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RE: [ccd-newastro] Exposure Duration

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  • 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 1 of 16 , May 1 5:59 AM
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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 2 of 16 , May 1 6:55 AM
      • 0 Attachment
        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 3 of 16 , May 1 7:45 AM
        • 0 Attachment
          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 4 of 16 , May 1 8:58 AM
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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 5 of 16 , May 1 4:43 PM
            • 0 Attachment
              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 6 of 16 , May 1 4:46 PM
              • 0 Attachment
                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 7 of 16 , May 2 6:58 AM
                • 0 Attachment
                  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 8 of 16 , May 2 8:07 AM
                  • 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 9 of 16 , May 2 8:58 AM
                    • 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 10 of 16 , May 2 10:08 AM
                      • 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 11 of 16 , May 2 10:36 AM
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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 12 of 16 , May 2 9:25 PM
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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 13 of 16 , May 3 2:34 AM
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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 14 of 16 , May 3 2:39 AM
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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 15 of 16 , May 3 7:22 AM
                                • 0 Attachment
                                  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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