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imaging/guiding question from a new member

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  • mcpark1@yahoo.com
    Hello, I am joining this group because I have had a hard time getting assistance from the SBIG group. It seems that you have to be a pro before most of the
    Message 1 of 23 , Oct 26, 2001
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      Hello,

      I am joining this group because I have had a hard time getting
      assistance from the SBIG group. It seems that you have to be a pro
      before most of the people on that group give you a second look. One
      person on that list did suggest I try this list, since your main
      focus is to help novices like myself get through the learning curve.

      Here is my current issue...

      I have a Celestron C8 on a Losmandy GM8 mount. I want to image with
      one PIXCEL 255 using a FOCAL REDUCER LENS (the one that slides into
      the nose of the 255 and has a collar to get F3.75) and an external
      color wheel. I attach this to my Celestron off-axis guider and want
      to autoguide with the other PIXCEL 255 in the guiding tube on the off-
      axis-guider (operating at F10). The problem is that the guiding 255
      needs to be about 1 foot away from the off-axis-guider to be in
      focus. This is caused by the different focal lengths of the two
      CCDs. I would like to operate the CCDs at the different focal
      lengths so my guiding can be more precise. However, putting the
      guiding CCD so far out, cause too much torque and the OAG slips. Can
      anyone recommend a setup that will allow me to color image at F3.7
      while guiding at F10. NOTE: purchasing expensive equipment like an
      internal color wheel is not currently an option. I do have a
      Celestron focal reducer that I could use, but it would put the
      guiding CCD at f6.7 as well as the imagining CCD.

      Any suggestions, or am I just trying to do the impossible

      Another possibility is to lock down the C8 mirror and us a guide
      scope. I have considered this, but need precise instructions on how
      to correctly drill the C8 for a locking screw. The last thing I want
      to do is ruin my scope! If anyone has any instructions on how to do
      this, please let me know.


      Thank you in advance for you assistance.
    • Brady Johnson
      A separate guide scope is likely your best option if you want to work a different focal lengths, unless you want to build an extension tube. I m sure you d be
      Message 2 of 23 , Oct 26, 2001
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        A separate guide scope is likely your best option if you want to work a different focal lengths, unless you want to build an extension tube. I'm sure you'd be much happier mounting an inexpensive refractor on your 8" and guide with that. A long extension tube on your off-axis guider would work like a lever and the whole assembly would be prone to rotating.

        As for locking down the mirror, I think that's probably optional. The main point of the locking is to prevent mirror flops that will occur as you cross the meridian - that is, as your pointing switches from East to West. You can easily avoid mirror flop by not imaging across the meridian.

        I also think that in many cases there is too much concern over focal lengths for guide scopes, and that a lot of this concern is a carry over from film-based astrophotography. Here's how I understand it to be.

        With CCDs you can achieve subpixel resolution while autoguiding. If your guider and imager are operating at the same focal length, then you would also get subpixel *variation* on your imaging chip. More specifically, a point source on your imaging chip would never leave the boundaries of a single pixel (assuming your mount/guider operate properly). On film, variation in the position of a point source over an area the size of a CCD pixel could well ruin the image. With the CCD, you wouldn't even know there had been variation in the pointing, since all light was confined to the pixel.

        I have seen outstanding images selfguided with focal lengths as short as F = 50mm! There are many outstanding images on the SBIG list taken by people using camera lenses with F ranging from 50 to 400mm. These are selfguided images, meaning the same (short) focal length is used for guiding and imaging, and the results are often astonishing.

        For your situation, at f/6.3 on an 8" scope you're somewhere in the F = 1250mm range. That's plenty of F for guiding! Consequently, your best solution might be to use your Celestron focal reducer and image and guide at f/6.3

        One last comment. I too am a relative beginner. Much of what I have learned and have been able to share with you has come from assistance I've received either directly - or simply picked up by monitoring - the SBIG group. I appreciate your frustration in trying to get things to work. But I think your comments about that group are completely unwarranted.

        Hope this helps.


        Brady Johnson


        ----- Original Message -----
        From: mcpark1@...
        To: ccd-newastro@yahoogroups.com
        Sent: Friday, October 26, 2001 8:13 AM
        Subject: [ccd-newastro] imaging/guiding question from a new member


        Hello,

        I am joining this group because I have had a hard time getting
        assistance from the SBIG group. It seems that you have to be a pro
        before most of the people on that group give you a second look. One
        person on that list did suggest I try this list, since your main
        focus is to help novices like myself get through the learning curve.

        Here is my current issue...

        I have a Celestron C8 on a Losmandy GM8 mount. I want to image with
        one PIXCEL 255 using a FOCAL REDUCER LENS (the one that slides into
        the nose of the 255 and has a collar to get F3.75) and an external
        color wheel. I attach this to my Celestron off-axis guider and want
        to autoguide with the other PIXCEL 255 in the guiding tube on the off-
        axis-guider (operating at F10). The problem is that the guiding 255
        needs to be about 1 foot away from the off-axis-guider to be in
        focus. This is caused by the different focal lengths of the two
        CCDs. I would like to operate the CCDs at the different focal
        lengths so my guiding can be more precise. However, putting the
        guiding CCD so far out, cause too much torque and the OAG slips. Can
        anyone recommend a setup that will allow me to color image at F3.7
        while guiding at F10. NOTE: purchasing expensive equipment like an
        internal color wheel is not currently an option. I do have a
        Celestron focal reducer that I could use, but it would put the
        guiding CCD at f6.7 as well as the imagining CCD.

        Any suggestions, or am I just trying to do the impossible

        Another possibility is to lock down the C8 mirror and us a guide
        scope. I have considered this, but need precise instructions on how
        to correctly drill the C8 for a locking screw. The last thing I want
        to do is ruin my scope! If anyone has any instructions on how to do
        this, please let me know.


        Thank you in advance for you assistance.




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        [Non-text portions of this message have been removed]
      • Ugly Dog
        ... I respectfully disagree. I ve been on SBIG-USER for almost six years (since before SBIG started running it themselves) and it is not a beginner friendly
        Message 3 of 23 , Oct 26, 2001
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          --- Brady Johnson <bradydjohnson@...> wrote:
          >> One last comment. I too am a relative beginner. Much of what I
          > have learned and have been able to share with you has come from
          > assistance I've received either directly - or simply picked up
          > by monitoring - the SBIG group. I appreciate your frustration
          > in trying to get things to work. But I think your comments
          > about that group are completely unwarranted.
          >

          I respectfully disagree. I've been on SBIG-USER for almost six
          years (since before SBIG started running it themselves) and it is
          not a beginner friendly atmosphere. However it does keep changing
          in character, so I'm still hopefull!


          =====
          Ugly Dog
          http://www.bewellweb.com/g42016k/astro.htm
        • Brady Johnson
          That hasn t been my experience. But I m certainly not against making it more user friendly, either. ... From: Ugly Dog To: ccd-newastro@yahoogroups.com Sent:
          Message 4 of 23 , Oct 26, 2001
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            That hasn't been my experience. But I'm certainly not against making it more user friendly, either.
            ----- Original Message -----
            From: Ugly Dog
            To: ccd-newastro@yahoogroups.com
            Sent: Friday, October 26, 2001 3:54 PM
            Subject: Re: [ccd-newastro] imaging/guiding question from a new member



            --- Brady Johnson <bradydjohnson@...> wrote:
            >> One last comment. I too am a relative beginner. Much of what I
            > have learned and have been able to share with you has come from
            > assistance I've received either directly - or simply picked up
            > by monitoring - the SBIG group. I appreciate your frustration
            > in trying to get things to work. But I think your comments
            > about that group are completely unwarranted.
            >

            I respectfully disagree. I've been on SBIG-USER for almost six
            years (since before SBIG started running it themselves) and it is
            not a beginner friendly atmosphere. However it does keep changing
            in character, so I'm still hopefull!


            =====
            Ugly Dog
            http://www.bewellweb.com/g42016k/astro.htm

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            [Non-text portions of this message have been removed]
          • _kevin1231@excite.com
            I would also agree somewhat with ugly, A great sorce of information and seem to be a great bunch of people but there is some excess astro geek testosterone in
            Message 5 of 23 , Oct 27, 2001
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              I would also agree somewhat with ugly, A great sorce of information
              and seem to be a great bunch of people but there is some excess astro
              geek testosterone in that forum.

              Kevin

              --- In ccd-newastro@y..., Ugly Dog <shenzistiber@y...> wrote:
              >
              > --- Brady Johnson <bradydjohnson@h...> wrote:
              > >> One last comment. I too am a relative beginner. Much of what I
              > > have learned and have been able to share with you has come from
              > > assistance I've received either directly - or simply picked up
              > > by monitoring - the SBIG group. I appreciate your frustration
              > > in trying to get things to work. But I think your comments
              > > about that group are completely unwarranted.
              > >
              >
              > I respectfully disagree. I've been on SBIG-USER for almost six
              > years (since before SBIG started running it themselves) and it is
              > not a beginner friendly atmosphere. However it does keep changing
              > in character, so I'm still hopefull!
              >
              >
              > =====
              > Ugly Dog
              > http://www.bewellweb.com/g42016k/astro.htm
            • Ron Wodaski
              That s one way to describe it. I try to mellow that forum out by providing actual practical experience. On the plus side, there is some serious imaging
              Message 6 of 23 , Oct 27, 2001
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                That's one way to describe it. I try to mellow that forum out by providing
                actual practical experience. On the plus side, there is some serious imaging
                horsepower among contributors there, and if you sift through it you will
                come up with some gems.

                Ron Wodaski
                The New CCD Astronomy
                http://www.newastro.com

                -----Original Message-----
                From: _kevin1231@... [mailto:_kevin1231@...]
                Sent: Saturday, October 27, 2001 9:21 AM
                To: ccd-newastro@yahoogroups.com
                Subject: [ccd-newastro] Re: imaging/guiding question from a new member


                I would also agree somewhat with ugly, A great sorce of information
                and seem to be a great bunch of people but there is some excess astro
                geek testosterone in that forum.

                Kevin

                --- In ccd-newastro@y..., Ugly Dog <shenzistiber@y...> wrote:
                >
                > --- Brady Johnson <bradydjohnson@h...> wrote:
                > >> One last comment. I too am a relative beginner. Much of what I
                > > have learned and have been able to share with you has come from
                > > assistance I've received either directly - or simply picked up
                > > by monitoring - the SBIG group. I appreciate your frustration
                > > in trying to get things to work. But I think your comments
                > > about that group are completely unwarranted.
                > >
                >
                > I respectfully disagree. I've been on SBIG-USER for almost six
                > years (since before SBIG started running it themselves) and it is
                > not a beginner friendly atmosphere. However it does keep changing
                > in character, so I'm still hopefull!
                >
                >
                > =====
                > Ugly Dog
                > http://www.bewellweb.com/g42016k/astro.htm



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                ccd-newastro-unsubscribe@egroups.com



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              • _kevin1231@excite.com
                ... your guider and imager are operating at the same focal length, then you would also get subpixel *variation* on your imaging chip. More specifically, a
                Message 7 of 23 , Oct 27, 2001
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                  --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...> wrote:
                  >
                  > With CCDs you can achieve subpixel resolution while autoguiding. If
                  your guider and imager are operating at the same focal length, then
                  you would also get subpixel *variation* on your imaging chip. More
                  specifically, a point source on your imaging chip would never leave
                  the boundaries of a single pixel (assuming your mount/guider operate
                  properly). On film, variation in the position of a point source over
                  an area the size of a CCD pixel could well ruin the image. With the
                  CCD, you wouldn't even know there had been variation in the pointing,
                  since all light was confined to the pixel.
                  >

                  Brady,

                  I was hoping you could explain above a bit more as I don't
                  understand. I thought film was more forgiving than CCD. I have
                  heard many people claim a particular mount is good astrophotography
                  platform, but not good enough for CCD which "demands more". If your
                  guiding at f10 with modest size pixels you would get drift of less
                  than a pixel, which would cover a couple arcseconds. This would show
                  up on film, but not another ccd? In theory I guess this makes sense
                  in that film should have finer resolution than ccd. Does this
                  support my thinking that a film based image can actually show much
                  more detail than CCD? Though most Great CCD images I see (high
                  resolution galactic type) by Ron, robert adam ect, blow away most
                  anything I have seen on film. But I still give the widefield not to
                  film as the images are just so much more pleasing.

                  Kevin
                • Ron Wodaski
                  Historically, the pixel size of film has been considered to be around 25 microns. That s substantially larger than many of today s cameras. So, in general,
                  Message 8 of 23 , Oct 27, 2001
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                    Historically, the "pixel size" of film has been considered to be around 25
                    microns. That's substantially larger than many of today's cameras. So, in
                    general, it is reasonable to assume that CCD is higher resolution that film,
                    and therefore more demanding.

                    Strictly speaking, of course, film has a grain size, not a pixel size, but
                    other than the non-orthogonality of the grains, this turns out to be useful
                    anyway.

                    There are some films that have a higher resolution than this. For example,
                    hypered Tech Pan has about as high a film resolution as you are going to
                    find, yet I can duplicate with a 4" 9-micron CCD the same resolution you can
                    get with a much larger instrument using Tech Pan. Have never worked out the
                    numbers, but my conclusion is that CCD pixels are much smaller than film
                    grains.

                    It's also worth addressing what "sub pixel guiding" really means. With an
                    STV, the math is sophisticated enough to centroid a star down to about
                    1/30th of a pixel. This means that you can guide down to 0.2 arcseconds with
                    only a 500mm guidescope. So there is really no need to use a longer
                    guidescope with the STV. At 500mm, you can ensure the accuracy and
                    flexibility of guiding by using a fast (f/4, f/5, f/6) guidescope.

                    It is a mistake to think of stars "covering a pixel" or staying within the
                    domain of a pixel. Atmospheric turbulence almost always smears the image.
                    Even Adam Block's recent images from Kitt Peak, which are taken at f/10 on a
                    16" LX200 with the 9-micron pixels of an ST-8, for 0.438 arcseconds per
                    pixel image scale, clearly show mag 20 stars covering many pixels. At the
                    other extreme, a 50mm lens and an ST-8E, at about 40 arcseconds per pixel,
                    still show round stars covering multiple pixels.

                    I have found that it is best to verify theories with some practical testing.
                    The actual physics of CCD imaging has shaken many a working hypothesis. <G>

                    Ron Wodaski
                    The New CCD Astronomy
                    http://www.newastro.com

                    -----Original Message-----
                    From: _kevin1231@... [mailto:_kevin1231@...]
                    Sent: Saturday, October 27, 2001 9:39 AM
                    To: ccd-newastro@yahoogroups.com
                    Subject: [ccd-newastro] Re: imaging/guiding question from a new member


                    --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...> wrote:
                    >
                    > With CCDs you can achieve subpixel resolution while autoguiding. If
                    your guider and imager are operating at the same focal length, then
                    you would also get subpixel *variation* on your imaging chip. More
                    specifically, a point source on your imaging chip would never leave
                    the boundaries of a single pixel (assuming your mount/guider operate
                    properly). On film, variation in the position of a point source over
                    an area the size of a CCD pixel could well ruin the image. With the
                    CCD, you wouldn't even know there had been variation in the pointing,
                    since all light was confined to the pixel.
                    >

                    Brady,

                    I was hoping you could explain above a bit more as I don't
                    understand. I thought film was more forgiving than CCD. I have
                    heard many people claim a particular mount is good astrophotography
                    platform, but not good enough for CCD which "demands more". If your
                    guiding at f10 with modest size pixels you would get drift of less
                    than a pixel, which would cover a couple arcseconds. This would show
                    up on film, but not another ccd? In theory I guess this makes sense
                    in that film should have finer resolution than ccd. Does this
                    support my thinking that a film based image can actually show much
                    more detail than CCD? Though most Great CCD images I see (high
                    resolution galactic type) by Ron, robert adam ect, blow away most
                    anything I have seen on film. But I still give the widefield not to
                    film as the images are just so much more pleasing.

                    Kevin



                    To unsubscribe from this group, send an email to:
                    ccd-newastro-unsubscribe@egroups.com



                    Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                  • _kevin1231@excite.com
                    Ron, Thanks for the reply. I unfortunately am back to not understanding Bradys comments. Are they accurate? I would think sub pixel guiding would be far
                    Message 9 of 23 , Oct 27, 2001
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                      Ron,
                      Thanks for the reply. I unfortunately am back to not understanding
                      Bradys comments. Are they accurate? I would think sub pixel guiding
                      would be far more than enough for a film image. I have taken what
                      seem to be sharp images (albeit short) unguided at F10 for several
                      minutes. Much, much longer than the sometimes 15 seconds I can get
                      when imaging at .5" per pixel.

                      I am also familiar with beauty of sub pixel guiding. Tried out an
                      STV and could not believe I can guide with a camera lens while
                      imaging on CCD.

                      Can you rephrase his comments if correct, so that I can understand
                      what he means?

                      Thanks,
                      Kevin


                      --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                      > Historically, the "pixel size" of film has been considered to be
                      around 25
                      > microns. That's substantially larger than many of today's cameras.
                      So, in
                      > general, it is reasonable to assume that CCD is higher resolution
                      that film,
                      > and therefore more demanding.
                      >
                      > Strictly speaking, of course, film has a grain size, not a pixel
                      size, but
                      > other than the non-orthogonality of the grains, this turns out to
                      be useful
                      > anyway.
                      >
                      > There are some films that have a higher resolution than this. For
                      example,
                      > hypered Tech Pan has about as high a film resolution as you are
                      going to
                      > find, yet I can duplicate with a 4" 9-micron CCD the same
                      resolution you can
                      > get with a much larger instrument using Tech Pan. Have never worked
                      out the
                      > numbers, but my conclusion is that CCD pixels are much smaller than
                      film
                      > grains.
                      >
                      > It's also worth addressing what "sub pixel guiding" really means.
                      With an
                      > STV, the math is sophisticated enough to centroid a star down to
                      about
                      > 1/30th of a pixel. This means that you can guide down to 0.2
                      arcseconds with
                      > only a 500mm guidescope. So there is really no need to use a longer
                      > guidescope with the STV. At 500mm, you can ensure the accuracy and
                      > flexibility of guiding by using a fast (f/4, f/5, f/6) guidescope.
                      >
                      > It is a mistake to think of stars "covering a pixel" or staying
                      within the
                      > domain of a pixel. Atmospheric turbulence almost always smears the
                      image.
                      > Even Adam Block's recent images from Kitt Peak, which are taken at
                      f/10 on a
                      > 16" LX200 with the 9-micron pixels of an ST-8, for 0.438 arcseconds
                      per
                      > pixel image scale, clearly show mag 20 stars covering many pixels.
                      At the
                      > other extreme, a 50mm lens and an ST-8E, at about 40 arcseconds per
                      pixel,
                      > still show round stars covering multiple pixels.
                      >
                      > I have found that it is best to verify theories with some practical
                      testing.
                      > The actual physics of CCD imaging has shaken many a working
                      hypothesis. <G>
                      >
                      > Ron Wodaski
                      > The New CCD Astronomy
                      > http://www.newastro.com
                      >
                      > -----Original Message-----
                      > From: _kevin1231@e... [mailto:_kevin1231@e...]
                      > Sent: Saturday, October 27, 2001 9:39 AM
                      > To: ccd-newastro@y...
                      > Subject: [ccd-newastro] Re: imaging/guiding question from a new
                      member
                      >
                      >
                      > --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...>
                      wrote:
                      > >
                      > > With CCDs you can achieve subpixel resolution while autoguiding.
                      If
                      > your guider and imager are operating at the same focal length, then
                      > you would also get subpixel *variation* on your imaging chip. More
                      > specifically, a point source on your imaging chip would never leave
                      > the boundaries of a single pixel (assuming your mount/guider operate
                      > properly). On film, variation in the position of a point source over
                      > an area the size of a CCD pixel could well ruin the image. With the
                      > CCD, you wouldn't even know there had been variation in the
                      pointing,
                      > since all light was confined to the pixel.
                      > >
                      >
                      > Brady,
                      >
                      > I was hoping you could explain above a bit more as I don't
                      > understand. I thought film was more forgiving than CCD. I have
                      > heard many people claim a particular mount is good astrophotography
                      > platform, but not good enough for CCD which "demands more". If your
                      > guiding at f10 with modest size pixels you would get drift of less
                      > than a pixel, which would cover a couple arcseconds. This would
                      show
                      > up on film, but not another ccd? In theory I guess this makes sense
                      > in that film should have finer resolution than ccd. Does this
                      > support my thinking that a film based image can actually show much
                      > more detail than CCD? Though most Great CCD images I see (high
                      > resolution galactic type) by Ron, robert adam ect, blow away most
                      > anything I have seen on film. But I still give the widefield not to
                      > film as the images are just so much more pleasing.
                      >
                      > Kevin
                      >
                      >
                      >
                      > To unsubscribe from this group, send an email to:
                      > ccd-newastro-unsubscribe@egroups.com
                      >
                      >
                      >
                      > Your use of Yahoo! Groups is subject to
                      http://docs.yahoo.com/info/terms/
                    • Ron Wodaski
                      Actually, I don t agree with what Brady said. I was trying to state a different case in my earlier message. As far as I know, most CCD cameras are going to
                      Message 10 of 23 , Oct 27, 2001
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                        Actually, I don't agree with what Brady said. I was trying to state a
                        different case in my earlier message. As far as I know, most CCD cameras are
                        going to provide higher resolution and a smaller FOV than film.

                        Ron Wodaski
                        The New CCD Astronomy
                        http://www.newastro.com

                        -----Original Message-----
                        From: _kevin1231@... [mailto:_kevin1231@...]
                        Sent: Saturday, October 27, 2001 11:37 AM
                        To: ccd-newastro@yahoogroups.com
                        Subject: [ccd-newastro] Re: imaging/guiding question from a new member


                        Ron,
                        Thanks for the reply. I unfortunately am back to not understanding
                        Bradys comments. Are they accurate? I would think sub pixel guiding
                        would be far more than enough for a film image. I have taken what
                        seem to be sharp images (albeit short) unguided at F10 for several
                        minutes. Much, much longer than the sometimes 15 seconds I can get
                        when imaging at .5" per pixel.

                        I am also familiar with beauty of sub pixel guiding. Tried out an
                        STV and could not believe I can guide with a camera lens while
                        imaging on CCD.

                        Can you rephrase his comments if correct, so that I can understand
                        what he means?

                        Thanks,
                        Kevin


                        --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                        > Historically, the "pixel size" of film has been considered to be
                        around 25
                        > microns. That's substantially larger than many of today's cameras.
                        So, in
                        > general, it is reasonable to assume that CCD is higher resolution
                        that film,
                        > and therefore more demanding.
                        >
                        > Strictly speaking, of course, film has a grain size, not a pixel
                        size, but
                        > other than the non-orthogonality of the grains, this turns out to
                        be useful
                        > anyway.
                        >
                        > There are some films that have a higher resolution than this. For
                        example,
                        > hypered Tech Pan has about as high a film resolution as you are
                        going to
                        > find, yet I can duplicate with a 4" 9-micron CCD the same
                        resolution you can
                        > get with a much larger instrument using Tech Pan. Have never worked
                        out the
                        > numbers, but my conclusion is that CCD pixels are much smaller than
                        film
                        > grains.
                        >
                        > It's also worth addressing what "sub pixel guiding" really means.
                        With an
                        > STV, the math is sophisticated enough to centroid a star down to
                        about
                        > 1/30th of a pixel. This means that you can guide down to 0.2
                        arcseconds with
                        > only a 500mm guidescope. So there is really no need to use a longer
                        > guidescope with the STV. At 500mm, you can ensure the accuracy and
                        > flexibility of guiding by using a fast (f/4, f/5, f/6) guidescope.
                        >
                        > It is a mistake to think of stars "covering a pixel" or staying
                        within the
                        > domain of a pixel. Atmospheric turbulence almost always smears the
                        image.
                        > Even Adam Block's recent images from Kitt Peak, which are taken at
                        f/10 on a
                        > 16" LX200 with the 9-micron pixels of an ST-8, for 0.438 arcseconds
                        per
                        > pixel image scale, clearly show mag 20 stars covering many pixels.
                        At the
                        > other extreme, a 50mm lens and an ST-8E, at about 40 arcseconds per
                        pixel,
                        > still show round stars covering multiple pixels.
                        >
                        > I have found that it is best to verify theories with some practical
                        testing.
                        > The actual physics of CCD imaging has shaken many a working
                        hypothesis. <G>
                        >
                        > Ron Wodaski
                        > The New CCD Astronomy
                        > http://www.newastro.com
                        >
                        > -----Original Message-----
                        > From: _kevin1231@e... [mailto:_kevin1231@e...]
                        > Sent: Saturday, October 27, 2001 9:39 AM
                        > To: ccd-newastro@y...
                        > Subject: [ccd-newastro] Re: imaging/guiding question from a new
                        member
                        >
                        >
                        > --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...>
                        wrote:
                        > >
                        > > With CCDs you can achieve subpixel resolution while autoguiding.
                        If
                        > your guider and imager are operating at the same focal length, then
                        > you would also get subpixel *variation* on your imaging chip. More
                        > specifically, a point source on your imaging chip would never leave
                        > the boundaries of a single pixel (assuming your mount/guider operate
                        > properly). On film, variation in the position of a point source over
                        > an area the size of a CCD pixel could well ruin the image. With the
                        > CCD, you wouldn't even know there had been variation in the
                        pointing,
                        > since all light was confined to the pixel.
                        > >
                        >
                        > Brady,
                        >
                        > I was hoping you could explain above a bit more as I don't
                        > understand. I thought film was more forgiving than CCD. I have
                        > heard many people claim a particular mount is good astrophotography
                        > platform, but not good enough for CCD which "demands more". If your
                        > guiding at f10 with modest size pixels you would get drift of less
                        > than a pixel, which would cover a couple arcseconds. This would
                        show
                        > up on film, but not another ccd? In theory I guess this makes sense
                        > in that film should have finer resolution than ccd. Does this
                        > support my thinking that a film based image can actually show much
                        > more detail than CCD? Though most Great CCD images I see (high
                        > resolution galactic type) by Ron, robert adam ect, blow away most
                        > anything I have seen on film. But I still give the widefield not to
                        > film as the images are just so much more pleasing.
                        >
                        > Kevin
                        >
                        >
                        >
                        > To unsubscribe from this group, send an email to:
                        > ccd-newastro-unsubscribe@egroups.com
                        >
                        >
                        >
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                      • Brady Johnson
                        Hi Kevin: I see Ron has posted a nice response to this. I d like to add a couple of thoughts too. First, I should give you some background. I am a novice at
                        Message 11 of 23 , Oct 27, 2001
                        • 0 Attachment
                          Hi Kevin:

                          I see Ron has posted a nice response to this. I'd like to add a couple of thoughts too.

                          First, I should give you some background. I am a novice at imaging. Most of my imaging so far is being done with 9 micron pixels using 50 - 200mm camera lenses attached to an ST8/CFW8. I often selfguide my exposures, so the guide chip (which has slightly larger pixels) is using the same optics.

                          The corrections I see during the self guide sessions rarely exceed 0.3 pixels and are often reported in hundredths of a pixel. It appears to me that as the centroid of the guide star drifts, even a fraction of the distance covered by a single pixel, it's movement is detected and corrected for. Since my guide and imaging chips are using the same optics, it seems reasonable to me that centroids of stars on the imaging chip would also not be varying by more than these amounts. This is what I meant by subpixel variation on the imaging chip. Centroids are not moving a distance greater than the span of a pixel during the integration.

                          The bottom line is that if you're not imaging at long focal lengths, you probably don't need to guide at long focal lengths either. This was the point I was trying to make in response to the original post in this thread. I hope I've done a better job here.

                          As to film vs CCD, Ron has given a better explanation than I could. In addition to his comments I suspect that the higher sensitivity and linearity of response of the CCD also help to make it more demanding than film, especially as exposure time increases. Of course, I don't mind being corrected if I'm wrong about this.


                          Brady
                          http://members.home.net/bradydjohnson/widefield.htm





                          ----- Original Message -----
                          From: _kevin1231@...
                          To: ccd-newastro@yahoogroups.com
                          Sent: Saturday, October 27, 2001 12:38 PM
                          Subject: [ccd-newastro] Re: imaging/guiding question from a new member


                          --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...> wrote:
                          >
                          > With CCDs you can achieve subpixel resolution while autoguiding. If
                          your guider and imager are operating at the same focal length, then
                          you would also get subpixel *variation* on your imaging chip. More
                          specifically, a point source on your imaging chip would never leave
                          the boundaries of a single pixel (assuming your mount/guider operate
                          properly). On film, variation in the position of a point source over
                          an area the size of a CCD pixel could well ruin the image. With the
                          CCD, you wouldn't even know there had been variation in the pointing,
                          since all light was confined to the pixel.
                          >

                          Brady,

                          I was hoping you could explain above a bit more as I don't
                          understand. I thought film was more forgiving than CCD. I have
                          heard many people claim a particular mount is good astrophotography
                          platform, but not good enough for CCD which "demands more". If your
                          guiding at f10 with modest size pixels you would get drift of less
                          than a pixel, which would cover a couple arcseconds. This would show
                          up on film, but not another ccd? In theory I guess this makes sense
                          in that film should have finer resolution than ccd. Does this
                          support my thinking that a film based image can actually show much
                          more detail than CCD? Though most Great CCD images I see (high
                          resolution galactic type) by Ron, robert adam ect, blow away most
                          anything I have seen on film. But I still give the widefield not to
                          film as the images are just so much more pleasing.

                          Kevin


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                          [Non-text portions of this message have been removed]
                        • Ron Wodaski
                          One thing to be aware of is that the pixel size on the guide chip is significantly larger than the pixel size on the imaging chip. The imaging chip has
                          Message 12 of 23 , Oct 27, 2001
                          • 0 Attachment
                            One thing to be aware of is that the pixel size on the guide chip is
                            significantly larger than the pixel size on the imaging chip. The imaging
                            chip has 9-micron pixels, while the guide chip has non-square pixels that
                            average out around 15 microns. So a half-pixel error on the guide chip is
                            almost a full pixel on the imaging chip. So for accurate comparisons, you
                            would need to convert the pixels on both chips into arcseconds of sky
                            coverage (image scale).

                            Because the star images are spread out across pixels, the main goal is to
                            keep the guide corrections smaller than about half the diameter of your dim
                            stars. So if your dim stars are occupying 3 pixels on the imaging chip, say,
                            then you want to guide to 1.5 * 9 microns, or about 13 micron accuracy.
                            That's just a little below one pixel on the guide chip, so if you errors are
                            within about 1 pixel (+/- 0.5 pixel) on the guide chip, you will get decent
                            results on the imaging chip.

                            Ron Wodaski
                            The New CCD Astronomy
                            http://www.newastro.com

                            -----Original Message-----
                            From: Brady Johnson [mailto:bradydjohnson@...]
                            Sent: Saturday, October 27, 2001 11:46 AM
                            To: ccd-newastro@yahoogroups.com
                            Subject: Re: [ccd-newastro] Re: imaging/guiding question from a new
                            member


                            Hi Kevin:

                            I see Ron has posted a nice response to this. I'd like to add a couple of
                            thoughts too.

                            First, I should give you some background. I am a novice at imaging. Most of
                            my imaging so far is being done with 9 micron pixels using 50 - 200mm camera
                            lenses attached to an ST8/CFW8. I often selfguide my exposures, so the guide
                            chip (which has slightly larger pixels) is using the same optics.

                            The corrections I see during the self guide sessions rarely exceed 0.3
                            pixels and are often reported in hundredths of a pixel. It appears to me
                            that as the centroid of the guide star drifts, even a fraction of the
                            distance covered by a single pixel, it's movement is detected and corrected
                            for. Since my guide and imaging chips are using the same optics, it seems
                            reasonable to me that centroids of stars on the imaging chip would also not
                            be varying by more than these amounts. This is what I meant by subpixel
                            variation on the imaging chip. Centroids are not moving a distance greater
                            than the span of a pixel during the integration.

                            The bottom line is that if you're not imaging at long focal lengths, you
                            probably don't need to guide at long focal lengths either. This was the
                            point I was trying to make in response to the original post in this thread.
                            I hope I've done a better job here.

                            As to film vs CCD, Ron has given a better explanation than I could. In
                            addition to his comments I suspect that the higher sensitivity and linearity
                            of response of the CCD also help to make it more demanding than film,
                            especially as exposure time increases. Of course, I don't mind being
                            corrected if I'm wrong about this.


                            Brady
                            http://members.home.net/bradydjohnson/widefield.htm





                            ----- Original Message -----
                            From: _kevin1231@...
                            To: ccd-newastro@yahoogroups.com
                            Sent: Saturday, October 27, 2001 12:38 PM
                            Subject: [ccd-newastro] Re: imaging/guiding question from a new member


                            --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...> wrote:
                            >
                            > With CCDs you can achieve subpixel resolution while autoguiding. If
                            your guider and imager are operating at the same focal length, then
                            you would also get subpixel *variation* on your imaging chip. More
                            specifically, a point source on your imaging chip would never leave
                            the boundaries of a single pixel (assuming your mount/guider operate
                            properly). On film, variation in the position of a point source over
                            an area the size of a CCD pixel could well ruin the image. With the
                            CCD, you wouldn't even know there had been variation in the pointing,
                            since all light was confined to the pixel.
                            >

                            Brady,

                            I was hoping you could explain above a bit more as I don't
                            understand. I thought film was more forgiving than CCD. I have
                            heard many people claim a particular mount is good astrophotography
                            platform, but not good enough for CCD which "demands more". If your
                            guiding at f10 with modest size pixels you would get drift of less
                            than a pixel, which would cover a couple arcseconds. This would show
                            up on film, but not another ccd? In theory I guess this makes sense
                            in that film should have finer resolution than ccd. Does this
                            support my thinking that a film based image can actually show much
                            more detail than CCD? Though most Great CCD images I see (high
                            resolution galactic type) by Ron, robert adam ect, blow away most
                            anything I have seen on film. But I still give the widefield not to
                            film as the images are just so much more pleasing.

                            Kevin


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                          • _kevin1231@excite.com
                            I don t either but wanted your clarification. He had me second guessing what I have observed but not an expert in. It seemed to me that the most detailed
                            Message 13 of 23 , Oct 27, 2001
                            • 0 Attachment
                              I don't either but wanted your clarification. He had me second
                              guessing what I have observed but not an expert in. It seemed to me
                              that the most detailed images of galaxies have been with CCD.

                              So subpixel guiding should be more than adequate for film images.
                              That fits with my experience as well. As I mentioned, I have done
                              unguided images at F10 on film, for up to 3 minutes with bullets for
                              stars. when down around 1.0"/pixel, I am lucky to get 15 seconds
                              before stars are noticably egg shaped.

                              Kevin

                              --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                              > Actually, I don't agree with what Brady said. I was trying to state
                              a
                              > different case in my earlier message. As far as I know, most CCD
                              cameras are
                              > going to provide higher resolution and a smaller FOV than film.
                              >
                              > Ron Wodaski
                              > The New CCD Astronomy
                              > http://www.newastro.com
                              >
                              > -----Original Message-----
                              > From: _kevin1231@e... [mailto:_kevin1231@e...]
                              > Sent: Saturday, October 27, 2001 11:37 AM
                              > To: ccd-newastro@y...
                              > Subject: [ccd-newastro] Re: imaging/guiding question from a new
                              member
                              >
                              >
                              > Ron,
                              > Thanks for the reply. I unfortunately am back to not understanding
                              > Bradys comments. Are they accurate? I would think sub pixel
                              guiding
                              > would be far more than enough for a film image. I have taken what
                              > seem to be sharp images (albeit short) unguided at F10 for several
                              > minutes. Much, much longer than the sometimes 15 seconds I can get
                              > when imaging at .5" per pixel.
                              >
                              > I am also familiar with beauty of sub pixel guiding. Tried out an
                              > STV and could not believe I can guide with a camera lens while
                              > imaging on CCD.
                              >
                              > Can you rephrase his comments if correct, so that I can understand
                              > what he means?
                              >
                              > Thanks,
                              > Kevin
                              >
                              >
                              > --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                              > > Historically, the "pixel size" of film has been considered to be
                              > around 25
                              > > microns. That's substantially larger than many of today's cameras.
                              > So, in
                              > > general, it is reasonable to assume that CCD is higher resolution
                              > that film,
                              > > and therefore more demanding.
                              > >
                              > > Strictly speaking, of course, film has a grain size, not a pixel
                              > size, but
                              > > other than the non-orthogonality of the grains, this turns out to
                              > be useful
                              > > anyway.
                              > >
                              > > There are some films that have a higher resolution than this. For
                              > example,
                              > > hypered Tech Pan has about as high a film resolution as you are
                              > going to
                              > > find, yet I can duplicate with a 4" 9-micron CCD the same
                              > resolution you can
                              > > get with a much larger instrument using Tech Pan. Have never
                              worked
                              > out the
                              > > numbers, but my conclusion is that CCD pixels are much smaller
                              than
                              > film
                              > > grains.
                              > >
                              > > It's also worth addressing what "sub pixel guiding" really means.
                              > With an
                              > > STV, the math is sophisticated enough to centroid a star down to
                              > about
                              > > 1/30th of a pixel. This means that you can guide down to 0.2
                              > arcseconds with
                              > > only a 500mm guidescope. So there is really no need to use a
                              longer
                              > > guidescope with the STV. At 500mm, you can ensure the accuracy and
                              > > flexibility of guiding by using a fast (f/4, f/5, f/6) guidescope.
                              > >
                              > > It is a mistake to think of stars "covering a pixel" or staying
                              > within the
                              > > domain of a pixel. Atmospheric turbulence almost always smears the
                              > image.
                              > > Even Adam Block's recent images from Kitt Peak, which are taken at
                              > f/10 on a
                              > > 16" LX200 with the 9-micron pixels of an ST-8, for 0.438
                              arcseconds
                              > per
                              > > pixel image scale, clearly show mag 20 stars covering many pixels.
                              > At the
                              > > other extreme, a 50mm lens and an ST-8E, at about 40 arcseconds
                              per
                              > pixel,
                              > > still show round stars covering multiple pixels.
                              > >
                              > > I have found that it is best to verify theories with some
                              practical
                              > testing.
                              > > The actual physics of CCD imaging has shaken many a working
                              > hypothesis. <G>
                              > >
                              > > Ron Wodaski
                              > > The New CCD Astronomy
                              > > http://www.newastro.com
                              > >
                              > > -----Original Message-----
                              > > From: _kevin1231@e... [mailto:_kevin1231@e...]
                              > > Sent: Saturday, October 27, 2001 9:39 AM
                              > > To: ccd-newastro@y...
                              > > Subject: [ccd-newastro] Re: imaging/guiding question from a new
                              > member
                              > >
                              > >
                              > > --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...>
                              > wrote:
                              > > >
                              > > > With CCDs you can achieve subpixel resolution while autoguiding.
                              > If
                              > > your guider and imager are operating at the same focal length,
                              then
                              > > you would also get subpixel *variation* on your imaging chip. More
                              > > specifically, a point source on your imaging chip would never
                              leave
                              > > the boundaries of a single pixel (assuming your mount/guider
                              operate
                              > > properly). On film, variation in the position of a point source
                              over
                              > > an area the size of a CCD pixel could well ruin the image. With
                              the
                              > > CCD, you wouldn't even know there had been variation in the
                              > pointing,
                              > > since all light was confined to the pixel.
                              > > >
                              > >
                              > > Brady,
                              > >
                              > > I was hoping you could explain above a bit more as I don't
                              > > understand. I thought film was more forgiving than CCD. I have
                              > > heard many people claim a particular mount is good
                              astrophotography
                              > > platform, but not good enough for CCD which "demands more". If
                              your
                              > > guiding at f10 with modest size pixels you would get drift of less
                              > > than a pixel, which would cover a couple arcseconds. This would
                              > show
                              > > up on film, but not another ccd? In theory I guess this makes
                              sense
                              > > in that film should have finer resolution than ccd. Does this
                              > > support my thinking that a film based image can actually show much
                              > > more detail than CCD? Though most Great CCD images I see (high
                              > > resolution galactic type) by Ron, robert adam ect, blow away most
                              > > anything I have seen on film. But I still give the widefield not
                              to
                              > > film as the images are just so much more pleasing.
                              > >
                              > > Kevin
                              > >
                              > >
                              > >
                              > > To unsubscribe from this group, send an email to:
                              > > ccd-newastro-unsubscribe@egroups.com
                              > >
                              > >
                              > >
                              > > Your use of Yahoo! Groups is subject to
                              > http://docs.yahoo.com/info/terms/
                              >
                              >
                              >
                              > To unsubscribe from this group, send an email to:
                              > ccd-newastro-unsubscribe@egroups.com
                              >
                              >
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                            • _kevin1231@excite.com
                              Thanks Brady for the clarification. I thought you said that drift of
                              Message 14 of 23 , Oct 27, 2001
                              • 0 Attachment
                                Thanks Brady for the clarification. I thought you said that drift of
                                <1 pixel at long focal length would noticably trail stars on a film
                                based image which did not seem to make sense to me.

                                Kevin

                                --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...> wrote:
                                > Hi Kevin:
                                >
                                > I see Ron has posted a nice response to this. I'd like to add a
                                couple of thoughts too.
                                >
                                > First, I should give you some background. I am a novice at imaging.
                                Most of my imaging so far is being done with 9 micron pixels using
                                50 - 200mm camera lenses attached to an ST8/CFW8. I often selfguide
                                my exposures, so the guide chip (which has slightly larger pixels) is
                                using the same optics.
                                >
                                > The corrections I see during the self guide sessions rarely exceed
                                0.3 pixels and are often reported in hundredths of a pixel. It
                                appears to me that as the centroid of the guide star drifts, even a
                                fraction of the distance covered by a single pixel, it's movement is
                                detected and corrected for. Since my guide and imaging chips are
                                using the same optics, it seems reasonable to me that centroids of
                                stars on the imaging chip would also not be varying by more than
                                these amounts. This is what I meant by subpixel variation on the
                                imaging chip. Centroids are not moving a distance greater than the
                                span of a pixel during the integration.
                                >
                                > The bottom line is that if you're not imaging at long focal
                                lengths, you probably don't need to guide at long focal lengths
                                either. This was the point I was trying to make in response to the
                                original post in this thread. I hope I've done a better job here.
                                >
                                > As to film vs CCD, Ron has given a better explanation than I could.
                                In addition to his comments I suspect that the higher sensitivity and
                                linearity of response of the CCD also help to make it more demanding
                                than film, especially as exposure time increases. Of course, I don't
                                mind being corrected if I'm wrong about this.
                                >
                                >
                                > Brady
                                > http://members.home.net/bradydjohnson/widefield.htm
                                >
                                >
                                >
                                >
                                >
                                > ----- Original Message -----
                                > From: _kevin1231@e...
                                > To: ccd-newastro@y...
                                > Sent: Saturday, October 27, 2001 12:38 PM
                                > Subject: [ccd-newastro] Re: imaging/guiding question from a new
                                member
                                >
                                >
                                > --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...>
                                wrote:
                                > >
                                > > With CCDs you can achieve subpixel resolution while
                                autoguiding. If
                                > your guider and imager are operating at the same focal length,
                                then
                                > you would also get subpixel *variation* on your imaging chip.
                                More
                                > specifically, a point source on your imaging chip would never
                                leave
                                > the boundaries of a single pixel (assuming your mount/guider
                                operate
                                > properly). On film, variation in the position of a point source
                                over
                                > an area the size of a CCD pixel could well ruin the image. With
                                the
                                > CCD, you wouldn't even know there had been variation in the
                                pointing,
                                > since all light was confined to the pixel.
                                > >
                                >
                                > Brady,
                                >
                                > I was hoping you could explain above a bit more as I don't
                                > understand. I thought film was more forgiving than CCD. I have
                                > heard many people claim a particular mount is good
                                astrophotography
                                > platform, but not good enough for CCD which "demands more". If
                                your
                                > guiding at f10 with modest size pixels you would get drift of
                                less
                                > than a pixel, which would cover a couple arcseconds. This would
                                show
                                > up on film, but not another ccd? In theory I guess this makes
                                sense
                                > in that film should have finer resolution than ccd. Does this
                                > support my thinking that a film based image can actually show
                                much
                                > more detail than CCD? Though most Great CCD images I see (high
                                > resolution galactic type) by Ron, robert adam ect, blow away most
                                > anything I have seen on film. But I still give the widefield not
                                to
                                > film as the images are just so much more pleasing.
                                >
                                > Kevin
                                >
                                >
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                                > ADVERTISEMENT
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                                > [Non-text portions of this message have been removed]
                              • ben@stanfordalumni.org
                                My opinion - the best film shots (with fine-grained Tech Pan) and the best CCD shots are approximately equal in grain, with an edge going to CCD (and the
                                Message 15 of 23 , Oct 29, 2001
                                • 0 Attachment
                                  My opinion - the best film shots (with fine-grained Tech Pan) and the
                                  best CCD shots are approximately equal in grain, with an edge going
                                  to CCD (and the latter is getting better all the time; I don't see
                                  nearly as much progress on the film front).

                                  Here's some more technical info that seems to indicate the same:

                                  This interesting article

                                  http://digilander.iol.it/comolli/resol2.htm

                                  opines that Tech Pan's grain is about 3 microns. The article
                                  indicates that "the smallest star sizes that can be achieved with
                                  this film are about 9-10 microns". Some of the top amateurs are
                                  producing images of 1.5" FWHM, so at (for example) 80" focal length
                                  with 6.8 micron pixels they're getting minimum star sizes of about 13
                                  microns (if I didn't screw that up). So they're about equivalent on
                                  that front - a film "grain" seems to vary so much that I think this
                                  is a pretty good metric.

                                  Berry & Burnell's "The Handbook of Astronomical Image Processing"
                                  says that "Although individual grains are only a few microns across,
                                  the smallest effective area capable of producing a good signal-to-
                                  noise ratio ranges from 5 to 20 microns. [...] a single frame of fine-
                                  grain 35-mm film offers the resolutions of a 10 megapixel electronic
                                  detector". This translates into 9.35 micron square pixels, and the
                                  astronomical CCD's with which I'm familiar are between 6.8 and 24
                                  microns.

                                  So overall, I'd agree with Ron that a CCD has a finer effective grain
                                  than the best film, given the uniform density of a CCD, the lack of
                                  reciprocity failure, variable grain sizes, etc.
                                  b

                                  --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                                  > Historically, the "pixel size" of film has been considered to be
                                  around 25
                                  > microns. That's substantially larger than many of today's cameras.
                                  So, in
                                  > general, it is reasonable to assume that CCD is higher resolution
                                  that film,
                                  > and therefore more demanding.
                                  >
                                  > Strictly speaking, of course, film has a grain size, not a pixel
                                  size, but
                                  > other than the non-orthogonality of the grains, this turns out to
                                  be useful
                                  > anyway.
                                  >
                                  > There are some films that have a higher resolution than this. For
                                  example,
                                  > hypered Tech Pan has about as high a film resolution as you are
                                  going to
                                  > find, yet I can duplicate with a 4" 9-micron CCD the same
                                  resolution you can
                                  > get with a much larger instrument using Tech Pan. Have never worked
                                  out the
                                  > numbers, but my conclusion is that CCD pixels are much smaller than
                                  film
                                  > grains.
                                  >
                                  > It's also worth addressing what "sub pixel guiding" really means.
                                  With an
                                  > STV, the math is sophisticated enough to centroid a star down to
                                  about
                                  > 1/30th of a pixel. This means that you can guide down to 0.2
                                  arcseconds with
                                  > only a 500mm guidescope. So there is really no need to use a longer
                                  > guidescope with the STV. At 500mm, you can ensure the accuracy and
                                  > flexibility of guiding by using a fast (f/4, f/5, f/6) guidescope.
                                  >
                                  > It is a mistake to think of stars "covering a pixel" or staying
                                  within the
                                  > domain of a pixel. Atmospheric turbulence almost always smears the
                                  image.
                                  > Even Adam Block's recent images from Kitt Peak, which are taken at
                                  f/10 on a
                                  > 16" LX200 with the 9-micron pixels of an ST-8, for 0.438 arcseconds
                                  per
                                  > pixel image scale, clearly show mag 20 stars covering many pixels.
                                  At the
                                  > other extreme, a 50mm lens and an ST-8E, at about 40 arcseconds per
                                  pixel,
                                  > still show round stars covering multiple pixels.
                                  >
                                  > I have found that it is best to verify theories with some practical
                                  testing.
                                  > The actual physics of CCD imaging has shaken many a working
                                  hypothesis. <G>
                                  >
                                  > Ron Wodaski
                                  > The New CCD Astronomy
                                  > http://www.newastro.com
                                  >
                                  > -----Original Message-----
                                  > From: _kevin1231@e... [mailto:_kevin1231@e...]
                                  > Sent: Saturday, October 27, 2001 9:39 AM
                                  > To: ccd-newastro@y...
                                  > Subject: [ccd-newastro] Re: imaging/guiding question from a new
                                  member
                                  >
                                  >
                                  > --- In ccd-newastro@y..., "Brady Johnson" <bradydjohnson@h...>
                                  wrote:
                                  > >
                                  > > With CCDs you can achieve subpixel resolution while autoguiding.
                                  If
                                  > your guider and imager are operating at the same focal length, then
                                  > you would also get subpixel *variation* on your imaging chip. More
                                  > specifically, a point source on your imaging chip would never leave
                                  > the boundaries of a single pixel (assuming your mount/guider operate
                                  > properly). On film, variation in the position of a point source over
                                  > an area the size of a CCD pixel could well ruin the image. With the
                                  > CCD, you wouldn't even know there had been variation in the
                                  pointing,
                                  > since all light was confined to the pixel.
                                  > >
                                  >
                                  > Brady,
                                  >
                                  > I was hoping you could explain above a bit more as I don't
                                  > understand. I thought film was more forgiving than CCD. I have
                                  > heard many people claim a particular mount is good astrophotography
                                  > platform, but not good enough for CCD which "demands more". If your
                                  > guiding at f10 with modest size pixels you would get drift of less
                                  > than a pixel, which would cover a couple arcseconds. This would
                                  show
                                  > up on film, but not another ccd? In theory I guess this makes sense
                                  > in that film should have finer resolution than ccd. Does this
                                  > support my thinking that a film based image can actually show much
                                  > more detail than CCD? Though most Great CCD images I see (high
                                  > resolution galactic type) by Ron, robert adam ect, blow away most
                                  > anything I have seen on film. But I still give the widefield not to
                                  > film as the images are just so much more pleasing.
                                  >
                                  > Kevin
                                  >
                                  >
                                  >
                                  > To unsubscribe from this group, send an email to:
                                  > ccd-newastro-unsubscribe@egroups.com
                                  >
                                  >
                                  >
                                  > Your use of Yahoo! Groups is subject to
                                  http://docs.yahoo.com/info/terms/
                                • Ron Wodaski
                                  If you would like to contribute a short comment about the book, to be included in a what readers are saying section on the back cover and/or inside the front
                                  Message 16 of 23 , Oct 29, 2001
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                                    If you would like to contribute a short comment about the book, to be
                                    included in a "what readers are saying" section on the back cover and/or
                                    inside the front cover, please either post it here or send it to me in
                                    private email. These are intended to help prospective readers get a feel for
                                    why the book would be valuable to them.

                                    By supplying a quote, you agree to allow me to use it in/on the book, and to
                                    use your name as the source of the quote. I need these in the next two days
                                    (deadline is Wednesday noon, EST).

                                    Thanks!

                                    Ron Wodaski
                                    The New CCD Astronomy
                                    http://www.newastro.com
                                  • Ron Wodaski
                                    I have had some requests for a T-shirt for book readers, and I d like to come up with something nice. I would like a volunteer graphic artist to come up with
                                    Message 17 of 23 , Oct 29, 2001
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                                      I have had some requests for a T-shirt for book readers, and I'd like to
                                      come up with something nice. I would like a volunteer graphic artist to come
                                      up with something. One idea has been submitted already: a night-owl concept,
                                      but with CCD chips for eyes. <g> I'd like someone to either take this idea
                                      and run with it, or come up with some better ideas.

                                      If you have a graphics background, and have some ideas on how to make this
                                      happen, I'll take your finished design and get the shirts made up.

                                      Please respond to me by private email. However, if anyone has suggestions
                                      for a good shirt, you can either post them here or send me email. Perhaps if
                                      we get some ideas tossed around in this group we can reach a consensus on
                                      ideas to hand over to the graphics person, who will have final say!

                                      Ron Wodaski
                                      The New CCD Astronomy
                                      http://www.newastro.com
                                    • Ron Wodaski
                                      Here is a link to the current cover design: http://www.newastro.com/newastro/images/cover_art_new.jpg Ron Wodaski The New CCD Astronomy http://www.newastro.com
                                      Message 18 of 23 , Oct 29, 2001
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                                        Here is a link to the current cover design:

                                        http://www.newastro.com/newastro/images/cover_art_new.jpg

                                        Ron Wodaski
                                        The New CCD Astronomy
                                        http://www.newastro.com
                                      • Randy Nulman
                                        Ron..for what it s worth, here s my testimonial: I attempted ccd imaging in the mid 1990 s and gave up on it after some pretty dismal results. After learning
                                        Message 19 of 23 , Oct 29, 2001
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                                          Ron..for what it's worth, here's my testimonial:

                                          I attempted ccd imaging in the mid 1990's and gave up on it after
                                          some pretty dismal results. After learning about this book, and
                                          utilizing the information provided here, I took up the hobby again
                                          and was producing good images after just a few nights out (and
                                          excellent images after just a few months!)

                                          HTH,

                                          Randy Nulman

                                          --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                                          > If you would like to contribute a short comment about the book, to
                                          be
                                          > included in a "what readers are saying" section on the back cover
                                          and/or
                                          > inside the front cover, please either post it here or send it to me
                                          in
                                          > private email. These are intended to help prospective readers get a
                                          feel for
                                          > why the book would be valuable to them.
                                          >
                                          > By supplying a quote, you agree to allow me to use it in/on the
                                          book, and to
                                          > use your name as the source of the quote. I need these in the next
                                          two days
                                          > (deadline is Wednesday noon, EST).
                                          >
                                          > Thanks!
                                          >
                                          > Ron Wodaski
                                          > The New CCD Astronomy
                                          > http://www.newastro.com
                                        • Ron Wodaski
                                          Thanks. That s a good one for inside the front cover, where I am putting longer, more detailed quotes. Ron Wodaski The New CCD Astronomy
                                          Message 20 of 23 , Oct 29, 2001
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                                            Thanks. That's a good one for inside the front cover, where I am putting
                                            longer, more detailed quotes.

                                            Ron Wodaski
                                            The New CCD Astronomy
                                            http://www.newastro.com

                                            -----Original Message-----
                                            From: Randy Nulman [mailto:rjnulman@...]
                                            Sent: Monday, October 29, 2001 2:44 PM
                                            To: ccd-newastro@yahoogroups.com
                                            Subject: [ccd-newastro] Re: Cover quotes for the book needed


                                            Ron..for what it's worth, here's my testimonial:

                                            I attempted ccd imaging in the mid 1990's and gave up on it after
                                            some pretty dismal results. After learning about this book, and
                                            utilizing the information provided here, I took up the hobby again
                                            and was producing good images after just a few nights out (and
                                            excellent images after just a few months!)

                                            HTH,

                                            Randy Nulman

                                            --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                                            > If you would like to contribute a short comment about the book, to
                                            be
                                            > included in a "what readers are saying" section on the back cover
                                            and/or
                                            > inside the front cover, please either post it here or send it to me
                                            in
                                            > private email. These are intended to help prospective readers get a
                                            feel for
                                            > why the book would be valuable to them.
                                            >
                                            > By supplying a quote, you agree to allow me to use it in/on the
                                            book, and to
                                            > use your name as the source of the quote. I need these in the next
                                            two days
                                            > (deadline is Wednesday noon, EST).
                                            >
                                            > Thanks!
                                            >
                                            > Ron Wodaski
                                            > The New CCD Astronomy
                                            > http://www.newastro.com



                                            To unsubscribe from this group, send an email to:
                                            ccd-newastro-unsubscribe@egroups.com



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                                          • F W Hainley
                                            Ron, Please use this if you like: As a newcomer to CCD imaging, I was reading everything I could find. I ordered Ron s book before shutting down my computer
                                            Message 21 of 23 , Oct 29, 2001
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                                              Ron,

                                              Please use this if you like:

                                              As a newcomer to CCD imaging, I was reading everything I could find. I
                                              ordered Ron's book before shutting down my computer after reading the
                                              first online drafts. I eagerly await delivery of my copy of book.

                                              Frank Hainley
                                              Moraga, California

                                              Ron Wodaski wrote:

                                              > If you would like to contribute a short comment about the book, to be
                                              > included in a "what readers are saying" section on the back cover
                                              > and/or
                                              > inside the front cover, please either post it here or send it to me in
                                              >
                                              > private email. These are intended to help prospective readers get a
                                              > feel for
                                              > why the book would be valuable to them.
                                              >
                                              > By supplying a quote, you agree to allow me to use it in/on the book,
                                              > and to
                                              > use your name as the source of the quote. I need these in the next two
                                              > days
                                              > (deadline is Wednesday noon, EST).
                                              >
                                              > Thanks!
                                              >
                                              > Ron Wodaski
                                              > The New CCD Astronomy
                                              > http://www.newastro.com
                                              >
                                              >
                                              >
                                              > Yahoo! Groups Sponsor
                                              ADVERTISEMENT


                                              >
                                              > To unsubscribe from this group, send an email to:
                                              > ccd-newastro-unsubscribe@egroups.com
                                              >
                                              >
                                              >
                                              > Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.


                                              [Non-text portions of this message have been removed]
                                            • markh@speakeasy.org
                                              Ron, Here are two as my shots: When I pack for the dark sky site, The New Astronomy gets packed first... Even before my scope! A scope, a CCD camera, a little
                                              Message 22 of 23 , Oct 29, 2001
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                                                Ron,

                                                Here are two as my shots:

                                                When I pack for the dark sky site, The New Astronomy gets packed
                                                first... Even before my scope!

                                                A scope, a CCD camera, a little starlight, and The New Astronomy are
                                                a recipe for success! Your images will improve dramatically almost
                                                overnight!

                                                Mark R. Holbrook
                                                http://www.ccdastronomy.com

                                                --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
                                                > If you would like to contribute a short comment about the book, to
                                                be
                                                > included in a "what readers are saying" section on the back cover
                                                and/or
                                                > inside the front cover, please either post it here or send it to me
                                                in
                                                > private email. These are intended to help prospective readers get a
                                                feel for
                                                > why the book would be valuable to them.
                                                >
                                                > By supplying a quote, you agree to allow me to use it in/on the
                                                book, and to
                                                > use your name as the source of the quote. I need these in the next
                                                two days
                                                > (deadline is Wednesday noon, EST).
                                                >
                                                > Thanks!
                                                >
                                                > Ron Wodaski
                                                > The New CCD Astronomy
                                                > http://www.newastro.com
                                              • rander3127@aol.com
                                                Ron Wodaski Subject: Cover quotes for the book needed If you would like to contribute a short comment about the book, to be included in a
                                                Message 23 of 23 , Oct 31, 2001
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                                                  Ron Wodaski" <ronw@...>
                                                  Subject: Cover quotes for the book needed

                                                  If you would like to contribute a short comment about the book, to be
                                                  included in a "what readers are saying" section on the back cover and/or
                                                  inside the front cover, please either post it here or send it to me in
                                                  private email.

                                                  "The ABC's of CCD's are presented in a lucid and
                                                  entertaining fashion; An excellent resource."

                                                  or:

                                                  Emulsion photography: "Driven to extinction, back
                                                  for revenge." :)
                                                  -Rich
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