E. Bray
              Very good. Thanks, Don ... **** Note change in telephone numbers **** Don E. Bray, Ph.D., P. E. Don E. Bray, Inc. Mail P. O. Box 10315, College Station, Texas
              Message 6 of 19 , Nov 6, 2007
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                Very good. Thanks,

                Don

                On 6 Nov 2007, at 8:55 AM, anjal_sharma@... wrote:


                Have y'all seen this really long exposure image of Holmes on Astronomy Picture of the day website? 

                http://antwrp.gsfc.nasa.gov/apod/ap071105.html

                It's superb.  Looks like all the images posted here by group members are relatively short exposures and only show the inner region of the comet.  This guy has gone much deeper with his image and it clearly shows the outer regions and what appears to be a tail behind the comet.  Check it out.

                ----- Original Message ----
                From: Don E. Bray <debray1@mac.com>
                To: brazosastro@yahoogroups.com
                Sent: Tuesday, November 6, 2007 8:42:52 AM
                Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave

                Anjal et al.,


                It also shows up in Mark's photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever atmosphere it is encountering. Been a few years since I did fluid flow work related to projectiles, but the leading compressional wave and then a drop off is consistent with other photos that I have seen in bullet and airplane wind tunnel shots. So, it must be physically there. Also, one could deduce something about the properties of the atmosphere that it is encountering by measuring the spacing between light and dark areas and the comet body. But, I expect that real astrophysicists have already done that.

                Note that it does not show up in the other photos, at least it is not as obvious. This is possible due to Photoshop processing. But these photos where the compression wave is not shown emphasize the actual solid body of the comet, so they are all part of a complete information package.

                Thanks, for your comment. This is all very interesting.

                Don

                On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:

                Don,

                My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                compression wave and pressure drop type effect too. I don't think it
                is an artifact.

                Anjal.

                --- In brazosastro@yahoogroups.com, "debclltx" <debray1@...> wrote:
                >
                > Gotta be careful to not creat effects that don't exist, but my recent
                photo of Holmes when
                > edited in Photoshop appears to show a leading compression wave and
                then a pressure drop
                > immediately behind it. This assumed that the comet is going to the
                right. Any comments?
                >
                > Don
                >


                **** Note change in telephone numbers ****
                Don E. Bray, Ph.D., P. E.
                Don E. Bray, Inc.
                Mail P. O. Box 10315, College Station, Texas 77842-0315
                Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                USA
                Office/Cellular 979-492-9534
                Fax 979-693-1620
                Res 979-693-1620
                Astronomy photos http://homepage. mac.com/debray1/ PhotoAlbum22. html



                __________________________________________________
                Do You Yahoo!?
                Tired of spam? Yahoo! Mail has the best spam protection around
                http://mail.yahoo.com


                **** Note change in telephone numbers ****
                Don E. Bray, Ph.D., P. E.
                Don E. Bray, Inc.
                Mail P. O. Box 10315, College Station, Texas 77842-0315
                Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                USA
                Office/Cellular 979-492-9534
                Fax 979-693-1620
                Res 979-693-1620
                Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html

              • Kelsey Golden
                Don and Anjal, I just put up my latest LRGB image of Holmes which was also taken on 11/02. I m kind of new to RGB processing and mine came out a much
                Message 7 of 19 , Nov 6, 2007
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                  Don and Anjal,

                  I just put up my latest LRGB image of Holmes which was also taken on 11/02. I'm kind of new to RGB processing and mine came out a much differen't color than most of the images of Holmes that I've seen. Either the focus or the exposure of the luminosity channel could've used some adjustment as well. At any rate, you can see the same issues as you describe in my photo as well.

                  Kelsey

                  On 11/6/07, Don E. Bray <debray1@...> wrote:

                  Anjal et al.,


                  It also shows up in Mark's photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever atmosphere it is encountering. Been a few years since I did fluid flow work related to projectiles, but the leading compressional wave and then a drop off is consistent with other photos that I have seen in bullet and airplane wind tunnel shots. So, it must be physically there. Also, one could deduce something about the properties of the atmosphere that it is encountering by measuring the spacing between light and dark areas and the comet body. But, I expect that real astrophysicists have already done that.

                  Note that it does not show up in the other photos, at least it is not as obvious. This is possible due to Photoshop processing. But these photos where the compression wave is not shown emphasize the actual solid body of the comet, so they are all part of a complete information package.

                  Thanks, for your comment. This is all very interesting.

                  Don

                  On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:

                  Don,

                  My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                  compression wave and pressure drop type effect too. I don't think it
                  is an artifact.

                  Anjal.

                  --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                  >
                  > Gotta be careful to not creat effects that don't exist, but my recent
                  photo of Holmes when
                  > edited in Photoshop appears to show a leading compression wave and
                  then a pressure drop
                  > immediately behind it. This assumed that the comet is going to the
                  right. Any comments?
                  >
                  > Don
                  >


                  **** Note change in telephone numbers ****
                  Don E. Bray, Ph.D., P. E.
                  Don E. Bray, Inc.
                  Mail P. O. Box 10315, College Station, Texas 77842-0315
                  Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                  USA
                  Office/Cellular 979-492-9534
                  Fax 979-693-1620
                  Res 979-693-1620
                  Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html


                • Don E. Bray
                  Kelsey, You are right, it is there. The difference in image density is subtle, but if you look at it correctly, that outward leading front is unmistakably
                  Message 8 of 19 , Nov 6, 2007
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                    Kelsey,

                    You are right, it is there. The difference in image density is subtle, but if you look at it correctly, that outward leading front is unmistakably there.

                    Good work.

                    Don

                    On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:

                    Don and Anjal,

                    I just put up my latest LRGB image of Holmes which was also taken on 11/02. I'm kind of new to RGB processing and mine came out a much differen't color than most of the images of Holmes that I've seen. Either the focus or the exposure of the luminosity channel could've used some adjustment as well. At any rate, you can see the same issues as you describe in my photo as well.

                    Kelsey

                    On 11/6/07, Don E. Bray <debray1@mac.com> wrote:

                    Anjal et al.,


                    It also shows up in Mark's photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever atmosphere it is encountering. Been a few years since I did fluid flow work related to projectiles, but the leading compressional wave and then a drop off is consistent with other photos that I have seen in bullet and airplane wind tunnel shots. So, it must be physically there. Also, one could deduce something about the properties of the atmosphere that it is encountering by measuring the spacing between light and dark areas and the comet body. But, I expect that real astrophysicists have already done that.

                    Note that it does not show up in the other photos, at least it is not as obvious. This is possible due to Photoshop processing. But these photos where the compression wave is not shown emphasize the actual solid body of the comet, so they are all part of a complete information package.

                    Thanks, for your comment. This is all very interesting.

                    Don

                    On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:

                    Don,

                    My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                    compression wave and pressure drop type effect too. I don't think it
                    is an artifact.

                    Anjal.

                    --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                    >
                    > Gotta be careful to not creat effects that don't exist, but my recent
                    photo of Holmes when
                    > edited in Photoshop appears to show a leading compression wave and
                    then a pressure drop
                    > immediately behind it. This assumed that the comet is going to the
                    right. Any comments?
                    >
                    > Don
                    >



                    **** Note change in telephone numbers ****
                    Don E. Bray, Ph.D., P. E.
                    Don E. Bray, Inc.
                    Mail P. O. Box 10315, College Station, Texas 77842-0315
                    Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                    USA
                    Office/Cellular 979-492-9534
                    Fax 979-693-1620
                    Res 979-693-1620
                    Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html




                    **** Note change in telephone numbers ****
                    Don E. Bray, Ph.D., P. E.
                    Don E. Bray, Inc.
                    Mail P. O. Box 10315, College Station, Texas 77842-0315
                    Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                    USA
                    Office/Cellular 979-492-9534
                    Fax 979-693-1620
                    Res 979-693-1620
                    Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html

                  • anjal_sharma@yahoo.com
                    Kelsey, Did you adjust the color weights on the R, G and B channels? You have to do this to account for different spectral transmission areas by the filters
                    Message 9 of 19 , Nov 6, 2007
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                      Kelsey,

                      Did you adjust the color weights on the R, G and B channels?  You have to do this to account for different spectral transmission areas by the filters at the three primary colors and also for some spectral overlap between the B and G filters and a gap in the spectrum between the G and R filters.  Here's an attachment which shows how the L R G abd B filters in your Meade filter set behave.  You can get a good guess as to color weight by using these spectra. 

                      Also note the native spectra of the G and R filters.  They let in SIGNIFICANT amounts of IR light.  Note also the native spectrum of the B filter.  It lets in SIGNIFICANT amounts of UV light.  Although not a problem with your reflector, your ED80 and my Sky90 are apochromats and not super-apochromats.  They cannot focus the UV and IR light at the same point as visible wavelengths.

                      Therefore, unless you screw in the L filter which is the IR block filter in the nosepiece of your DSI camera which is sensitive well into the UV and IR, you're going to get slightly bloated stars in the LRGB image and perhaps a bit of residual chroma as these UV and IR wavelengths will mix in with the B, G and R wavelengths. 

                      Anjal.

                      ----- Original Message ----
                      From: Don E. Bray <debray1@...>
                      To: brazosastro@yahoogroups.com
                      Sent: Tuesday, November 6, 2007 2:59:18 PM
                      Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave

                      Kelsey,


                      You are right, it is there. The difference in image density is subtle, but if you look at it correctly, that outward leading front is unmistakably there.

                      Good work.

                      Don

                      On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:

                      Don and Anjal,

                      I just put up my latest LRGB image of Holmes which was also taken on 11/02. I'm kind of new to RGB processing and mine came out a much differen't color than most of the images of Holmes that I've seen. Either the focus or the exposure of the luminosity channel could've used some adjustment as well. At any rate, you can see the same issues as you describe in my photo as well.

                      Kelsey

                      On 11/6/07, Don E. Bray <debray1@mac.com> wrote:

                      Anjal et al.,


                      It also shows up in Mark's photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever atmosphere it is encountering. Been a few years since I did fluid flow work related to projectiles, but the leading compressional wave and then a drop off is consistent with other photos that I have seen in bullet and airplane wind tunnel shots. So, it must be physically there. Also, one could deduce something about the properties of the atmosphere that it is encountering by measuring the spacing between light and dark areas and the comet body. But, I expect that real astrophysicists have already done that.

                      Note that it does not show up in the other photos, at least it is not as obvious. This is possible due to Photoshop processing. But these photos where the compression wave is not shown emphasize the actual solid body of the comet, so they are all part of a complete information package.

                      Thanks, for your comment. This is all very interesting.

                      Don

                      On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:

                      Don,

                      My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                      compression wave and pressure drop type effect too. I don't think it
                      is an artifact.

                      Anjal.

                      --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                      >
                      > Gotta be careful to not creat effects that don't exist, but my recent
                      photo of Holmes when
                      > edited in Photoshop appears to show a leading compression wave and
                      then a pressure drop
                      > immediately behind it. This assumed that the comet is going to the
                      right. Any comments?
                      >
                      > Don
                      >



                      **** Note change in telephone numbers ****
                      Don E. Bray, Ph.D., P. E.
                      Don E. Bray, Inc.
                      Mail P. O. Box 10315, College Station, Texas 77842-0315
                      Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                      USA
                      Office/Cellular 979-492-9534
                      Fax 979-693-1620
                      Res 979-693-1620
                      Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html




                      **** Note change in telephone numbers ****
                      Don E. Bray, Ph.D., P. E.
                      Don E. Bray, Inc.
                      Mail P. O. Box 10315, College Station, Texas 77842-0315
                      Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                      USA
                      Office/Cellular 979-492-9534
                      Fax 979-693-1620
                      Res 979-693-1620
                      Astronomy photos http://homepage. mac.com/debray1/ PhotoAlbum22. html



                      __________________________________________________
                      Do You Yahoo!?
                      Tired of spam? Yahoo! Mail has the best spam protection around
                      http://mail.yahoo.com
                    • Kelsey Golden
                      I didn t adjust the weights at all. I copied each filtered black and white image (unedited) into the corresponding R, G, and B channel of the image which is
                      Message 10 of 19 , Nov 6, 2007
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                        I didn't adjust the weights at all. I copied each filtered black and
                        white image (unedited) into the corresponding R, G, and B channel of
                        the image which is something you can do in the "channels" tab of the
                        layers window in photo shop. I then made an additional layer with
                        properties set to "luminosity" which housed the luminosity filter
                        image... at least I thought the L filter was in when I took it.

                        I will try your method and see what happens although i believe that
                        using the RGB channels tool in photoshop is a bit easier than
                        colorizing each image before combining.

                        Kelsey

                        On Nov 6, 2007 3:20 PM, <anjal_sharma@...> wrote:
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        > Kelsey,
                        >
                        > Did you adjust the color weights on the R, G and B channels? You have to do
                        > this to account for different spectral transmission areas by the filters at
                        > the three primary colors and also for some spectral overlap between the B
                        > and G filters and a gap in the spectrum between the G and R filters. Here's
                        > an attachment which shows how the L R G abd B filters in your Meade filter
                        > set behave. You can get a good guess as to color weight by using these
                        > spectra.
                        >
                        > Also note the native spectra of the G and R filters. They let in
                        > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                        > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                        > with your reflector, your ED80 and my Sky90 are apochromats and not
                        > super-apochromats. They cannot focus the UV and IR light at the same point
                        > as visible wavelengths.
                        >
                        > Therefore, unless you screw in the L filter which is the IR block filter in
                        > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                        > you're going to get slightly bloated stars in the LRGB image and perhaps a
                        > bit of residual chroma as these UV and IR wavelengths will mix in with the
                        > B, G and R wavelengths.
                        >
                        > Anjal.
                        >
                        >
                        > ----- Original Message ----
                        > From: Don E. Bray <debray1@...>
                        > To: brazosastro@yahoogroups.com
                        > Sent: Tuesday, November 6, 2007 2:59:18 PM
                        > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                        >
                        >
                        >
                        >
                        >
                        > Kelsey,
                        >
                        > You are right, it is there. The difference in image density is subtle, but
                        > if you look at it correctly, that outward leading front is unmistakably
                        > there.
                        >
                        > Good work.
                        >
                        > Don
                        >
                        >
                        > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                        >
                        >
                        >
                        >
                        > Don and Anjal,
                        >
                        > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                        > I'm kind of new to RGB processing and mine came out a much differen't color
                        > than most of the images of Holmes that I've seen. Either the focus or the
                        > exposure of the luminosity channel could've used some adjustment as well. At
                        > any rate, you can see the same issues as you describe in my photo as well.
                        >
                        > Kelsey
                        >
                        > On 11/6/07, Don E. Bray <debray1@...> wrote:
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > Anjal et al.,
                        > >
                        > >
                        > > It also shows up in Mark's photo, but not in the others. The physical
                        > effect is most likely due to the flow of this projectile in the whatever
                        > atmosphere it is encountering. Been a few years since I did fluid flow work
                        > related to projectiles, but the leading compressional wave and then a drop
                        > off is consistent with other photos that I have seen in bullet and airplane
                        > wind tunnel shots. So, it must be physically there. Also, one could deduce
                        > something about the properties of the atmosphere that it is encountering by
                        > measuring the spacing between light and dark areas and the comet body. But,
                        > I expect that real astrophysicists have already done that.
                        > >
                        > >
                        > > Note that it does not show up in the other photos, at least it is not as
                        > obvious. This is possible due to Photoshop processing. But these photos
                        > where the compression wave is not shown emphasize the actual solid body of
                        > the comet, so they are all part of a complete information package.
                        > >
                        > >
                        > > Thanks, for your comment. This is all very interesting.
                        > >
                        > >
                        > > Don
                        > >
                        > >
                        > >
                        > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > Don,
                        > >
                        > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                        > > compression wave and pressure drop type effect too. I don't think it
                        > > is an artifact.
                        > >
                        > > Anjal.
                        > >
                        > > --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                        > > >
                        > > > Gotta be careful to not creat effects that don't exist, but my recent
                        > > photo of Holmes when
                        > > > edited in Photoshop appears to show a leading compression wave and
                        > > then a pressure drop
                        > > > immediately behind it. This assumed that the comet is going to the
                        > > right. Any comments?
                        > > >
                        > > > Don
                        > > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > **** Note change in telephone numbers ****
                        > > Don E. Bray, Ph.D., P. E.
                        > > Don E. Bray, Inc.
                        > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                        > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                        > > USA
                        > > Office/Cellular 979-492-9534
                        > > Fax 979-693-1620
                        > > Res 979-693-1620
                        > > debray1@...
                        > > debray1@...
                        > > < http://brayengr.com>Astronomy photos
                        > http://homepage.mac.com/debray1/PhotoAlbum22.html
                        > >
                        > >
                        >
                        >
                        >
                        >
                        > **** Note change in telephone numbers ****
                        > Don E. Bray, Ph.D., P. E.
                        > Don E. Bray, Inc.
                        > Mail P. O. Box 10315, College Station, Texas 77842-0315
                        > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                        > USA
                        > Office/Cellular 979-492-9534
                        > Fax 979-693-1620
                        > Res 979-693-1620
                        > debray1@mac. com
                        > debray1@brayengr. com
                        > <http://brayengr. com>Astronomy photos http://homepage. mac.com/debray1/
                        > PhotoAlbum22. html
                        >
                        >
                        >
                        > __________________________________________________
                        > Do You Yahoo!?
                        > Tired of spam? Yahoo! Mail has the best spam protection around
                        > http://mail.yahoo.com
                        >
                      • anjal_sharma@yahoo.com
                        Hi Kelsey, What version of Photoshop are you using? I have a really old version (PS 5.0LE) which doesn t have the ability to do discrete channels in the
                        Message 11 of 19 , Nov 7, 2007
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                          Hi Kelsey,

                          What version of Photoshop are you using?  I have a really old version (PS 5.0LE) which doesn't have the ability to do discrete channels in the layers menu item.  I use  Meade's Image Processing subprogram in Autostar Suite to do the RGB conversion from the individual R G and B images saved as FITS files (won't work with JPEGs). Alternatively I have in the past done colorized images in my copy of PS, but you're right....it is a tedious process. 

                          Was your Luminosity filter screwed in to the nosepiece? For the best results the R, G and B filters should be in the filter slide bar while the L filter should be in the nosepiece to ensure that you cut off UV and IR light from entering the sensor for all images.

                          BTW, I've been meaning to do narrowband imaging for some time now.  I have a set of H-alpha, OIII, H-beta and SII filters for the job, but I've not made a serious effort thus far.  How about we try narrowband imaging sometime this week?  Let me know what your schedule is like.

                          Anjal.


                          ----- Original Message ----
                          From: Kelsey Golden <kcgolden@...>
                          To: brazosastro@yahoogroups.com
                          Sent: Tuesday, November 6, 2007 10:32:15 PM
                          Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave

                          I didn't adjust the weights at all. I copied each filtered black and
                          white image (unedited) into the corresponding R, G, and B channel of
                          the image which is something you can do in the "channels" tab of the
                          layers window in photo shop. I then made an additional layer with
                          properties set to "luminosity" which housed the luminosity filter
                          image... at least I thought the L filter was in when I took it.

                          I will try your method and see what happens although i believe that
                          using the RGB channels tool in photoshop is a bit easier than
                          colorizing each image before combining.

                          Kelsey

                          On Nov 6, 2007 3:20 PM, <anjal_sharma@ yahoo.com> wrote:
                          >
                          >
                          >
                          >
                          >
                          >
                          >
                          > Kelsey,
                          >
                          > Did you adjust the color weights on the R, G and B channels? You have to do
                          > this to account for different spectral transmission areas by the filters at
                          > the three primary colors and also for some spectral overlap between the B
                          > and G filters and a gap in the spectrum between the G and R filters. Here's
                          > an attachment which shows how the L R G abd B filters in your Meade filter
                          > set behave. You can get a good guess as to color weight by using these
                          > spectra.
                          >
                          > Also note the native spectra of the G and R filters. They let in
                          > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                          > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                          > with your reflector, your ED80 and my Sky90 are apochromats and not
                          > super-apochromats. They cannot focus the UV and IR light at the same point
                          > as visible wavelengths.
                          >
                          > Therefore, unless you screw in the L filter which is the IR block filter in
                          > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                          > you're going to get slightly bloated stars in the LRGB image and perhaps a
                          > bit of residual chroma as these UV and IR wavelengths will mix in with the
                          > B, G and R wavelengths.
                          >
                          > Anjal.
                          >
                          >
                          > ----- Original Message ----
                          > From: Don E. Bray <debray1@mac. com>
                          > To: brazosastro@ yahoogroups. com
                          > Sent: Tuesday, November 6, 2007 2:59:18 PM
                          > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                          >
                          >
                          >
                          >
                          >
                          > Kelsey,
                          >
                          > You are right, it is there. The difference in image density is subtle, but
                          > if you look at it correctly, that outward leading front is unmistakably
                          > there.
                          >
                          > Good work.
                          >
                          > Don
                          >
                          >
                          > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                          >
                          >
                          >
                          >
                          > Don and Anjal,
                          >
                          > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                          > I'm kind of new to RGB processing and mine came out a much differen't color
                          > than most of the images of Holmes that I've seen. Either the focus or the
                          > exposure of the luminosity channel could've used some adjustment as well. At
                          > any rate, you can see the same issues as you describe in my photo as well.
                          >
                          > Kelsey
                          >
                          > On 11/6/07, Don E. Bray <debray1@mac. com> wrote:
                          > >
                          > >
                          > >
                          > >
                          > >
                          > >
                          > > Anjal et al.,
                          > >
                          > >
                          > > It also shows up in Mark's photo, but not in the others. The physical
                          > effect is most likely due to the flow of this projectile in the whatever
                          > atmosphere it is encountering. Been a few years since I did fluid flow work
                          > related to projectiles, but the leading compressional wave and then a drop
                          > off is consistent with other photos that I have seen in bullet and airplane
                          > wind tunnel shots. So, it must be physically there. Also, one could deduce
                          > something about the properties of the atmosphere that it is encountering by
                          > measuring the spacing between light and dark areas and the comet body. But,
                          > I expect that real astrophysicists have already done that.
                          > >
                          > >
                          > > Note that it does not show up in the other photos, at least it is not as
                          > obvious. This is possible due to Photoshop processing. But these photos
                          > where the compression wave is not shown emphasize the actual solid body of
                          > the comet, so they are all part of a complete information package.
                          > >
                          > >
                          > > Thanks, for your comment. This is all very interesting.
                          > >
                          > >
                          > > Don
                          > >
                          > >
                          > >
                          > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                          > >
                          > >
                          > >
                          > >
                          > >
                          > >
                          > > Don,
                          > >
                          > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                          > > compression wave and pressure drop type effect too. I don't think it
                          > > is an artifact.
                          > >
                          > > Anjal.
                          > >
                          > > --- In brazosastro@ yahoogroups. com , "debclltx" <debray1@... > wrote:
                          > > >
                          > > > Gotta be careful to not creat effects that don't exist, but my recent
                          > > photo of Holmes when
                          > > > edited in Photoshop appears to show a leading compression wave and
                          > > then a pressure drop
                          > > > immediately behind it. This assumed that the comet is going to the
                          > > right. Any comments?
                          > > >
                          > > > Don
                          > > >
                          > >
                          > >
                          > >
                          > >
                          > >
                          > >
                          > > **** Note change in telephone numbers ****
                          > > Don E. Bray, Ph.D., P. E.
                          > > Don E. Bray, Inc.
                          > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                          > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                          > > USA
                          > > Office/Cellular 979-492-9534
                          > > Fax 979-693-1620
                          > > Res 979-693-1620
                          > > debray1@mac. com
                          > > debray1@brayengr. com
                          > > < http://brayengr. com>Astronomy photos
                          > http://homepage. mac.com/debray1/ PhotoAlbum22. html
                          > >
                          > >
                          >
                          >
                          >
                          >
                          > **** Note change in telephone numbers ****
                          > Don E. Bray, Ph.D., P. E.
                          > Don E. Bray, Inc.
                          > Mail P. O. Box 10315, College Station, Texas 77842-0315
                          > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                          > USA
                          > Office/Cellular 979-492-9534
                          > Fax 979-693-1620
                          > Res 979-693-1620
                          > debray1@mac. com
                          > debray1@brayengr. com
                          > <http://brayengr. com>Astronomy photos http://homepage. mac.com/debray1/
                          > PhotoAlbum22. html
                          >
                          >
                          >
                          > ____________ _________ _________ _________ _________ __
                          > Do You Yahoo!?
                          > Tired of spam? Yahoo! Mail has the best spam protection around
                          > http://mail. yahoo.com
                          >



                          __________________________________________________
                          Do You Yahoo!?
                          Tired of spam? Yahoo! Mail has the best spam protection around
                          http://mail.yahoo.com
                        • Kelsey Golden
                          Anjal, I just ordered a JMI NGF-DX2 low profile focuser from astromart for my Newtonian which should allow me to actually bring the DSI and/or webcams to
                          Message 12 of 19 , Nov 7, 2007
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                            Anjal,

                            I just ordered a JMI NGF-DX2 low profile focuser from astromart for my
                            Newtonian which should allow me to actually bring the DSI and/or
                            webcams to focus. It was supposedly shipped this morning from Ohio so
                            I would like to wait until I receive and install that focuser before
                            trying to image again. Right now, I am limited to guiding through my
                            80ED and taking photos through my unmodified Digital Rebel which can
                            reach focus in my Newtonian (barely). I think I might get better luck
                            out of my quickcam pro once I can actually bring it to focus.

                            Kelsey

                            On Nov 7, 2007 9:06 AM, <anjal_sharma@...> wrote:
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                            > Hi Kelsey,
                            >
                            > What version of Photoshop are you using? I have a really old version (PS
                            > 5.0LE) which doesn't have the ability to do discrete channels in the layers
                            > menu item. I use Meade's Image Processing subprogram in Autostar Suite to
                            > do the RGB conversion from the individual R G and B images saved as FITS
                            > files (won't work with JPEGs). Alternatively I have in the past done
                            > colorized images in my copy of PS, but you're right....it is a tedious
                            > process.
                            >
                            > Was your Luminosity filter screwed in to the nosepiece? For the best results
                            > the R, G and B filters should be in the filter slide bar while the L filter
                            > should be in the nosepiece to ensure that you cut off UV and IR light from
                            > entering the sensor for all images.
                            >
                            > BTW, I've been meaning to do narrowband imaging for some time now. I have a
                            > set of H-alpha, OIII, H-beta and SII filters for the job, but I've not made
                            > a serious effort thus far. How about we try narrowband imaging sometime
                            > this week? Let me know what your schedule is like.
                            >
                            > Anjal.
                            >
                            >
                            >
                            > ----- Original Message ----
                            > From: Kelsey Golden <kcgolden@...>
                            > To: brazosastro@yahoogroups.com
                            >
                            > Sent: Tuesday, November 6, 2007 10:32:15 PM
                            > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                            >
                            >
                            >
                            >
                            > I didn't adjust the weights at all. I copied each filtered black and
                            > white image (unedited) into the corresponding R, G, and B channel of
                            > the image which is something you can do in the "channels" tab of the
                            > layers window in photo shop. I then made an additional layer with
                            > properties set to "luminosity" which housed the luminosity filter
                            > image... at least I thought the L filter was in when I took it.
                            >
                            > I will try your method and see what happens although i believe that
                            > using the RGB channels tool in photoshop is a bit easier than
                            > colorizing each image before combining.
                            >
                            > Kelsey
                            >
                            > On Nov 6, 2007 3:20 PM, <anjal_sharma@ yahoo.com> wrote:
                            > >
                            > >
                            > >
                            > >
                            > >
                            > >
                            > >
                            > > Kelsey,
                            > >
                            > > Did you adjust the color weights on the R, G and B channels? You have to
                            > do
                            > > this to account for different spectral transmission areas by the filters
                            > at
                            > > the three primary colors and also for some spectral overlap between the B
                            > > and G filters and a gap in the spectrum between the G and R filters.
                            > Here's
                            > > an attachment which shows how the L R G abd B filters in your Meade
                            > filter
                            > > set behave. You can get a good guess as to color weight by using these
                            > > spectra.
                            > >
                            > > Also note the native spectra of the G and R filters. They let in
                            > > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                            > > filter. It lets in SIGNIFICANT amounts of UV light. Although not a
                            > problem
                            > > with your reflector, your ED80 and my Sky90 are apochromats and not
                            > > super-apochromats. They cannot focus the UV and IR light at the same
                            > point
                            > > as visible wavelengths.
                            > >
                            > > Therefore, unless you screw in the L filter which is the IR block filter
                            > in
                            > > the nosepiece of your DSI camera which is sensitive well into the UV and
                            > IR,
                            > > you're going to get slightly bloated stars in the LRGB image and perhaps
                            > a
                            > > bit of residual chroma as these UV and IR wavelengths will mix in with
                            > the
                            > > B, G and R wavelengths.
                            > >
                            > > Anjal.
                            > >
                            > >
                            > > ----- Original Message ----
                            > > From: Don E. Bray <debray1@mac. com>
                            > > To: brazosastro@ yahoogroups. com
                            > > Sent: Tuesday, November 6, 2007 2:59:18 PM
                            > > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                            > >
                            > >
                            > >
                            > >
                            > >
                            > > Kelsey,
                            > >
                            > > You are right, it is there. The difference in image density is subtle,
                            > but
                            > > if you look at it correctly, that outward leading front is unmistakably
                            > > there.
                            > >
                            > > Good work.
                            > >
                            > > Don
                            > >
                            > >
                            > > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                            > >
                            > >
                            > >
                            > >
                            > > Don and Anjal,
                            > >
                            > > I just put up my latest LRGB image of Holmes which was also taken on
                            > 11/02.
                            > > I'm kind of new to RGB processing and mine came out a much differen't
                            > color
                            > > than most of the images of Holmes that I've seen. Either the focus or the
                            > > exposure of the luminosity channel could've used some adjustment as well.
                            > At
                            > > any rate, you can see the same issues as you describe in my photo as
                            > well.
                            > >
                            > > Kelsey
                            > >
                            > > On 11/6/07, Don E. Bray <debray1@mac. com> wrote:
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > > Anjal et al.,
                            > > >
                            > > >
                            > > > It also shows up in Mark's photo, but not in the others. The physical
                            > > effect is most likely due to the flow of this projectile in the whatever
                            > > atmosphere it is encountering. Been a few years since I did fluid flow
                            > work
                            > > related to projectiles, but the leading compressional wave and then a
                            > drop
                            > > off is consistent with other photos that I have seen in bullet and
                            > airplane
                            > > wind tunnel shots. So, it must be physically there. Also, one could
                            > deduce
                            > > something about the properties of the atmosphere that it is encountering
                            > by
                            > > measuring the spacing between light and dark areas and the comet body.
                            > But,
                            > > I expect that real astrophysicists have already done that.
                            > > >
                            > > >
                            > > > Note that it does not show up in the other photos, at least it is not
                            > as
                            > > obvious. This is possible due to Photoshop processing. But these photos
                            > > where the compression wave is not shown emphasize the actual solid body
                            > of
                            > > the comet, so they are all part of a complete information package.
                            > > >
                            > > >
                            > > > Thanks, for your comment. This is all very interesting.
                            > > >
                            > > >
                            > > > Don
                            > > >
                            > > >
                            > > >
                            > > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > > Don,
                            > > >
                            > > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                            > > > compression wave and pressure drop type effect too. I don't think it
                            > > > is an artifact.
                            > > >
                            > > > Anjal.
                            > > >
                            > > > --- In brazosastro@ yahoogroups. com , "debclltx" <debray1@... > wrote:
                            > > > >
                            > > > > Gotta be careful to not creat effects that don't exist, but my recent
                            > > > photo of Holmes when
                            > > > > edited in Photoshop appears to show a leading compression wave and
                            > > > then a pressure drop
                            > > > > immediately behind it. This assumed that the comet is going to the
                            > > > right. Any comments?
                            > > > >
                            > > > > Don
                            > > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > > **** Note change in telephone numbers ****
                            > > > Don E. Bray, Ph.D., P. E.
                            > > > Don E. Bray, Inc.
                            > > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                            > > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                            > > > USA
                            > > > Office/Cellular 979-492-9534
                            > > > Fax 979-693-1620
                            > > > Res 979-693-1620
                            > > > debray1@mac. com
                            > > > debray1@brayengr. com
                            > > > < http://brayengr. com>Astronomy photos
                            > > http://homepage. mac.com/debray1/ PhotoAlbum22. html
                            > > >
                            > > >
                            > >
                            > >
                            > >
                            > >
                            > > **** Note change in telephone numbers ****
                            > > Don E. Bray, Ph.D., P. E.
                            > > Don E. Bray, Inc.
                            > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                            > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                            > > USA
                            > > Office/Cellular 979-492-9534
                            > > Fax 979-693-1620
                            > > Res 979-693-1620
                            > > debray1@mac. com
                            > > debray1@brayengr. com
                            > > <http://brayengr. com>Astronomy photos http://homepage. mac.com/debray1/
                            > > PhotoAlbum22. html
                            > >
                            > >
                            > >
                            > > ____________ _________ _________ _________ _________ __
                            > > Do You Yahoo!?
                            > > Tired of spam? Yahoo! Mail has the best spam protection around
                            > > http://mail. yahoo.com
                            > >
                            >
                            >
                            >
                            > __________________________________________________
                            > Do You Yahoo!?
                            > Tired of spam? Yahoo! Mail has the best spam protection around
                            > http://mail.yahoo.com
                            >
                            >
                          • Michael Prokosch
                            All this talk about the compression wave...I forgot to say that I observed it last weekend with Sam Houston s 24 Dob. The compression wave you talk about was
                            Message 13 of 19 , Nov 7, 2007
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                              All this talk about the compression wave...I forgot to say that I observed it last weekend with Sam Houston's 24" Dob.  The compression wave you talk about was visible in the eyepiece, rather easily...I hope to get another crack at it tonight...our last labs at the observatory for the semester are this week, so soon I'll have the observatory almost entirely to myself again. 

                              anjal_sharma@... wrote:
                              Kelsey,

                              Did you adjust the color weights on the R, G and B channels?  You have to do this to account for different spectral transmission areas by the filters at the three primary colors and also for some spectral overlap between the B and G filters and a gap in the spectrum between the G and R filters.  Here's an attachment which shows how the L R G abd B filters in your Meade filter set behave.  You can get a good guess as to color weight by using these spectra. 

                              Also note the native spectra of the G and R filters.  They let in SIGNIFICANT amounts of IR light.  Note also the native spectrum of the B filter.  It lets in SIGNIFICANT amounts of UV light.  Although not a problem with your reflector, your ED80 and my Sky90 are apochromats and not super-apochromats.  They cannot focus the UV and IR light at the same point as visible wavelengths.

                              Therefore, unless you screw in the L filter which is the IR block filter in the nosepiece of your DSI camera which is sensitive well into the UV and IR, you're going to get slightly bloated stars in the LRGB image and perhaps a bit of residual chroma as these UV and IR wavelengths will mix in with the B, G and R wavelengths. 

                              Anjal.

                              ----- Original Message ----
                              From: Don E. Bray <debray1@mac. com>
                              To: brazosastro@ yahoogroups. com
                              Sent: Tuesday, November 6, 2007 2:59:18 PM
                              Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave

                              Kelsey,

                              You are right, it is there. The difference in image density is subtle, but if you look at it correctly, that outward leading front is unmistakably there.

                              Good work.

                              Don

                              On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:

                              Don and Anjal,

                              I just put up my latest LRGB image of Holmes which was also taken on 11/02. I'm kind of new to RGB processing and mine came out a much differen't color than most of the images of Holmes that I've seen. Either the focus or the exposure of the luminosity channel could've used some adjustment as well. At any rate, you can see the same issues as you describe in my photo as well.

                              Kelsey

                              On 11/6/07, Don E. Bray <debray1@mac.com> wrote:
                              Anjal et al.,

                              It also shows up in Mark's photo, but not in the others. The physical effect is most likely due to the flow of this projectile in the whatever atmosphere it is encountering. Been a few years since I did fluid flow work related to projectiles, but the leading compressional wave and then a drop off is consistent with other photos that I have seen in bullet and airplane wind tunnel shots. So, it must be physically there. Also, one could deduce something about the properties of the atmosphere that it is encountering by measuring the spacing between light and dark areas and the comet body. But, I expect that real astrophysicists have already done that.

                              Note that it does not show up in the other photos, at least it is not as obvious. This is possible due to Photoshop processing. But these photos where the compression wave is not shown emphasize the actual solid body of the comet, so they are all part of a complete information package.

                              Thanks, for your comment. This is all very interesting.

                              Don

                              On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:

                              Don,

                              My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                              compression wave and pressure drop type effect too. I don't think it
                              is an artifact.

                              Anjal.

                              --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                              >
                              > Gotta be careful to not creat effects that don't exist, but my recent
                              photo of Holmes when
                              > edited in Photoshop appears to show a leading compression wave and
                              then a pressure drop
                              > immediately behind it. This assumed that the comet is going to the
                              right. Any comments?
                              >
                              > Don
                              >



                              **** Note change in telephone numbers ****
                              Don E. Bray, Ph.D., P. E.
                              Don E. Bray, Inc.
                              Mail P. O. Box 10315, College Station, Texas 77842-0315
                              Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                              USA
                              Office/Cellular 979-492-9534
                              Fax 979-693-1620
                              Res 979-693-1620
                              Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html




                              **** Note change in telephone numbers ****
                              Don E. Bray, Ph.D., P. E.
                              Don E. Bray, Inc.
                              Mail P. O. Box 10315, College Station, Texas 77842-0315
                              Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                              USA
                              Office/Cellular 979-492-9534
                              Fax 979-693-1620
                              Res 979-693-1620
                              Astronomy photos http://homepage. mac.com/debray1/ PhotoAlbum22. html



                              ____________ _________ _________ _________ _________ __
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                            • Kelsey Golden
                              Michael, What a great job you have! About the compression wave, have we ruled out the possibility that it s just an optical illusion created by the angle at
                              Message 14 of 19 , Nov 7, 2007
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                                Michael,

                                What a great job you have!

                                About the compression wave, have we ruled out the possibility that
                                it's just an optical illusion created by the angle at which we are
                                viewing the comet? Forgive me for being ignorant but are comets
                                supposed to have a compression wave?

                                Kelsey

                                On Nov 7, 2007 3:37 PM, Michael Prokosch <star2_watch@...> wrote:
                                >
                                >
                                >
                                >
                                >
                                >
                                > All this talk about the compression wave...I forgot to say that I observed
                                > it last weekend with Sam Houston's 24" Dob. The compression wave you talk
                                > about was visible in the eyepiece, rather easily...I hope to get another
                                > crack at it tonight...our last labs at the observatory for the semester are
                                > this week, so soon I'll have the observatory almost entirely to myself
                                > again.
                                >
                                >
                                > anjal_sharma@... wrote:
                                >
                                >
                                >
                                >
                                >
                                > Kelsey,
                                >
                                > Did you adjust the color weights on the R, G and B channels? You have to do
                                > this to account for different spectral transmission areas by the filters at
                                > the three primary colors and also for some spectral overlap between the B
                                > and G filters and a gap in the spectrum between the G and R filters. Here's
                                > an attachment which shows how the L R G abd B filters in your Meade filter
                                > set behave. You can get a good guess as to color weight by using these
                                > spectra.
                                >
                                > Also note the native spectra of the G and R filters. They let in
                                > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                                > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                                > with your reflector, your ED80 and my Sky90 are apochromats and not
                                > super-apochromats. They cannot focus the UV and IR light at the same point
                                > as visible wavelengths.
                                >
                                > Therefore, unless you screw in the L filter which is the IR block filter in
                                > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                                > you're going to get slightly bloated stars in the LRGB image and perhaps a
                                > bit of residual chroma as these UV and IR wavelengths will mix in with the
                                > B, G and R wavelengths.
                                >
                                > Anjal.
                                >
                                >
                                > ----- Original Message ----
                                > From: Don E. Bray <debray1@...>
                                > To: brazosastro@yahoogroups.com
                                > Sent: Tuesday, November 6, 2007 2:59:18 PM
                                > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                                >
                                >
                                >
                                > Kelsey,
                                >
                                >
                                > You are right, it is there. The difference in image density is subtle, but
                                > if you look at it correctly, that outward leading front is unmistakably
                                > there.
                                >
                                >
                                > Good work.
                                >
                                >
                                > Don
                                >
                                >
                                >
                                > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                                >
                                >
                                >
                                >
                                >
                                > Don and Anjal,
                                >
                                > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                                > I'm kind of new to RGB processing and mine came out a much differen't color
                                > than most of the images of Holmes that I've seen. Either the focus or the
                                > exposure of the luminosity channel could've used some adjustment as well. At
                                > any rate, you can see the same issues as you describe in my photo as well.
                                >
                                > Kelsey
                                >
                                >
                                > On 11/6/07, Don E. Bray <debray1@...> wrote:
                                > >
                                > >
                                > >
                                > >
                                > >
                                > > Anjal et al.,
                                > >
                                > >
                                > > It also shows up in Mark's photo, but not in the others. The physical
                                > effect is most likely due to the flow of this projectile in the whatever
                                > atmosphere it is encountering. Been a few years since I did fluid flow work
                                > related to projectiles, but the leading compressional wave and then a drop
                                > off is consistent with other photos that I have seen in bullet and airplane
                                > wind tunnel shots. So, it must be physically there. Also, one could deduce
                                > something about the properties of the atmosphere that it is encountering by
                                > measuring the spacing between light and dark areas and the comet body. But,
                                > I expect that real astrophysicists have already done that.
                                > >
                                > >
                                > > Note that it does not show up in the other photos, at least it is not as
                                > obvious. This is possible due to Photoshop processing. But these photos
                                > where the compression wave is not shown emphasize the actual solid body of
                                > the comet, so they are all part of a complete information package.
                                > >
                                > >
                                > > Thanks, for your comment. This is all very interesting.
                                > >
                                > >
                                > > Don
                                > >
                                > >
                                > >
                                > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                                > >
                                > >
                                > >
                                > >
                                > >
                                > > Don,
                                > >
                                > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                                > > compression wave and pressure drop type effect too. I don't think it
                                > > is an artifact.
                                > >
                                > > Anjal.
                                > >
                                > > --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                                > > >
                                > > > Gotta be careful to not creat effects that don't exist, but my recent
                                > > photo of Holmes when
                                > > > edited in Photoshop appears to show a leading compression wave and
                                > > then a pressure drop
                                > > > immediately behind it. This assumed that the comet is going to the
                                > > right. Any comments?
                                > > >
                                > > > Don
                                > > >
                                > >
                                > >
                                > >
                                > >
                                > >
                                > >
                                > > **** Note change in telephone numbers ****
                                > > Don E. Bray, Ph.D., P. E.
                                > > Don E. Bray, Inc.
                                > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                > > USA
                                > > Office/Cellular 979-492-9534
                                > > Fax 979-693-1620
                                > > Res 979-693-1620
                                > > debray1@...
                                > > debray1@...
                                > > < http://brayengr.com>Astronomy photos
                                > http://homepage.mac.com/debray1/PhotoAlbum22.html
                                > >
                                > >
                                >
                                >
                                >
                                >
                                >
                                >
                                > **** Note change in telephone numbers ****
                                > Don E. Bray, Ph.D., P. E.
                                > Don E. Bray, Inc.
                                > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                > USA
                                > Office/Cellular 979-492-9534
                                > Fax 979-693-1620
                                > Res 979-693-1620
                                > debray1@mac. com
                                > debray1@brayengr. com
                                > <http://brayengr. com>Astronomy photos http://homepage. mac.com/debray1/
                                > PhotoAlbum22. html
                                >
                                >
                                >
                                > __________________________________________________
                                > Do You Yahoo!?
                                > Tired of spam? Yahoo! Mail has the best spam protection around
                                > http://mail.yahoo.com
                                >
                                >
                                >
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                                > http://mail.yahoo.com
                                >
                                >
                              • Don E. Bray
                                The subtle changes that we see at the leading edge are caused by differences in the density and the associated light speed of the material, hence there are
                                Message 15 of 19 , Nov 7, 2007
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                                  The subtle changes that we see at the leading edge are caused by differences in the density and the associated  light speed of the material, hence there are differences in the diffraction of the light coming from the comet.  This effect continues right up to the edge of the "rock" as well as the trailing tail.

                                  Don



                                  On 7 Nov 2007, at 4:29 PM, Kelsey Golden wrote:

                                  Michael,

                                  What a great job you have!

                                  About the compression wave, have we ruled out the possibility that
                                  it's just an optical illusion created by the angle at which we are
                                  viewing the comet? Forgive me for being ignorant but are comets
                                  supposed to have a compression wave?

                                  Kelsey

                                  On Nov 7, 2007 3:37 PM, Michael Prokosch <star2_watch@yahoo.com> wrote:
                                  >
                                  >
                                  >
                                  >
                                  >
                                  >
                                  > All this talk about the compression wave...I forgot to say that I observed
                                  > it last weekend with Sam Houston's 24" Dob. The compression wave you talk
                                  > about was visible in the eyepiece, rather easily...I hope to get another
                                  > crack at it tonight...our last labs at the observatory for the semester are
                                  > this week, so soon I'll have the observatory almost entirely to myself
                                  > again.
                                  >
                                  >
                                  > anjal_sharma@yahoo.com wrote:
                                  >
                                  >
                                  >
                                  >
                                  >
                                  > Kelsey,
                                  >
                                  > Did you adjust the color weights on the R, G and B channels? You have to do
                                  > this to account for different spectral transmission areas by the filters at
                                  > the three primary colors and also for some spectral overlap between the B
                                  > and G filters and a gap in the spectrum between the G and R filters. Here's
                                  > an attachment which shows how the L R G abd B filters in your Meade filter
                                  > set behave. You can get a good guess as to color weight by using these
                                  > spectra.
                                  >
                                  > Also note the native spectra of the G and R filters. They let in
                                  > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                                  > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                                  > with your reflector, your ED80 and my Sky90 are apochromats and not
                                  > super-apochromats. They cannot focus the UV and IR light at the same point
                                  > as visible wavelengths.
                                  >
                                  > Therefore, unless you screw in the L filter which is the IR block filter in
                                  > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                                  > you're going to get slightly bloated stars in the LRGB image and perhaps a
                                  > bit of residual chroma as these UV and IR wavelengths will mix in with the
                                  > B, G and R wavelengths.
                                  >
                                  > Anjal.
                                  >
                                  >
                                  > ----- Original Message ----
                                  > From: Don E. Bray <debray1@mac.com>
                                  > To: brazosastro@yahoogroups.com
                                  > Sent: Tuesday, November 6, 2007 2:59:18 PM
                                  > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                                  >
                                  >
                                  >
                                  > Kelsey,
                                  >
                                  >
                                  > You are right, it is there. The difference in image density is subtle, but
                                  > if you look at it correctly, that outward leading front is unmistakably
                                  > there.
                                  >
                                  >
                                  > Good work.
                                  >
                                  >
                                  > Don
                                  >
                                  >
                                  >
                                  > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                                  >
                                  >
                                  >
                                  >
                                  >
                                  > Don and Anjal,
                                  >
                                  > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                                  > I'm kind of new to RGB processing and mine came out a much differen't color
                                  > than most of the images of Holmes that I've seen. Either the focus or the
                                  > exposure of the luminosity channel could've used some adjustment as well. At
                                  > any rate, you can see the same issues as you describe in my photo as well.
                                  >
                                  > Kelsey
                                  >
                                  >
                                  > On 11/6/07, Don E. Bray <debray1@mac.com> wrote:
                                  > >
                                  > >
                                  > >
                                  > >
                                  > >
                                  > > Anjal et al.,
                                  > >
                                  > >
                                  > > It also shows up in Mark's photo, but not in the others. The physical
                                  > effect is most likely due to the flow of this projectile in the whatever
                                  > atmosphere it is encountering. Been a few years since I did fluid flow work
                                  > related to projectiles, but the leading compressional wave and then a drop
                                  > off is consistent with other photos that I have seen in bullet and airplane
                                  > wind tunnel shots. So, it must be physically there. Also, one could deduce
                                  > something about the properties of the atmosphere that it is encountering by
                                  > measuring the spacing between light and dark areas and the comet body. But,
                                  > I expect that real astrophysicists have already done that.
                                  > >
                                  > >
                                  > > Note that it does not show up in the other photos, at least it is not as
                                  > obvious. This is possible due to Photoshop processing. But these photos
                                  > where the compression wave is not shown emphasize the actual solid body of
                                  > the comet, so they are all part of a complete information package.
                                  > >
                                  > >
                                  > > Thanks, for your comment. This is all very interesting.
                                  > >
                                  > >
                                  > > Don
                                  > >
                                  > >
                                  > >
                                  > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                                  > >
                                  > >
                                  > >
                                  > >
                                  > >
                                  > > Don,
                                  > >
                                  > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                                  > > compression wave and pressure drop type effect too. I don't think it
                                  > > is an artifact.
                                  > >
                                  > > Anjal.
                                  > >
                                  > > --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                                  > > >
                                  > > > Gotta be careful to not creat effects that don't exist, but my recent
                                  > > photo of Holmes when
                                  > > > edited in Photoshop appears to show a leading compression wave and
                                  > > then a pressure drop
                                  > > > immediately behind it. This assumed that the comet is going to the
                                  > > right. Any comments?
                                  > > >
                                  > > > Don
                                  > > >
                                  > >
                                  > >
                                  > >
                                  > >
                                  > >
                                  > >
                                  > > **** Note change in telephone numbers ****
                                  > > Don E. Bray, Ph.D., P. E.
                                  > > Don E. Bray, Inc.
                                  > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                  > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                  > > USA
                                  > > Office/Cellular 979-492-9534
                                  > > Fax 979-693-1620
                                  > > Res 979-693-1620
                                  > > debray1@mac.com
                                  > > debray1@brayengr.com
                                  > > < http://brayengr.com>Astronomy photos
                                  > http://homepage.mac.com/debray1/PhotoAlbum22.html
                                  > >
                                  > >
                                  >
                                  >
                                  >
                                  >
                                  >
                                  >
                                  > **** Note change in telephone numbers ****
                                  > Don E. Bray, Ph.D., P. E.
                                  > Don E. Bray, Inc.
                                  > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                  > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                  > USA
                                  > Office/Cellular 979-492-9534
                                  > Fax 979-693-1620
                                  > Res 979-693-1620
                                  > debray1@mac. com
                                  > debray1@brayengr. com
                                  > <http://brayengr. com>Astronomy photos http://homepage. mac.com/debray1/
                                  > PhotoAlbum22. html
                                  >
                                  >
                                  >
                                  > __________________________________________________
                                  > Do You Yahoo!?
                                  > Tired of spam? Yahoo! Mail has the best spam protection around
                                  > http://mail.yahoo.com
                                  >
                                  >
                                  >
                                  > __________________________________________________
                                  > Do You Yahoo!?
                                  > Tired of spam? Yahoo! Mail has the best spam protection around
                                  > http://mail.yahoo.com
                                  >
                                  >


                                  **** Note change in telephone numbers ****
                                  Don E. Bray, Ph.D., P. E.
                                  Don E. Bray, Inc.
                                  Mail P. O. Box 10315, College Station, Texas 77842-0315
                                  Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                  USA
                                  Office/Cellular 979-492-9534
                                  Fax 979-693-1620
                                  Res 979-693-1620
                                  Astronomy photos http://homepage.mac.com/debray1/PhotoAlbum22.html

                                • Don E. Bray
                                  Maybe I need to add a little more. The compression wave is at the very front of the disturbance, leading the comet rock by some distance. This area is
                                  Message 16 of 19 , Nov 7, 2007
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                                    Maybe I need to add a little more. The compression wave is at the very front of the disturbance, leading the comet "rock" by some distance. This area is slightly lighter than the rest. Then, as you travel back toward the rock the appearance becomes slightly darker, indicating a change in pressure and density. There are variations as you go toward the comet itself until you see a very thin layer at the very front of the comet. This is all traveling at the speed of the comet. 

                                    Don
                                     
                                    On 7 Nov 2007, at 4:39 PM, Don E. Bray wrote:

                                    The subtle changes that we see at the leading edge are caused by differences in the density and the associated  light speed of the material, hence there are differences in the diffraction of the light coming from the comet.  This effect continues right up to the edge of the "rock" as well as the trailing tail.


                                    Don



                                    On 7 Nov 2007, at 4:29 PM, Kelsey Golden wrote:

                                    Michael,

                                    What a great job you have!

                                    About the compression wave, have we ruled out the possibility that
                                    it's just an optical illusion created by the angle at which we are
                                    viewing the comet? Forgive me for being ignorant but are comets
                                    supposed to have a compression wave?

                                    Kelsey

                                    On Nov 7, 2007 3:37 PM, Michael Prokosch <star2_watch@yahoo.com> wrote:
                                    >
                                    >
                                    >
                                    >
                                    >
                                    >
                                    > All this talk about the compression wave...I forgot to say that I observed
                                    > it last weekend with Sam Houston's 24" Dob. The compression wave you talk
                                    > about was visible in the eyepiece, rather easily...I hope to get another
                                    > crack at it tonight...our last labs at the observatory for the semester are
                                    > this week, so soon I'll have the observatory almost entirely to myself
                                    > again.
                                    >
                                    >
                                    > anjal_sharma@yahoo.com wrote:
                                    >
                                    >
                                    >
                                    >
                                    >
                                    > Kelsey,
                                    >
                                    > Did you adjust the color weights on the R, G and B channels? You have to do
                                    > this to account for different spectral transmission areas by the filters at
                                    > the three primary colors and also for some spectral overlap between the B
                                    > and G filters and a gap in the spectrum between the G and R filters. Here's
                                    > an attachment which shows how the L R G abd B filters in your Meade filter
                                    > set behave. You can get a good guess as to color weight by using these
                                    > spectra.
                                    >
                                    > Also note the native spectra of the G and R filters. They let in
                                    > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                                    > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                                    > with your reflector, your ED80 and my Sky90 are apochromats and not
                                    > super-apochromats. They cannot focus the UV and IR light at the same point
                                    > as visible wavelengths.
                                    >
                                    > Therefore, unless you screw in the L filter which is the IR block filter in
                                    > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                                    > you're going to get slightly bloated stars in the LRGB image and perhaps a
                                    > bit of residual chroma as these UV and IR wavelengths will mix in with the
                                    > B, G and R wavelengths.
                                    >
                                    > Anjal.
                                    >
                                    >
                                    > ----- Original Message ----
                                    > From: Don E. Bray <debray1@mac.com>
                                    > To: brazosastro@yahoogroups.com
                                    > Sent: Tuesday, November 6, 2007 2:59:18 PM
                                    > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                                    >
                                    >
                                    >
                                    > Kelsey,
                                    >
                                    >
                                    > You are right, it is there. The difference in image density is subtle, but
                                    > if you look at it correctly, that outward leading front is unmistakably
                                    > there.
                                    >
                                    >
                                    > Good work.
                                    >
                                    >
                                    > Don
                                    >
                                    >
                                    >
                                    > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                                    >
                                    >
                                    >
                                    >
                                    >
                                    > Don and Anjal,
                                    >
                                    > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                                    > I'm kind of new to RGB processing and mine came out a much differen't color
                                    > than most of the images of Holmes that I've seen. Either the focus or the
                                    > exposure of the luminosity channel could've used some adjustment as well. At
                                    > any rate, you can see the same issues as you describe in my photo as well.
                                    >
                                    > Kelsey
                                    >
                                    >
                                    > On 11/6/07, Don E. Bray <debray1@mac.com> wrote:
                                    > >
                                    > >
                                    > >
                                    > >
                                    > >
                                    > > Anjal et al.,
                                    > >
                                    > >
                                    > > It also shows up in Mark's photo, but not in the others. The physical
                                    > effect is most likely due to the flow of this projectile in the whatever
                                    > atmosphere it is encountering. Been a few years since I did fluid flow work
                                    > related to projectiles, but the leading compressional wave and then a drop
                                    > off is consistent with other photos that I have seen in bullet and airplane
                                    > wind tunnel shots. So, it must be physically there. Also, one could deduce
                                    > something about the properties of the atmosphere that it is encountering by
                                    > measuring the spacing between light and dark areas and the comet body. But,
                                    > I expect that real astrophysicists have already done that.
                                    > >
                                    > >
                                    > > Note that it does not show up in the other photos, at least it is not as
                                    > obvious. This is possible due to Photoshop processing. But these photos
                                    > where the compression wave is not shown emphasize the actual solid body of
                                    > the comet, so they are all part of a complete information package.
                                    > >
                                    > >
                                    > > Thanks, for your comment. This is all very interesting.
                                    > >
                                    > >
                                    > > Don
                                    > >
                                    > >
                                    > >
                                    > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                                    > >
                                    > >
                                    > >
                                    > >
                                    > >
                                    > > Don,
                                    > >
                                    > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                                    > > compression wave and pressure drop type effect too. I don't think it
                                    > > is an artifact.
                                    > >
                                    > > Anjal.
                                    > >
                                    > > --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                                    > > >
                                    > > > Gotta be careful to not creat effects that don't exist, but my recent
                                    > > photo of Holmes when
                                    > > > edited in Photoshop appears to show a leading compression wave and
                                    > > then a pressure drop
                                    > > > immediately behind it. This assumed that the comet is going to the
                                    > > right. Any comments?
                                    > > >
                                    > > > Don
                                    > > >
                                    > >
                                    > >
                                    > >
                                    > >
                                    > >
                                    > >
                                    > > **** Note change in telephone numbers ****
                                    > > Don E. Bray, Ph.D., P. E.
                                    > > Don E. Bray, Inc.
                                    > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                    > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                    > > USA
                                    > > Office/Cellular 979-492-9534
                                    > > Fax 979-693-1620
                                    > > Res 979-693-1620
                                    > > debray1@mac.com
                                    > > debray1@brayengr.com
                                    > > < http://brayengr.

                                  • Karl Williams
                                    Forgive my ignorance here, but is this compression wave that same phemonon that is being reported as debris from an explosion on the comet (NASA & CNN) that
                                    Message 17 of 19 , Nov 8, 2007
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                                      Forgive my ignorance here, but is this compression wave that same phemonon that is being reported as debris from an explosion on the comet (NASA & CNN) that suddenly made the comet visible to the naked eye?
                                       
                                      Karl

                                      "Don E. Bray" <debray1@...> wrote:
                                      Maybe I need to add a little more. The compression wave is at the very front of the disturbance, leading the comet "rock" by some distance. This area is slightly lighter than the rest. Then, as you travel back toward the rock the appearance becomes slightly darker, indicating a change in pressure and density. There are variations as you go toward the comet itself until you see a very thin layer at the very front of the comet. This is all traveling at the speed of the comet. 

                                      Don

                                      On 7 Nov 2007, at 4:39 PM, Don E. Bray wrote:

                                      The subtle changes that we see at the leading edge are caused by differences in the density and the associated  light speed of the material, hence there are differences in the diffraction of the light coming from the comet.  This effect continues right up to the edge of the "rock" as well as the trailing tail.

                                      Don



                                      On 7 Nov 2007, at 4:29 PM, Kelsey Golden wrote:

                                      Michael,

                                      What a great job you have!

                                      About the compression wave, have we ruled out the possibility that
                                      it's just an optical illusion created by the angle at which we are
                                      viewing the comet? Forgive me for being ignorant but are comets
                                      supposed to have a compression wave?

                                      Kelsey

                                      On Nov 7, 2007 3:37 PM, Michael Prokosch <star2_watch@yahoo.com> wrote:
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      > All this talk about the compression wave...I forgot to say that I observed
                                      > it last weekend with Sam Houston's 24" Dob. The compression wave you talk
                                      > about was visible in the eyepiece, rather easily...I hope to get another
                                      > crack at it tonight...our last labs at the observatory for the semester are
                                      > this week, so soon I'll have the observatory almost entirely to myself
                                      > again.
                                      >
                                      >
                                      > anjal_sharma@yahoo.com wrote:
                                      >
                                      >
                                      >
                                      >
                                      >
                                      > Kelsey,
                                      >
                                      > Did you adjust the color weights on the R, G and B channels? You have to do
                                      > this to account for different spectral transmission areas by the filters at
                                      > the three primary colors and also for some spectral overlap between the B
                                      > and G filters and a gap in the spectrum between the G and R filters. Here's
                                      > an attachment which shows how the L R G abd B filters in your Meade filter
                                      > set behave. You can get a good guess as to color weight by using these
                                      > spectra.
                                      >
                                      > Also note the native spectra of the G and R filters. They let in
                                      > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                                      > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                                      > with your reflector, your ED80 and my Sky90 are apochromats and not
                                      > super-apochromats. They cannot focus the UV and IR light at the same point
                                      > as visible wavelengths.
                                      >
                                      > Therefore, unless you screw in the L filter which is the IR block filter in
                                      > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                                      > you're going to get slightly bloated stars in the LRGB image and perhaps a
                                      > bit of residual chroma as these UV and IR wavelengths will mix in with the
                                      > B, G and R wavelengths.
                                      >
                                      > Anjal.
                                      >
                                      >
                                      > ----- Original Message ----
                                      > From: Don E. Bray <debray1@mac.com>
                                      > To: brazosastro@yahoogroups.com
                                      > Sent: Tuesday, November 6, 2007 2:59:18 PM
                                      > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                                      >
                                      >
                                      >
                                      > Kelsey,
                                      >
                                      >
                                      > You are right, it is there. The difference in image density is subtle, but
                                      > if you look at it correctly, that outward leading front is unmistakably
                                      > there.
                                      >
                                      >
                                      > Good work.
                                      >
                                      >
                                      > Don
                                      >
                                      >
                                      >
                                      > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                                      >
                                      >
                                      >
                                      >
                                      >
                                      > Don and Anjal,
                                      >
                                      > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                                      > I'm kind of new to RGB processing and mine came out a much differen't color
                                      > than most of the images of Holmes that I've seen. Either the focus or the
                                      > exposure of the luminosity channel could've used some adjustment as well. At
                                      > any rate, you can see the same issues as you describe in my photo as well.
                                      >
                                      > Kelsey
                                      >
                                      >
                                      > On 11/6/07, Don E. Bray <debray1@mac.com> wrote:
                                      > >
                                      > >
                                      > >
                                      > >
                                      > >
                                      > > Anjal et al.,
                                      > >
                                      > >
                                      > > It also shows up in Mark's photo, but not in the others. The physical
                                      > effect is most likely due to the flow of this projectile in the whatever
                                      > atmosphere it is encountering. Been a few years since I did fluid flow work
                                      > related to projectiles, but the leading compressional wave and then a drop
                                      > off is consistent with other photos that I have seen in bullet and airplane
                                      > wind tunnel shots. So, it must be physically there. Also, one could deduce
                                      > something about the properties of the atmosphere that it is encountering by
                                      > measuring the spacing between light and dark areas and the comet body. But,
                                      > I expect that real astrophysicists have already done that.
                                      > >
                                      > >
                                      > > Note that it does not show up in the other photos, at least it is not as
                                      > obvious. This is possible due to Photoshop processing. But these photos
                                      > where the compression wave is not shown emphasize the actual solid body of
                                      > the comet, so they are all part of a complete information package.
                                      > >
                                      > >
                                      > > Thanks, for your comment. This is all very interesting.
                                      > >
                                      > >
                                      > > Don
                                      > >
                                      > >
                                      > >
                                      > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                                      > >
                                      > >
                                      > >
                                      > >
                                      > >
                                      > > Don,
                                      > >
                                      > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                                      > > compression wave and pressure drop type effect too. I don't think it
                                      > > is an artifact.
                                      > >
                                      > > Anjal.
                                      > >
                                      > > --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                                      > > >
                                      > > > Gotta be careful to not creat effects that don't exist, but my recent
                                      > > photo of Holmes when
                                      > > > edited in Photoshop appears to show a leading compression wave and
                                      > > then a pressure drop
                                      > > > immediately behind it. This assumed that the comet is going to the
                                      > > right. Any comments?
                                      > > >
                                      > > > Don
                                      > > >
                                      > >
                                      > >
                                      > >
                                      > >
                                      > >
                                      > >
                                      > > **** Note change in telephone numbers ****
                                      > > Don E. Bray, Ph.D., P. E.
                                      > > Don E. Bray, Inc.
                                      > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                      > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                      > > USA
                                      > > Office/Cellular 979-492-9534
                                      > > Fax 979-693-1620
                                      > > Res 979-693-1620
                                      > > debray1@mac.com
                                      > > debray1@brayengr.com
                                      > > < http://brayengr.com>Astronomy photos
                                      > http://homepage.mac.com/debray1/PhotoAlbum22.html
                                      > >
                                      > >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      > **** Note change in telephone numbers ****
                                      > Don E. Bray, Ph.D., P. E.
                                      > Don E. Bray, Inc.
                                      > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                      > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                      > USA
                                      > Office/Cellular 979-492-9534
                                      > Fax 979-693-1620
                                      > Res 979-693-1620
                                      > debray1@mac. com
                                      > debray1@brayengr. com
                                      > <http://brayengr. com>Astronomy photos http://homepage. mac.com/debray1/
                                      > PhotoAlbum22. html
                                      >
                                      >
                                      >
                                      > __________________________________________________
                                      > Do You Yahoo!?
                                      > Tired of spam? Yahoo! Mail has the best spam protection around
                                      > http://mail.yahoo.com
                                      >
                                      >
                                      >
                                      > __________________________________________________
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                                      > http://mail.yahoo.com
                                      >
                                      >

                                    • Michael Prokosch
                                      yes, that is what is most likely is. Some of it is outgassing that has taken place after the explosion, but at least a portion of it is from the explosion
                                      Message 18 of 19 , Nov 8, 2007
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                                        yes, that is what is most likely is.  Some of it is outgassing that has taken place after the explosion, but at least a portion of it is from the explosion itself. 

                                        Karl Williams <engineer_kc5ixx@...> wrote:
                                        Forgive my ignorance here, but is this compression wave that same phemonon that is being reported as debris from an explosion on the comet (NASA & CNN) that suddenly made the comet visible to the naked eye?
                                         
                                        Karl

                                        "Don E. Bray" <debray1@mac. com> wrote:
                                        Maybe I need to add a little more. The compression wave is at the very front of the disturbance, leading the comet "rock" by some distance. This area is slightly lighter than the rest. Then, as you travel back toward the rock the appearance becomes slightly darker, indicating a change in pressure and density. There are variations as you go toward the comet itself until you see a very thin layer at the very front of the comet. This is all traveling at the speed of the comet. 

                                        Don

                                        On 7 Nov 2007, at 4:39 PM, Don E. Bray wrote:

                                        The subtle changes that we see at the leading edge are caused by differences in the density and the associated  light speed of the material, hence there are differences in the diffraction of the light coming from the comet.  This effect continues right up to the edge of the "rock" as well as the trailing tail.

                                        Don



                                        On 7 Nov 2007, at 4:29 PM, Kelsey Golden wrote:

                                        Michael,

                                        What a great job you have!

                                        About the compression wave, have we ruled out the possibility that
                                        it's just an optical illusion created by the angle at which we are
                                        viewing the comet? Forgive me for being ignorant but are comets
                                        supposed to have a compression wave?

                                        Kelsey

                                        On Nov 7, 2007 3:37 PM, Michael Prokosch <star2_watch@yahoo.com> wrote:
                                        >
                                        >
                                        >
                                        >
                                        >
                                        >
                                        > All this talk about the compression wave...I forgot to say that I observed
                                        > it last weekend with Sam Houston's 24" Dob. The compression wave you talk
                                        > about was visible in the eyepiece, rather easily...I hope to get another
                                        > crack at it tonight...our last labs at the observatory for the semester are
                                        > this week, so soon I'll have the observatory almost entirely to myself
                                        > again.
                                        >
                                        >
                                        > anjal_sharma@yahoo.com wrote:
                                        >
                                        >
                                        >
                                        >
                                        >
                                        > Kelsey,
                                        >
                                        > Did you adjust the color weights on the R, G and B channels? You have to do
                                        > this to account for different spectral transmission areas by the filters at
                                        > the three primary colors and also for some spectral overlap between the B
                                        > and G filters and a gap in the spectrum between the G and R filters. Here's
                                        > an attachment which shows how the L R G abd B filters in your Meade filter
                                        > set behave. You can get a good guess as to color weight by using these
                                        > spectra.
                                        >
                                        > Also note the native spectra of the G and R filters. They let in
                                        > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                                        > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                                        > with your reflector, your ED80 and my Sky90 are apochromats and not
                                        > super-apochromats. They cannot focus the UV and IR light at the same point
                                        > as visible wavelengths.
                                        >
                                        > Therefore, unless you screw in the L filter which is the IR block filter in
                                        > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                                        > you're going to get slightly bloated stars in the LRGB image and perhaps a
                                        > bit of residual chroma as these UV and IR wavelengths will mix in with the
                                        > B, G and R wavelengths.
                                        >
                                        > Anjal.
                                        >
                                        >
                                        > ----- Original Message ----
                                        > From: Don E. Bray <debray1@mac.com>
                                        > To: brazosastro@yahoogroups.com
                                        > Sent: Tuesday, November 6, 2007 2:59:18 PM
                                        > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                                        >
                                        >
                                        >
                                        > Kelsey,
                                        >
                                        >
                                        > You are right, it is there. The difference in image density is subtle, but
                                        > if you look at it correctly, that outward leading front is unmistakably
                                        > there.
                                        >
                                        >
                                        > Good work.
                                        >
                                        >
                                        > Don
                                        >
                                        >
                                        >
                                        > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                                        >
                                        >
                                        >
                                        >
                                        >
                                        > Don and Anjal,
                                        >
                                        > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                                        > I'm kind of new to RGB processing and mine came out a much differen't color
                                        > than most of the images of Holmes that I've seen. Either the focus or the
                                        > exposure of the luminosity channel could've used some adjustment as well. At
                                        > any rate, you can see the same issues as you describe in my photo as well.
                                        >
                                        > Kelsey
                                        >
                                        >
                                        > On 11/6/07, Don E. Bray <debray1@mac.com> wrote:
                                        > >
                                        > >
                                        > >
                                        > >
                                        > >
                                        > > Anjal et al.,
                                        > >
                                        > >
                                        > > It also shows up in Mark's photo, but not in the others. The physical
                                        > effect is most likely due to the flow of this projectile in the whatever
                                        > atmosphere it is encountering. Been a few years since I did fluid flow work
                                        > related to projectiles, but the leading compressional wave and then a drop
                                        > off is consistent with other photos that I have seen in bullet and airplane
                                        > wind tunnel shots. So, it must be physically there. Also, one could deduce
                                        > something about the properties of the atmosphere that it is encountering by
                                        > measuring the spacing between light and dark areas and the comet body. But,
                                        > I expect that real astrophysicists have already done that.
                                        > >
                                        > >
                                        > > Note that it does not show up in the other photos, at least it is not as
                                        > obvious. This is possible due to Photoshop processing. But these photos
                                        > where the compression wave is not shown emphasize the actual solid body of
                                        > the comet, so they are all part of a complete information package.
                                        > >
                                        > >
                                        > > Thanks, for your comment. This is all very interesting.
                                        > >
                                        > >
                                        > > Don
                                        > >
                                        > >
                                        > >
                                        > > On 5 Nov 2007, at 10:29 PM, anjal_sharma wrote:
                                        > >
                                        > >
                                        > >
                                        > >
                                        > >
                                        > > Don,
                                        > >
                                        > > My DSI LRGB image of Holmes taken on Nov 2 shows the same leading
                                        > > compression wave and pressure drop type effect too. I don't think it
                                        > > is an artifact.
                                        > >
                                        > > Anjal.
                                        > >
                                        > > --- In brazosastro@ yahoogroups.com , "debclltx" <debray1@...> wrote:
                                        > > >
                                        > > > Gotta be careful to not creat effects that don't exist, but my recent
                                        > > photo of Holmes when
                                        > > > edited in Photoshop appears to show a leading compression wave and
                                        > > then a pressure drop
                                        > > > immediately behind it. This assumed that the comet is going to the
                                        > > right. Any comments?
                                        > > >
                                        > > > Don
                                        > > >
                                        > >
                                        > >
                                        > >
                                        > >
                                        > >
                                        > >
                                        > > **** Note change in telephone numbers ****
                                        > > Don E. Bray, Ph.D., P. E.
                                        > > Don E. Bray, Inc.
                                        > > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                        > > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                        > > USA
                                        > > Office/Cellular 979-492-9534
                                        > > Fax 979-693-1620
                                        > > Res 979-693-1620
                                        > > debray1@mac.com
                                        > > debray1@brayengr.com
                                        > > < http://brayengr.com>Astronomy photos
                                        > http://homepage.mac.com/debray1/PhotoAlbum22.html
                                        > >
                                        > >
                                        >
                                        >
                                        >
                                        >
                                        >
                                        >
                                        > **** Note change in telephone numbers ****
                                        > Don E. Bray, Ph.D., P. E.
                                        > Don E. Bray, Inc.
                                        > Mail P. O. Box 10315, College Station, Texas 77842-0315
                                        > Ship 1601 Fontaine Street, College Station, Texas 77845-5612
                                        > USA
                                        > Office/Cellular 979-492-9534
                                        > Fax 979-693-1620
                                        > Res 979-693-1620
                                        > debray1@mac. com
                                        > debray1@brayengr. com
                                        > <http://brayengr. com>Astronomy photos http://homepage. mac.com/debray1/
                                        > PhotoAlbum22. html
                                        >
                                        >
                                        >
                                        > __________________________________________________
                                        > Do You Yahoo!?
                                        > Tired of spam? Yahoo! Mail has the best spam protection around
                                        > http://mail.yahoo.com
                                        >
                                        >
                                        >
                                        > __________________________________________________
                                        > Do You Yahoo!?
                                        > Tired of spam? Yahoo! Mail has the best spam protection around
                                        > http://mail.yahoo.com
                                        >
                                        >

                                        (Message over 64 KB, truncated)
                                      • Don E. Bray
                                        Thanks, Mike, for researching this. That is certainly a reasonable explanation, and makes these photos all the more significant. don . ... **** Note change in
                                        Message 19 of 19 , Nov 8, 2007
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                                          Thanks, Mike, for researching this. That is certainly a reasonable explanation, and makes these photos all the more significant.

                                          don
                                          .
                                          On 8 Nov 2007, at 9:49 AM, Michael Prokosch wrote:

                                          yes, that is what is most likely is.  Some of it is outgassing that has taken place after the explosion, but at least a portion of it is from the explosion itself. 

                                          Karl Williams <engineer_kc5ixx@yahoo.com> wrote:

                                          Forgive my ignorance here, but is this compression wave that same phemonon that is being reported as debris from an explosion on the comet (NASA & CNN) that suddenly made the comet visible to the naked eye?
                                           
                                          Karl

                                          "Don E. Bray" <debray1@mac.com> wrote:
                                          Maybe I need to add a little more. The compression wave is at the very front of the disturbance, leading the comet "rock" by some distance. This area is slightly lighter than the rest. Then, as you travel back toward the rock the appearance becomes slightly darker, indicating a change in pressure and density. There are variations as you go toward the comet itself until you see a very thin layer at the very front of the comet. This is all traveling at the speed of the comet. 

                                          Don

                                          On 7 Nov 2007, at 4:39 PM, Don E. Bray wrote:

                                          The subtle changes that we see at the leading edge are caused by differences in the density and the associated  light speed of the material, hence there are differences in the diffraction of the light coming from the comet.  This effect continues right up to the edge of the "rock" as well as the trailing tail.

                                          Don



                                          On 7 Nov 2007, at 4:29 PM, Kelsey Golden wrote:

                                          Michael,

                                          What a great job you have!

                                          About the compression wave, have we ruled out the possibility that
                                          it's just an optical illusion created by the angle at which we are
                                          ! viewing the comet? Forgive me for being ignorant but are comets
                                          supposed to have a compression wave?

                                          Kelsey

                                          On Nov 7, 2007 3:37 PM, Michael Prokosch <star2_watch@yahoo.com> wrote:
                                          >
                                          >
                                          >
                                          >
                                          >
                                          >
                                          > All this talk about the compression wave...I forgot to say that I observed
                                          > it last weekend with Sam Houston's 24" Dob. The compression wave you talk
                                          > about was visible in the eyepiece, rather easily...I hope to get another
                                          > crack at it tonight...our last labs at the observatory for the semester are
                                          > this week, so soon I'll have the observatory almost entirely to myself
                                          > again.
                                          >
                                          >
                                          > anjal_sharma@yahoo.com wrote:
                                          >
                                          >
                                          >
                                          >
                                          >
                                          > Kelsey,
                                          >
                                          > Did you adjust the color weights on the R, G and B channels? You have to do
                                          > this to account for different spectral transmission areas by the filters at
                                          > the three primary colors and also for some spectral overlap between the B
                                          > and G filters and a gap in the spectrum between the G and R filters. Here's
                                          > an attachment which shows how the L R G abd B filters in your Meade filter
                                          > set behave. You can get a good guess as to color weight by using these
                                          > spectra.
                                          >
                                          > Also note the native spectra of the G and R filters. They let in
                                          > SIGNIFICANT amounts of IR light. Note also the native spectrum of the B
                                          > filter. It lets in SIGNIFICANT amounts of UV light. Although not a problem
                                          > with your reflector, your ED80 and my Sky90 are apochromats and not
                                          > super-apochromats. They cannot focus the UV and IR light at the same point
                                          > as visible wavelengths.
                                          >
                                          > Therefore, unless you screw in the L filter which is the IR block filter in
                                          > the nosepiece of your DSI camera which is sensitive well into the UV and IR,
                                          > you're going to get slightly bloated stars in the LRGB image and perhaps a
                                          > bit of residual chroma as these UV and IR wavelengths will mix in with the
                                          > B, G and R wavelengths.
                                          >
                                          > Anjal.
                                          >
                                          >
                                          > ----- Original Message ----
                                          > From: Don E. Bray <debray1@mac.com>
                                          > To: brazosastro@yahoogroups.com
                                          > Sent: Tuesday, November 6, 2007 2:59:18 PM
                                          > Subject: Re: [brazosastro] Re: Comet Holmes leading compresion wave
                                          >
                                          >
                                          >
                                          > Kelsey,
                                          >
                                          >
                                          > You are right, it is there. The difference in image density is subtle, but
                                          > if you look at it correctly, that outward leading front is unmistakably
                                          > there.
                                          >
                                          >
                                          > Good work.
                                          >
                                          >
                                          > Don
                                          >
                                          >
                                          >
                                          > On 6 Nov 2007, at 11:40 AM, Kelsey Golden wrote:
                                          >
                                          >
                                          >
                                          >
                                          >
                                          > Don and Anjal,
                                          >
                                          > I just put up my latest LRGB image of Holmes which was also taken on 11/02.
                                          > I'm kind of new to RGB processing and mine came out a much differen't color
                                          > than most of the images of Holmes that I've seen. Either the focus or the
                                          > exposure of the luminosity channel could've used some adjustment as well. At
                                          > any rate, you can see the same issues as you describe in my photo as well.
                                          >
                                          > Kelsey
                                          >
                                          >
                                          > On 11/6/07, Don E. Bray <debray1@mac.com> wrote:
                                          > >
                                          > >
                                          > >
                                          > >
                                          > >
                                          > > Anjal et al.,
                                          > >
                                          > >
                                          > > It also shows up in Mark's photo, but not in the others. The physical
                                          > effect is most likely due to the flow of this projectile in the whatever
                                          > atmosphere it is encountering. Been a few years since I did fluid flow work
                                          > related to projectiles, but the leading compressional wave and then a drop
                                          > off is consistent with other photos that I have seen in bullet and airplane
                                          > wind tunnel shots. So, it must be physically there. Also, one could deduce
                                          > something about the properties of the atmosphere that it is encountering by
                                          > measuring the spacing between light and dark areas and the comet body. But,
                                          > I expect that real astrophysicists have already done that.
                                          > >
                                          > >
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