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Exposure Duration

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  • mandellgl
    Friends: I am using a SXVF-M8C camera in a moderately light-polluted suburban sky with a Hutech LPS filter. I was trying to get an idea how long to expose
    Message 1 of 16 , Apr 30, 2007
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      Friends:

      I am using a SXVF-M8C camera in a moderately light-polluted suburban
      sky with a Hutech LPS filter.

      I was trying to get an idea how long to expose subframes using a
      calculator found on the Starizona website:

      http://starizona.com/acb/ccd/calc_ideal.aspx

      Based upon the Sky ADU measured with a 3 minute exposure (approximately
      2000) and 5% contribution from readout noise, the calculated
      subexposure duration is 4 minutes. That seems kind of short. I was
      used to shooting 10-12 minute exposures at the same site using a Canon
      EOS 350D camera.

      What is the problem shooting longer subframes than calculated? Is
      there another way to estimate subframe duration?

      Gordon Mandell
    • jmize@svic.net
      Gordon, go to CCDware s Resources page for their Exposure Calculator, and other tools, http://www.ccdware.com/resources/subexposure.cfm You ll probably find
      Message 2 of 16 , May 1, 2007
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        Gordon, go to CCDware's Resources page for their Exposure Calculator, and other tools,
        http://www.ccdware.com/resources/subexposure.cfm You'll probably find the results you'll get here will be similar to the ones
        you already gotten using Starzonia's calculator.

        You're now using a CCD Camera specifically designed fot astrophotography, not a DSLR 'modified' for taking pictures of the
        stars. The dedicated SVX CCD Camera is much more sensitive and will acquire data much more efficiently. Don't get me wrong,
        I've seen some outstanding DSLR images such as the old warhorse film imager and APML'er, Chuck Vaughn whoes images are at
        http://www.ccdware.com/resources/subexposure.cfm

        Being used to exposing film upwards of 90mins I also wanted to expose long. The CCD chip specifically designed for imagery is so
        sensitive that the image will be over exposed easily. Have you ever seen images where "all" the stars were pure white? You're
        in a diffenernt sensitivity world now.

        If you look into the Archives of this group you'll find several threads discussing exposure durations, short vs long, which
        thoroughly discuss all the reasons for one direction or the other. In the long run it's up to you whether you shoot long or
        short sub frames...joe :)


        ------- Original Message -------
        From : mandellgl[mailto:gmandell@...]
        Sent : 5/1/2007 1:37:25 AM
        To : ccd-newastro@yahoogroups.com
        Cc :
        Subject : RE: [ccd-newastro] Exposure Duration

        Friends:

        I am using a SXVF-M8C camera in a moderately light-polluted suburban
        sky with a Hutech LPS filter.

        I was trying to get an idea how long to expose subframes using a
        calculator found on the Starizona website:

        http://starizona.com/acb/ccd/calc_ideal.aspx

        Based upon the Sky ADU measured with a 3 minute exposure (approximately
        2000) and 5% contribution from readout noise, the calculated
        subexposure duration is 4 minutes. That seems kind of short. I was
        used to shooting 10-12 minute exposures at the same site using a Canon
        EOS 350D camera.

        What is the problem shooting longer subframes than calculated? Is
        there another way to estimate subframe duration?

        Gordon Mandell



        Yahoo! Groups Links
      • Neil Fleming
        My only question would be is this supposed to be a pre-calibration or post-calibration background statistic? ... www.flemingastrophotography.com Direct from
        Message 3 of 16 , May 1, 2007
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          My only question would be is this supposed to be a
          pre-calibration or post-calibration background
          statistic?

          ...Neil

          --- mandellgl <gmandell@...> wrote:

          > Friends:
          >
          > I am using a SXVF-M8C camera in a moderately
          > light-polluted suburban
          > sky with a Hutech LPS filter.
          >
          > I was trying to get an idea how long to expose
          > subframes using a
          > calculator found on the Starizona website:
          >
          > http://starizona.com/acb/ccd/calc_ideal.aspx
          >
          > Based upon the Sky ADU measured with a 3 minute
          > exposure (approximately
          > 2000) and 5% contribution from readout noise, the
          > calculated
          > subexposure duration is 4 minutes. That seems kind
          > of short. I was
          > used to shooting 10-12 minute exposures at the same
          > site using a Canon
          > EOS 350D camera.
          >
          > What is the problem shooting longer subframes than
          > calculated? Is
          > there another way to estimate subframe duration?
          >
          > Gordon Mandell
          >
          >


          www.flemingastrophotography.com
          Direct from Boston - brilliant diamonds in pea soup
        • jmize@svic.net
          Ooops! Chuck s URL didn t make it. If you are interested in some very fine 20Da DSLR images check out his site...joe :) http://astrophotography.aa6g.org/
          Message 4 of 16 , May 1, 2007
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            Ooops! Chuck's URL didn't make it. If you are interested in some very fine 20Da DSLR images check out his site...joe :)

            http://astrophotography.aa6g.org/


            ------- Original Message -------
            From : jmize@...[mailto:jmize@...]
            Sent : 5/1/2007 8:59:37 AM
            To : ccd-newastro@yahoogroups.com
            Cc :
            Subject : RE: [ccd-newastro] Exposure Duration


            Gordon, go to CCDware's Resources page for their Exposure Calculator, and other tools,
            http://www.ccdware.com/resources/subexposure.cfm You'll probably find the results you'll get here will be similar to the ones
            you already gotten using Starzonia's calculator.

            You're now using a CCD Camera specifically designed fot astrophotography, not a DSLR 'modified' for taking pictures of the
            stars. The dedicated SVX CCD Camera is much more sensitive and will acquire data much more efficiently. Don't get me wrong,
            I've seen some outstanding DSLR images such as the old warhorse film imager and APML'er, Chuck Vaughn whoes images are at
            http://www.ccdware.com/resources/subexposure.cfm

            Being used to exposing film upwards of 90mins I also wanted to expose long. The CCD chip specifically designed for imagery is so
            sensitive that the image will be over exposed easily. Have you ever seen images where "all" the stars were pure white? You're
            in a diffenernt sensitivity world now.

            If you look into the Archives of this group you'll find several threads discussing exposure durations, short vs long, which
            thoroughly discuss all the reasons for one direction or the other. In the long run it's up to you whether you shoot long or
            short sub frames...joe :)


            ------- Original Message -------
            From : mandellgl[ mailto:gmandell@...]
            Sent : 5/1/2007 1:37:25 AM
            To : ccd-newastro@yahoogroups.com
            Cc :
            Subject : RE: [ccd-newastro] Exposure Duration

            Friends:

            I am using a SXVF-M8C camera in a moderately light-polluted suburban
            sky with a Hutech LPS filter.

            I was trying to get an idea how long to expose subframes using a
            calculator found on the Starizona website:

            http://starizona.com/acb/ccd/calc_ideal.aspx

            Based upon the Sky ADU measured with a 3 minute exposure (approximately
            2000) and 5% contribution from readout noise, the calculated
            subexposure duration is 4 minutes. That seems kind of short. I was
            used to shooting 10-12 minute exposures at the same site using a Canon
            EOS 350D camera.

            What is the problem shooting longer subframes than calculated? Is
            there another way to estimate subframe duration?

            Gordon Mandell



            Yahoo! Groups Links






            Yahoo! Groups Links
          • Rolf
            Is there some reason, why the calculator does not show the standard ST-8 or ST-8E ? Rolf Subject : RE: [ccd-newastro] Exposure Duration Gordon, go to CCDware s
            Message 5 of 16 , May 1, 2007
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              Is there some reason, why the calculator
              does not show the standard ST-8 or ST-8E
              ?

              Rolf




              Subject : RE: [ccd-newastro] Exposure
              Duration

              Gordon, go to CCDware's Resources page
              for their Exposure Calculator, and other
              tools,
              http://www.ccdware.com/resources/subexpo
              sure.cfm
              <http://www.ccdware.com/resources/subexp
              osure.cfm> You'll probably find the
              results you'll get here will be similar
              to the ones you already gotten using
              Starzonia's calculator.
            • mandellgl
              Neil, I was measuring pre-calibrated background ADU. Gordon
              Message 6 of 16 , May 1, 2007
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                Neil,

                I was measuring pre-calibrated background ADU.

                Gordon

                --- In ccd-newastro@yahoogroups.com, Neil Fleming <neilfleming@...>
                wrote:
                >
                > My only question would be is this supposed to be a
                > pre-calibration or post-calibration background
                > statistic?
                >
                > ...Neil
                >
                > --- mandellgl <gmandell@...> wrote:
                >
                > > Friends:
                > >
                > > I am using a SXVF-M8C camera in a moderately
                > > light-polluted suburban
                > > sky with a Hutech LPS filter.
                > >
                > > I was trying to get an idea how long to expose
                > > subframes using a
                > > calculator found on the Starizona website:
                > >
                > > http://starizona.com/acb/ccd/calc_ideal.aspx
                > >
                > > Based upon the Sky ADU measured with a 3 minute
                > > exposure (approximately
                > > 2000) and 5% contribution from readout noise, the
                > > calculated
                > > subexposure duration is 4 minutes. That seems kind
                > > of short. I was
                > > used to shooting 10-12 minute exposures at the same
                > > site using a Canon
                > > EOS 350D camera.
                > >
                > > What is the problem shooting longer subframes than
                > > calculated? Is
                > > there another way to estimate subframe duration?
                > >
                > > Gordon Mandell
                > >
                > >
                >
                >
                > www.flemingastrophotography.com
                > Direct from Boston - brilliant diamonds in pea soup
                >
              • mandellgl
                Joe, The resulting subexposure duration is very close whether I use the Starizona or CCDWare calculator. If the estimated duration is 240 sec and I expose for
                Message 7 of 16 , May 1, 2007
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                  Joe,

                  The resulting subexposure duration is very close whether I use the
                  Starizona or CCDWare calculator.

                  If the estimated duration is 240 sec and I expose for 480 sec, is
                  there a way to tell if I have overexposed the subframe?

                  I am currently using AstroArt 4.0 to measure image statistics.

                  Gordon

                  --- In ccd-newastro@yahoogroups.com, "jmize@..." <jmize@...> wrote:
                  >
                  >
                  > Gordon, go to CCDware's Resources page for their Exposure
                  Calculator, and other tools,
                  > http://www.ccdware.com/resources/subexposure.cfm You'll probably
                  find the results you'll get here will be similar to the ones
                  > you already gotten using Starzonia's calculator.
                  >
                  > You're now using a CCD Camera specifically designed fot
                  astrophotography, not a DSLR 'modified' for taking pictures of the
                  > stars. The dedicated SVX CCD Camera is much more sensitive and
                  will acquire data much more efficiently. Don't get me wrong,
                  > I've seen some outstanding DSLR images such as the old warhorse
                  film imager and APML'er, Chuck Vaughn whoes images are at
                  > http://www.ccdware.com/resources/subexposure.cfm
                  >
                  > Being used to exposing film upwards of 90mins I also wanted to
                  expose long. The CCD chip specifically designed for imagery is so
                  > sensitive that the image will be over exposed easily. Have you
                  ever seen images where "all" the stars were pure white? You're
                  > in a diffenernt sensitivity world now.
                  >
                  > If you look into the Archives of this group you'll find several
                  threads discussing exposure durations, short vs long, which
                  > thoroughly discuss all the reasons for one direction or the
                  other. In the long run it's up to you whether you shoot long or
                  > short sub frames...joe :)
                  >
                  >
                  > ------- Original Message -------
                  > From : mandellgl[mailto:gmandell@...]
                  > Sent : 5/1/2007 1:37:25 AM
                  > To : ccd-newastro@yahoogroups.com
                  > Cc :
                  > Subject : RE: [ccd-newastro] Exposure Duration
                  >
                  > Friends:
                  >
                  > I am using a SXVF-M8C camera in a moderately light-polluted
                  suburban
                  > sky with a Hutech LPS filter.
                  >
                  > I was trying to get an idea how long to expose subframes using a
                  > calculator found on the Starizona website:
                  >
                  > http://starizona.com/acb/ccd/calc_ideal.aspx
                  >
                  > Based upon the Sky ADU measured with a 3 minute exposure
                  (approximately
                  > 2000) and 5% contribution from readout noise, the calculated
                  > subexposure duration is 4 minutes. That seems kind of short. I
                  was
                  > used to shooting 10-12 minute exposures at the same site using a
                  Canon
                  > EOS 350D camera.
                  >
                  > What is the problem shooting longer subframes than calculated? Is
                  > there another way to estimate subframe duration?
                  >
                  > Gordon Mandell
                  >
                  >
                  >
                  > Yahoo! Groups Links
                  >
                • jmize@svic.net
                  Gordon you appear to understand the minimum exposure calculators the way I do, they suggest the minumum exposure to get above shot and camera noise. Your
                  Message 8 of 16 , May 2, 2007
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                    Gordon you appear to understand the 'minimum' exposure calculators the way I do, they suggest the 'minumum' exposure to get above
                    shot and camera noise. Your question was the same as mine when I first went there, find out how 'long' I should expose my
                    images. Not so, these tools are not for that purpose.

                    What I ended up doing was to find a rich object of both stars and nebula to run some tests. I started with my 'minimum'
                    suggested exposure of 6.7mins and took a series of exposures progressivly longer. As the images came in I calibrated them and
                    inspected them.

                    As the exposures got longer I noted there was more fainter nebula, but the brightest portions of the nebula were being burned out
                    and the brightest stars were getting ragged and bloating from being over exposed. Something I learned from film work was just as
                    if something was out of focuse, if something was over exposed there's not much you could do about it.

                    I settled upon two RGB exposure times for my setup, 10 and 15mins. 10mins images for subjects with bright stars and hot nebula
                    and 15mins for objects with few/no bright stars and no hot nebula portions that would over expose. 90% of the time I use 10mins
                    exposures.

                    I know nothing about AstroArt, I used Photoshop checking the intensities of the brightest star/s. You want the centers to 'just'
                    be reaching 255, not the entire star diameter being 255. Zoom in to 6-800x to do this measuring. Keeping just the center at the
                    maximum value I found gave deminsion to the stars and also maintained colors, otherwise over exposed stars will loose their
                    colors or only have little rings of color around their circunfeneces. Determining the correct exposure for stars also addressed
                    the hot regions of nebulas keeping them from being over exposed, or as over exposed as much, allowing more details to be seen
                    which otherwise would be burned out.

                    I tried reversing my testing, measuring the nebula instead of the stars but this gave me weak flat looking stars. Because stars
                    are constant all over the sky and nebula aren't I returned to measuring stars and live with the few portions of hot nebula.

                    Take some time, have a cup of coffee and formulate your plan for your tests, one night should do it. Save your test images to
                    inspect the next day. You should be able to get a good idea that night but detailed inspection the next day without being
                    interrupted by new exposures will confirm what you may have determined the prior night. Have fun...joe :)


                    ------- Original Message -------
                    From : mandellgl[mailto:gmandell@...]
                    Sent : 5/1/2007 7:46:49 PM
                    To : ccd-newastro@yahoogroups.com
                    Cc :
                    Subject : RE: [ccd-newastro] Re: Exposure Duration

                    Joe,

                    The resulting subexposure duration is very close whether I use the
                    Starizona or CCDWare calculator.

                    If the estimated duration is 240 sec and I expose for 480 sec, is
                    there a way to tell if I have overexposed the subframe?

                    I am currently using AstroArt 4.0 to measure image statistics.

                    Gordon

                    --- In ccd-newastro@yahoogroups.com, "jmize@..." <jmize@...> wrote:
                    >
                    >
                    > Gordon, go to CCDware's Resources page for their Exposure
                    Calculator, and other tools,
                    > http://www.ccdware.com/resources/subexposure.cfm You'll probably
                    find the results you'll get here will be similar to the ones
                    > you already gotten using Starzonia's calculator.
                    >
                    > You're now using a CCD Camera specifically designed fot
                    astrophotography, not a DSLR 'modified' for taking pictures of the
                    > stars. The dedicated SVX CCD Camera is much more sensitive and
                    will acquire data much more efficiently. Don't get me wrong,
                    > I've seen some outstanding DSLR images such as the old warhorse
                    film imager and APML'er, Chuck Vaughn whoes images are at
                    > http://www.ccdware.com/resources/subexposure.cfm
                    >
                    > Being used to exposing film upwards of 90mins I also wanted to
                    expose long. The CCD chip specifically designed for imagery is so
                    > sensitive that the image will be over exposed easily. Have you
                    ever seen images where "all" the stars were pure white? You're
                    > in a diffenernt sensitivity world now.
                    >
                    > If you look into the Archives of this group you'll find several
                    threads discussing exposure durations, short vs long, which
                    > thoroughly discuss all the reasons for one direction or the
                    other. In the long run it's up to you whether you shoot long or
                    > short sub frames...joe :)
                    >
                    >
                    > ------- Original Message -------
                    > From : mandellgl[ mailto:gmandell@...]
                    > Sent : 5/1/2007 1:37:25 AM
                    > To : ccd-newastro@yahoogroups.com
                    > Cc :
                    > Subject : RE: [ccd-newastro] Exposure Duration
                    >
                    > Friends:
                    >
                    > I am using a SXVF-M8C camera in a moderately light-polluted
                    suburban
                    > sky with a Hutech LPS filter.
                    >
                    > I was trying to get an idea how long to expose subframes using a
                    > calculator found on the Starizona website:
                    >
                    > http://starizona.com/acb/ccd/calc_ideal.aspx
                    >
                    > Based upon the Sky ADU measured with a 3 minute exposure
                    (approximately
                    > 2000) and 5% contribution from readout noise, the calculated
                    > subexposure duration is 4 minutes. That seems kind of short. I
                    was
                    > used to shooting 10-12 minute exposures at the same site using a
                    Canon
                    > EOS 350D camera.
                    >
                    > What is the problem shooting longer subframes than calculated? Is
                    > there another way to estimate subframe duration?
                    >
                    > Gordon Mandell
                    >
                    >
                    >
                    > Yahoo! Groups Links
                    >




                    Yahoo! Groups Links
                  • Jim Lafferty
                    Joe Are you using an anti blooming camera? Jim Jim Lafferty jrlafferty@mycingular.blackberry.net shogun000@netzero.com ... From: jmize@svic.net
                    Message 9 of 16 , May 2, 2007
                    • 0 Attachment
                      Joe
                      Are you using an anti blooming camera?
                      Jim

                      Jim Lafferty

                      jrlafferty@...
                      shogun000@...

                      -----Original Message-----
                      From: "jmize@..." <jmize@...>
                      Date: Wed, 2 May 2007 09:58:23
                      To:ccd-newastro@yahoogroups.com
                      Subject: RE: [ccd-newastro] Re: Exposure Duration

                      Gordon you appear to understand the 'minimum' exposure calculators the way I do, they suggest the 'minumum' exposure to get above
                      shot and camera noise. Your question was the same as mine when I first went there, find out how 'long' I should expose my
                      images. Not so, these tools are not for that purpose.

                      What I ended up doing was to find a rich object of both stars and nebula to run some tests. I started with my 'minimum'
                      suggested exposure of 6.7mins and took a series of exposures progressivly longer. As the images came in I calibrated them and
                      inspected them.

                      As the exposures got longer I noted there was more fainter nebula, but the brightest portions of the nebula were being burned out
                      and the brightest stars were getting ragged and bloating from being over exposed. Something I learned from film work was just as
                      if something was out of focuse, if something was over exposed there's not much you could do about it.

                      I settled upon two RGB exposure times for my setup, 10 and 15mins. 10mins images for subjects with bright stars and hot nebula
                      and 15mins for objects with few/no bright stars and no hot nebula portions that would over expose. 90% of the time I use 10mins
                      exposures.

                      I know nothing about AstroArt, I used Photoshop checking the intensities of the brightest star/s. You want the centers to 'just'
                      be reaching 255, not the entire star diameter being 255. Zoom in to 6-800x to do this measuring. Keeping just the center at the
                      maximum value I found gave deminsion to the stars and also maintained colors, otherwise over exposed stars will loose their
                      colors or only have little rings of color around their circunfeneces. Determining the correct exposure for stars also addressed
                      the hot regions of nebulas keeping them from being over exposed, or as over exposed as much, allowing more details to be seen
                      which otherwise would be burned out.

                      I tried reversing my testing, measuring the nebula instead of the stars but this gave me weak flat looking stars. Because stars
                      are constant all over the sky and nebula aren't I returned to measuring stars and live with the few portions of hot nebula.

                      Take some time, have a cup of coffee and formulate your plan for your tests, one night should do it. Save your test images to
                      inspect the next day. You should be able to get a good idea that night but detailed inspection the next day without being
                      interrupted by new exposures will confirm what you may have determined the prior night. Have fun...joe :)

                      ------- Original Message -------
                      From : mandellgl[mailto:gmandell@connecttim: <mailto:gmandell%40connecttime.net> e.net]
                      Sent : 5/1/2007 7:46:49 PM
                      To : ccd-newastro@: <mailto:ccd-newastro%40yahoogroups.com> yahoogroups.com
                      Cc :
                      Subject : RE: [ccd-newastro] Re: Exposure Duration

                      Joe,

                      The resulting subexposure duration is very close whether I use the
                      Starizona or CCDWare calculator.

                      If the estimated duration is 240 sec and I expose for 480 sec, is
                      there a way to tell if I have overexposed the subframe?

                      I am currently using AstroArt 4.0 to measure image statistics.

                      Gordon

                      --- In ccd-newastro@: <mailto:ccd-newastro%40yahoogroups.com> yahoogroups.com, "jmize@..." <jmize@...> wrote:
                      >
                      >
                      > Gordon, go to CCDware's Resources page for their Exposure
                      Calculator, and other tools,
                      > http://www.ccdware.: <http://www.ccdware.com/resources/subexposure.cfm> com/resources/subexposure.cfm You'll probably
                      find the results you'll get here will be similar to the ones
                      > you already gotten using Starzonia's calculator.
                      >
                      > You're now using a CCD Camera specifically designed fot
                      astrophotography, not a DSLR 'modified' for taking pictures of the
                      > stars. The dedicated SVX CCD Camera is much more sensitive and
                      will acquire data much more efficiently. Don't get me wrong,
                      > I've seen some outstanding DSLR images such as the old warhorse
                      film imager and APML'er, Chuck Vaughn whoes images are at
                      > http://www.ccdware.: <http://www.ccdware.com/resources/subexposure.cfm> com/resources/subexposure.cfm
                      >
                      > Being used to exposing film upwards of 90mins I also wanted to
                      expose long. The CCD chip specifically designed for imagery is so
                      > sensitive that the image will be over exposed easily. Have you
                      ever seen images where "all" the stars were pure white? You're
                      > in a diffenernt sensitivity world now.
                      >
                      > If you look into the Archives of this group you'll find several
                      threads discussing exposure durations, short vs long, which
                      > thoroughly discuss all the reasons for one direction or the
                      other. In the long run it's up to you whether you shoot long or
                      > short sub frames...joe :)
                      >
                      >
                      > ------- Original Message -------
                      > From : mandellgl[ mailto:gmandell@...]
                      > Sent : 5/1/2007 1:37:25 AM
                      > To : ccd-newastro@: <mailto:ccd-newastro%40yahoogroups.com> yahoogroups.com
                      > Cc :
                      > Subject : RE: [ccd-newastro] Exposure Duration
                      >
                      > Friends:
                      >
                      > I am using a SXVF-M8C camera in a moderately light-polluted
                      suburban
                      > sky with a Hutech LPS filter.
                      >
                      > I was trying to get an idea how long to expose subframes using a
                      > calculator found on the Starizona website:
                      >
                      > http://starizona.: <http://starizona.com/acb/ccd/calc_ideal.aspx> com/acb/ccd/calc_ideal.aspx
                      >
                      > Based upon the Sky ADU measured with a 3 minute exposure
                      (approximately
                      > 2000) and 5% contribution from readout noise, the calculated
                      > subexposure duration is 4 minutes. That seems kind of short. I
                      was
                      > used to shooting 10-12 minute exposures at the same site using a
                      Canon
                      > EOS 350D camera.
                      >
                      > What is the problem shooting longer subframes than calculated? Is
                      > there another way to estimate subframe duration?
                      >
                      > Gordon Mandell
                      >
                      >
                      >
                      > Yahoo! Groups Links
                      >

                      Yahoo! Groups Links
                    • jmize@svic.net
                      Yup, the STL11K. I though I d mentioned that before, sorry if I didn t...joe :) ... From : Jim Lafferty[mailto:jrlafferty@mycingular.blackberry.net] Sent
                      Message 10 of 16 , May 2, 2007
                      • 0 Attachment
                        Yup, the STL11K. I though I'd mentioned that before, sorry if I didn't...joe :)



                        ------- Original Message -------
                        From : Jim Lafferty[mailto:jrlafferty@...]
                        Sent : 5/2/2007 11:07:28 AM
                        To : ccd-newastro@yahoogroups.com
                        Cc :
                        Subject : RE: Re: [ccd-newastro] Re: Exposure Duration

                        Joe
                        Are you using an anti blooming camera?
                        Jim

                        Jim Lafferty

                        jrlafferty@...
                        shogun000@...

                        -----Original Message-----
                      • sc02492
                        Hi, I have a similar spreadsheet for calculating subexposure duration on my webpage. In my analysis, the sky background ADU must be measured after
                        Message 11 of 16 , May 2, 2007
                        • 0 Attachment
                          Hi, I have a similar spreadsheet for calculating subexposure duration
                          on my webpage. In my analysis, the sky background ADU must be
                          measured after calibration. If I'm not mistaken, the same is required
                          for John Smith's subexposure calculator as well.

                          Steve

                          Steve Cannistra
                          http://www.starrywonders.com

                          --- In ccd-newastro@yahoogroups.com, "mandellgl" <gmandell@...> wrote:
                          >
                          > Neil,
                          >
                          > I was measuring pre-calibrated background ADU.
                          >
                          > Gordon
                          >
                          > --- In ccd-newastro@yahoogroups.com, Neil Fleming <neilfleming@>
                          > wrote:
                          > >
                          > > My only question would be is this supposed to be a
                          > > pre-calibration or post-calibration background
                          > > statistic?
                          > >
                          > > ...Neil
                          > >
                          > > --- mandellgl <gmandell@> wrote:
                          > >
                          > > > Friends:
                          > > >
                          > > > I am using a SXVF-M8C camera in a moderately
                          > > > light-polluted suburban
                          > > > sky with a Hutech LPS filter.
                          > > >
                          > > > I was trying to get an idea how long to expose
                          > > > subframes using a
                          > > > calculator found on the Starizona website:
                          > > >
                          > > > http://starizona.com/acb/ccd/calc_ideal.aspx
                          > > >
                          > > > Based upon the Sky ADU measured with a 3 minute
                          > > > exposure (approximately
                          > > > 2000) and 5% contribution from readout noise, the
                          > > > calculated
                          > > > subexposure duration is 4 minutes. That seems kind
                          > > > of short. I was
                          > > > used to shooting 10-12 minute exposures at the same
                          > > > site using a Canon
                          > > > EOS 350D camera.
                          > > >
                          > > > What is the problem shooting longer subframes than
                          > > > calculated? Is
                          > > > there another way to estimate subframe duration?
                          > > >
                          > > > Gordon Mandell
                          > > >
                          > > >
                          > >
                          > >
                          > > www.flemingastrophotography.com
                          > > Direct from Boston - brilliant diamonds in pea soup
                          > >
                          >
                        • Yahoo - Wodaski
                          Calibration would be required for any sub-exposure calculation. The dark current is unwanted signal which must be removed, and has nothing whatsoever to do
                          Message 12 of 16 , May 2, 2007
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                            Calibration would be required for any sub-exposure calculation. The dark
                            current is unwanted signal which must be removed, and has nothing
                            whatsoever to do with the calculation.

                            Ron W

                            sc02492 wrote:
                            > Hi, I have a similar spreadsheet for calculating subexposure duration
                            > on my webpage. In my analysis, the sky background ADU must be
                            > measured after calibration. If I'm not mistaken, the same is required
                            > for John Smith's subexposure calculator as well.
                            >
                            > Steve
                            >
                            > Steve Cannistra
                            > http://www.starrywonders.com
                            >
                            > --- In ccd-newastro@yahoogroups.com, "mandellgl" <gmandell@...> wrote:
                            >
                            >> Neil,
                            >>
                            >> I was measuring pre-calibrated background ADU.
                            >>
                            >> Gordon
                            >>
                            >> --- In ccd-newastro@yahoogroups.com, Neil Fleming <neilfleming@>
                            >> wrote:
                            >>
                            >>> My only question would be is this supposed to be a
                            >>> pre-calibration or post-calibration background
                            >>> statistic?
                            >>>
                            >>> ...Neil
                            >>>
                            >>> --- mandellgl <gmandell@> wrote:
                            >>>
                            >>>
                            >>>> Friends:
                            >>>>
                            >>>> I am using a SXVF-M8C camera in a moderately
                            >>>> light-polluted suburban
                            >>>> sky with a Hutech LPS filter.
                            >>>>
                            >>>> I was trying to get an idea how long to expose
                            >>>> subframes using a
                            >>>> calculator found on the Starizona website:
                            >>>>
                            >>>> http://starizona.com/acb/ccd/calc_ideal.aspx
                            >>>>
                            >>>> Based upon the Sky ADU measured with a 3 minute
                            >>>> exposure (approximately
                            >>>> 2000) and 5% contribution from readout noise, the
                            >>>> calculated
                            >>>> subexposure duration is 4 minutes. That seems kind
                            >>>> of short. I was
                            >>>> used to shooting 10-12 minute exposures at the same
                            >>>> site using a Canon
                            >>>> EOS 350D camera.
                            >>>>
                            >>>> What is the problem shooting longer subframes than
                            >>>> calculated? Is
                            >>>> there another way to estimate subframe duration?
                            >>>>
                            >>>> Gordon Mandell
                            >>>>
                            >>>>
                            >>>>
                            >>> www.flemingastrophotography.com
                            >>> Direct from Boston - brilliant diamonds in pea soup
                            >>>
                            >>>
                            >
                            >
                            >
                            >
                            > Yahoo! Groups Links
                            >
                            >
                            >
                            >
                          • Neil Fleming
                            That s what I thought. The pre-calibration numbers ended up being really short . ... www.flemingastrophotography.com Direct from Boston - brilliant
                            Message 13 of 16 , May 2, 2007
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                              That's what I thought. The pre-calibration numbers
                              ended up being really short <g>.

                              ...Neil

                              --- sc02492 <sc02492@...> wrote:

                              > Hi, I have a similar spreadsheet for calculating
                              > subexposure duration
                              > on my webpage. In my analysis, the sky background
                              > ADU must be
                              > measured after calibration. If I'm not mistaken,
                              > the same is required
                              > for John Smith's subexposure calculator as well.
                              >
                              > Steve
                              >
                              > Steve Cannistra
                              > http://www.starrywonders.com
                              >
                              > --- In ccd-newastro@yahoogroups.com, "mandellgl"
                              > <gmandell@...> wrote:
                              > >
                              > > Neil,
                              > >
                              > > I was measuring pre-calibrated background ADU.
                              > >
                              > > Gordon
                              > >
                              > > --- In ccd-newastro@yahoogroups.com, Neil Fleming
                              > <neilfleming@>
                              > > wrote:
                              > > >
                              > > > My only question would be is this supposed to be
                              > a
                              > > > pre-calibration or post-calibration background
                              > > > statistic?
                              > > >
                              > > > ...Neil
                              > > >
                              > > > --- mandellgl <gmandell@> wrote:
                              > > >
                              > > > > Friends:
                              > > > >
                              > > > > I am using a SXVF-M8C camera in a moderately
                              > > > > light-polluted suburban
                              > > > > sky with a Hutech LPS filter.
                              > > > >
                              > > > > I was trying to get an idea how long to expose
                              > > > > subframes using a
                              > > > > calculator found on the Starizona website:
                              > > > >
                              > > > > http://starizona.com/acb/ccd/calc_ideal.aspx
                              > > > >
                              > > > > Based upon the Sky ADU measured with a 3
                              > minute
                              > > > > exposure (approximately
                              > > > > 2000) and 5% contribution from readout noise,
                              > the
                              > > > > calculated
                              > > > > subexposure duration is 4 minutes. That seems
                              > kind
                              > > > > of short. I was
                              > > > > used to shooting 10-12 minute exposures at the
                              > same
                              > > > > site using a Canon
                              > > > > EOS 350D camera.
                              > > > >
                              > > > > What is the problem shooting longer subframes
                              > than
                              > > > > calculated? Is
                              > > > > there another way to estimate subframe
                              > duration?
                              > > > >
                              > > > > Gordon Mandell
                              > > > >
                              > > > >
                              > > >
                              > > >
                              > > > www.flemingastrophotography.com
                              > > > Direct from Boston - brilliant diamonds in pea
                              > soup
                              > > >
                              > >
                              >
                              >
                              >


                              www.flemingastrophotography.com
                              Direct from Boston - brilliant diamonds in pea soup
                            • mandellgl
                              Joe: Thank you for your detailed insights. I have so few opportunities to image, I hate to use those precious momments to run tests. But I guess that s the
                              Message 14 of 16 , May 3, 2007
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                                Joe:

                                Thank you for your detailed insights. I have so few opportunities to
                                image, I "hate" to use those precious momments to run tests. But I
                                guess that's the nature of this hobby. Each imaging setup is unique
                                enough that although general guidelines are helpful, precise answers
                                will always require test sessions.

                                Gordon


                                --- In ccd-newastro@yahoogroups.com, "jmize@..." <jmize@...> wrote:
                                >
                                > Gordon you appear to understand the 'minimum' exposure calculators
                                the way I do, they suggest the 'minumum' exposure to get above
                                > shot and camera noise. Your question was the same as mine when I
                                first went there, find out how 'long' I should expose my
                                > images. Not so, these tools are not for that purpose.
                                >
                                > What I ended up doing was to find a rich object of both stars and
                                nebula to run some tests. I started with my 'minimum'
                                > suggested exposure of 6.7mins and took a series of exposures
                                progressivly longer. As the images came in I calibrated them and
                                > inspected them.
                                >
                                > As the exposures got longer I noted there was more fainter nebula,
                                but the brightest portions of the nebula were being burned out
                                > and the brightest stars were getting ragged and bloating from being
                                over exposed. Something I learned from film work was just as
                                > if something was out of focuse, if something was over exposed
                                there's not much you could do about it.
                                >
                                > I settled upon two RGB exposure times for my setup, 10 and 15mins.
                                10mins images for subjects with bright stars and hot nebula
                                > and 15mins for objects with few/no bright stars and no hot nebula
                                portions that would over expose. 90% of the time I use 10mins
                                > exposures.
                                >
                                > I know nothing about AstroArt, I used Photoshop checking the
                                intensities of the brightest star/s. You want the centers to 'just'
                                > be reaching 255, not the entire star diameter being 255. Zoom in
                                to 6-800x to do this measuring. Keeping just the center at the
                                > maximum value I found gave deminsion to the stars and also
                                maintained colors, otherwise over exposed stars will loose their
                                > colors or only have little rings of color around their
                                circunfeneces. Determining the correct exposure for stars also
                                addressed
                                > the hot regions of nebulas keeping them from being over exposed, or
                                as over exposed as much, allowing more details to be seen
                                > which otherwise would be burned out.
                                >
                                > I tried reversing my testing, measuring the nebula instead of the
                                stars but this gave me weak flat looking stars. Because stars
                                > are constant all over the sky and nebula aren't I returned to
                                measuring stars and live with the few portions of hot nebula.
                                >
                                > Take some time, have a cup of coffee and formulate your plan for
                                your tests, one night should do it. Save your test images to
                                > inspect the next day. You should be able to get a good idea that
                                night but detailed inspection the next day without being
                                > interrupted by new exposures will confirm what you may have
                                determined the prior night. Have fun...joe :)
                                >
                                >
                                > ------- Original Message -------
                                > From : mandellgl[mailto:gmandell@...]
                                > Sent : 5/1/2007 7:46:49 PM
                                > To : ccd-newastro@yahoogroups.com
                                > Cc :
                                > Subject : RE: [ccd-newastro] Re: Exposure Duration
                                >
                                > Joe,
                                >
                                > The resulting subexposure duration is very close whether I use the
                                > Starizona or CCDWare calculator.
                                >
                                > If the estimated duration is 240 sec and I expose for 480 sec, is
                                > there a way to tell if I have overexposed the subframe?
                                >
                                > I am currently using AstroArt 4.0 to measure image statistics.
                                >
                                > Gordon
                                >
                                > --- In ccd-newastro@yahoogroups.com, "jmize@" <jmize@> wrote:
                                > >
                                > >
                                > > Gordon, go to CCDware's Resources page for their Exposure
                                > Calculator, and other tools,
                                > > http://www.ccdware.com/resources/subexposure.cfm You'll
                                probably
                                > find the results you'll get here will be similar to the ones
                                > > you already gotten using Starzonia's calculator.
                                > >
                                > > You're now using a CCD Camera specifically designed fot
                                > astrophotography, not a DSLR 'modified' for taking pictures of the
                                > > stars. The dedicated SVX CCD Camera is much more sensitive and
                                > will acquire data much more efficiently. Don't get me wrong,
                                > > I've seen some outstanding DSLR images such as the old warhorse
                                > film imager and APML'er, Chuck Vaughn whoes images are at
                                > > http://www.ccdware.com/resources/subexposure.cfm
                                > >
                                > > Being used to exposing film upwards of 90mins I also wanted to
                                > expose long. The CCD chip specifically designed for imagery is so
                                > > sensitive that the image will be over exposed easily. Have you
                                > ever seen images where "all" the stars were pure white? You're
                                > > in a diffenernt sensitivity world now.
                                > >
                                > > If you look into the Archives of this group you'll find several
                                > threads discussing exposure durations, short vs long, which
                                > > thoroughly discuss all the reasons for one direction or the
                                > other. In the long run it's up to you whether you shoot long or
                                > > short sub frames...joe :)
                                > >
                                > >
                                > > ------- Original Message -------
                                > > From : mandellgl[ mailto:gmandell@]
                                > > Sent : 5/1/2007 1:37:25 AM
                                > > To : ccd-newastro@yahoogroups.com
                                > > Cc :
                                > > Subject : RE: [ccd-newastro] Exposure Duration
                                > >
                                > > Friends:
                                > >
                                > > I am using a SXVF-M8C camera in a moderately light-polluted
                                > suburban
                                > > sky with a Hutech LPS filter.
                                > >
                                > > I was trying to get an idea how long to expose subframes using a
                                > > calculator found on the Starizona website:
                                > >
                                > > http://starizona.com/acb/ccd/calc_ideal.aspx
                                > >
                                > > Based upon the Sky ADU measured with a 3 minute exposure
                                > (approximately
                                > > 2000) and 5% contribution from readout noise, the calculated
                                > > subexposure duration is 4 minutes. That seems kind of short. I
                                > was
                                > > used to shooting 10-12 minute exposures at the same site using a
                                > Canon
                                > > EOS 350D camera.
                                > >
                                > > What is the problem shooting longer subframes than calculated?
                                Is
                                > > there another way to estimate subframe duration?
                                > >
                                > > Gordon Mandell
                                > >
                                > >
                                > >
                                > > Yahoo! Groups Links
                                > >
                                >
                                >
                                >
                                >
                                > Yahoo! Groups Links
                                >
                              • mandellgl
                                Ron, With the low noise levels of the Starlight Xpress cameras, would dark calibration still be necessary for accurate exposure calculations? I am using a
                                Message 15 of 16 , May 3, 2007
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                                  Ron,

                                  With the low noise levels of the Starlight Xpress cameras, would dark
                                  calibration still be necessary for accurate exposure calculations? I
                                  am using a one-shot ccd camera (SXVF-M8C); should I Bayer interpolate
                                  the test exposure before measuring background ADU?

                                  Gordon

                                  --- In ccd-newastro@yahoogroups.com, Yahoo - Wodaski <yahoo@...>
                                  wrote:
                                  >
                                  > Calibration would be required for any sub-exposure calculation. The
                                  dark
                                  > current is unwanted signal which must be removed, and has nothing
                                  > whatsoever to do with the calculation.
                                  >
                                  > Ron W
                                  >
                                  > sc02492 wrote:
                                  > > Hi, I have a similar spreadsheet for calculating subexposure
                                  duration
                                  > > on my webpage. In my analysis, the sky background ADU must be
                                  > > measured after calibration. If I'm not mistaken, the same is
                                  required
                                  > > for John Smith's subexposure calculator as well.
                                  > >
                                  > > Steve
                                  > >
                                  > > Steve Cannistra
                                  > > http://www.starrywonders.com
                                  > >
                                  > > --- In ccd-newastro@yahoogroups.com, "mandellgl" <gmandell@>
                                  wrote:
                                  > >
                                  > >> Neil,
                                  > >>
                                  > >> I was measuring pre-calibrated background ADU.
                                  > >>
                                  > >> Gordon
                                  > >>
                                  > >> --- In ccd-newastro@yahoogroups.com, Neil Fleming <neilfleming@>
                                  > >> wrote:
                                  > >>
                                  > >>> My only question would be is this supposed to be a
                                  > >>> pre-calibration or post-calibration background
                                  > >>> statistic?
                                  > >>>
                                  > >>> ...Neil
                                  > >>>
                                  > >>> --- mandellgl <gmandell@> wrote:
                                  > >>>
                                  > >>>
                                  > >>>> Friends:
                                  > >>>>
                                  > >>>> I am using a SXVF-M8C camera in a moderately
                                  > >>>> light-polluted suburban
                                  > >>>> sky with a Hutech LPS filter.
                                  > >>>>
                                  > >>>> I was trying to get an idea how long to expose
                                  > >>>> subframes using a
                                  > >>>> calculator found on the Starizona website:
                                  > >>>>
                                  > >>>> http://starizona.com/acb/ccd/calc_ideal.aspx
                                  > >>>>
                                  > >>>> Based upon the Sky ADU measured with a 3 minute
                                  > >>>> exposure (approximately
                                  > >>>> 2000) and 5% contribution from readout noise, the
                                  > >>>> calculated
                                  > >>>> subexposure duration is 4 minutes. That seems kind
                                  > >>>> of short. I was
                                  > >>>> used to shooting 10-12 minute exposures at the same
                                  > >>>> site using a Canon
                                  > >>>> EOS 350D camera.
                                  > >>>>
                                  > >>>> What is the problem shooting longer subframes than
                                  > >>>> calculated? Is
                                  > >>>> there another way to estimate subframe duration?
                                  > >>>>
                                  > >>>> Gordon Mandell
                                  > >>>>
                                  > >>>>
                                  > >>>>
                                  > >>> www.flemingastrophotography.com
                                  > >>> Direct from Boston - brilliant diamonds in pea soup
                                  > >>>
                                  > >>>
                                  > >
                                  > >
                                  > >
                                  > >
                                  > > Yahoo! Groups Links
                                  > >
                                  > >
                                  > >
                                  > >
                                  >
                                • Yahoo - Wodaski
                                  It does depend on the magnitude of the dark current - you can get that information from Starlight XPress. As to the Bayer interpolation, you would have to ask
                                  Message 16 of 16 , May 3, 2007
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                                    It does depend on the magnitude of the dark current - you can get that
                                    information from Starlight XPress.

                                    As to the Bayer interpolation, you would have to ask the person who
                                    created the calculator. I think that a Bayer matrix gets in the way
                                    since de-Bayering normalizes the color data (changes the values). I
                                    don't know how you would do this for a one-shot color camera, or even
                                    whether the calculators that are out there support it. You would have to
                                    ask the person who created a given calculator if they support your
                                    camera, and if so, what the rules are.

                                    Ron W

                                    mandellgl wrote:
                                    > Ron,
                                    >
                                    > With the low noise levels of the Starlight Xpress cameras, would dark
                                    > calibration still be necessary for accurate exposure calculations? I
                                    > am using a one-shot ccd camera (SXVF-M8C); should I Bayer interpolate
                                    > the test exposure before measuring background ADU?
                                    >
                                    > Gordon
                                    >
                                    > --- In ccd-newastro@yahoogroups.com, Yahoo - Wodaski <yahoo@...>
                                    > wrote:
                                    >
                                    >> Calibration would be required for any sub-exposure calculation. The
                                    >>
                                    > dark
                                    >
                                    >> current is unwanted signal which must be removed, and has nothing
                                    >> whatsoever to do with the calculation.
                                    >>
                                    >> Ron W
                                    >>
                                    >> sc02492 wrote:
                                    >>
                                    >>> Hi, I have a similar spreadsheet for calculating subexposure
                                    >>>
                                    > duration
                                    >
                                    >>> on my webpage. In my analysis, the sky background ADU must be
                                    >>> measured after calibration. If I'm not mistaken, the same is
                                    >>>
                                    > required
                                    >
                                    >>> for John Smith's subexposure calculator as well.
                                    >>>
                                    >>> Steve
                                    >>>
                                    >>> Steve Cannistra
                                    >>> http://www.starrywonders.com
                                    >>>
                                    >>> --- In ccd-newastro@yahoogroups.com, "mandellgl" <gmandell@>
                                    >>>
                                    > wrote:
                                    >
                                    >>>
                                    >>>
                                    >>>> Neil,
                                    >>>>
                                    >>>> I was measuring pre-calibrated background ADU.
                                    >>>>
                                    >>>> Gordon
                                    >>>>
                                    >>>> --- In ccd-newastro@yahoogroups.com, Neil Fleming <neilfleming@>
                                    >>>> wrote:
                                    >>>>
                                    >>>>
                                    >>>>> My only question would be is this supposed to be a
                                    >>>>> pre-calibration or post-calibration background
                                    >>>>> statistic?
                                    >>>>>
                                    >>>>> ...Neil
                                    >>>>>
                                    >>>>> --- mandellgl <gmandell@> wrote:
                                    >>>>>
                                    >>>>>
                                    >>>>>
                                    >>>>>> Friends:
                                    >>>>>>
                                    >>>>>> I am using a SXVF-M8C camera in a moderately
                                    >>>>>> light-polluted suburban
                                    >>>>>> sky with a Hutech LPS filter.
                                    >>>>>>
                                    >>>>>> I was trying to get an idea how long to expose
                                    >>>>>> subframes using a
                                    >>>>>> calculator found on the Starizona website:
                                    >>>>>>
                                    >>>>>> http://starizona.com/acb/ccd/calc_ideal.aspx
                                    >>>>>>
                                    >>>>>> Based upon the Sky ADU measured with a 3 minute
                                    >>>>>> exposure (approximately
                                    >>>>>> 2000) and 5% contribution from readout noise, the
                                    >>>>>> calculated
                                    >>>>>> subexposure duration is 4 minutes. That seems kind
                                    >>>>>> of short. I was
                                    >>>>>> used to shooting 10-12 minute exposures at the same
                                    >>>>>> site using a Canon
                                    >>>>>> EOS 350D camera.
                                    >>>>>>
                                    >>>>>> What is the problem shooting longer subframes than
                                    >>>>>> calculated? Is
                                    >>>>>> there another way to estimate subframe duration?
                                    >>>>>>
                                    >>>>>> Gordon Mandell
                                    >>>>>>
                                    >>>>>>
                                    >>>>>>
                                    >>>>>>
                                    >>>>> www.flemingastrophotography.com
                                    >>>>> Direct from Boston - brilliant diamonds in pea soup
                                    >>>>>
                                    >>>>>
                                    >>>>>
                                    >>>
                                    >>>
                                    >>> Yahoo! Groups Links
                                    >>>
                                    >>>
                                    >>>
                                    >>>
                                    >>>
                                    >
                                    >
                                    >
                                    >
                                    > Yahoo! Groups Links
                                    >
                                    >
                                    >
                                    >
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