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Manually reduction paradox

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  • lbarneo2003
    Ron, Recently I bought a SBIG-402 ME ccd camera, and it woks very well. I known that for scientific purpose the best option for image reduction it is those
    Message 1 of 6 , Nov 3, 2009
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      Ron,
      Recently I bought a SBIG-402 ME ccd camera, and it woks very well. I known that for scientific purpose the best option for image reduction it is those that you explain in your book (section 2: using dark frames): "…to take one or two dark frames before your light exposure, then another one or two after, and average the dark frames…" And this is handy when your exposure time is less than 3 min (usually in photometry/,astrometry). But if you want to take a "postal" image that requires a lot of exposure time, this procedure is not very practice, and one solution is to use dark frames that previously have been taken (same temperature, exposition time). And this is my problem: I have a paradox when I perform a manual combine. When I apply it in drak substraction (CCDOPS), the dark frame seems to"eat" the image frame. I have some test in a dark room. When I apply the automatic reduction, all works very well. When I take a dark frame, and perform the dark substraction, the image disappear or almost: all is black. This is very significant using short exposures (less than 120 seconds). Could you explain me this difference? With CCDSoft this effect is similar. You can see the images in album photo: Testdarkroom. Thanks
      Luis
    • Wodaski - Yahoo
      Well, let s consider the obvious first. Are you using automatic contrast adjustment? If you don t, then applying a dark will radically alter the appearance of
      Message 2 of 6 , Nov 3, 2009
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        Well, let's consider the obvious first. Are you using automatic
        contrast adjustment? If you don't, then applying a dark will radically
        alter the appearance of the image. Depending on the new values, yes,
        you could see all or most of the data 'disappear'. It's still there;
        you just need to adjust contrast/blackpoint/whatever your software
        calls it. <g>

        Ron W

        On Nov 3, 2009, at 1:00 PM, lbarneo2003 wrote:

        > Ron,
        > Recently I bought a SBIG-402 ME ccd camera, and it woks very well. I
        > known that for scientific purpose the best option for image
        > reduction it is those that you explain in your book (section 2:
        > using dark frames): "…to take one or two dark frames before your
        > light exposure, then another one or two after, and average the dark
        > frames…" And this is handy when your exposure time is less than 3
        > min (usually in photometry/,astrometry). But if you want to take a
        > "postal" image that requires a lot of exposure time, this procedure
        > is not very practice, and one solution is to use dark frames that
        > previously have been taken (same temperature, exposition time). And
        > this is my problem: I have a paradox when I perform a manual
        > combine. When I apply it in drak substraction (CCDOPS), the dark
        > frame seems to"eat" the image frame. I have some test in a dark
        > room. When I apply the automatic reduction, all works very well.
        > When I take a dark frame, and perform the dark substraction, the
        > image disappear or almost: all is black. This is very significant
        > using short exposures (less than 120 seconds). Could you explain me
        > this difference? With CCDSoft this effect is similar. You can see
        > the images in album photo: Testdarkroom. Thanks
        > Luis
        >
        >
        >
        >
        > ------------------------------------
        >
        >
        >
        >
      • lbarneo2003
        Thanks Rons, Really!!, I had unchecked the auto contrast. I just do it now, and the image appears.Do I need to do something with back and range values in the
        Message 3 of 6 , Nov 3, 2009
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          Thanks Rons,
          Really!!, I had unchecked the auto contrast. I just do it now, and the image appears.Do I need to do something with back and range values in the contrast window?
          Luis

          --- In ccd-newastro@yahoogroups.com, Wodaski - Yahoo <yahoo@...> wrote:
          >
          > Well, let's consider the obvious first. Are you using automatic
          > contrast adjustment? If you don't, then applying a dark will radically
          > alter the appearance of the image. Depending on the new values, yes,
          > you could see all or most of the data 'disappear'. It's still there;
          > you just need to adjust contrast/blackpoint/whatever your software
          > calls it. <g>
          >
          > Ron W
          >
          > On Nov 3, 2009, at 1:00 PM, lbarneo2003 wrote:
          >
          > > Ron,
          > > Recently I bought a SBIG-402 ME ccd camera, and it woks very well. I
          > > known that for scientific purpose the best option for image
          > > reduction it is those that you explain in your book (section 2:
          > > using dark frames): "…to take one or two dark frames before your
          > > light exposure, then another one or two after, and average the dark
          > > frames…" And this is handy when your exposure time is less than 3
          > > min (usually in photometry/,astrometry). But if you want to take a
          > > "postal" image that requires a lot of exposure time, this procedure
          > > is not very practice, and one solution is to use dark frames that
          > > previously have been taken (same temperature, exposition time). And
          > > this is my problem: I have a paradox when I perform a manual
          > > combine. When I apply it in drak substraction (CCDOPS), the dark
          > > frame seems to"eat" the image frame. I have some test in a dark
          > > room. When I apply the automatic reduction, all works very well.
          > > When I take a dark frame, and perform the dark substraction, the
          > > image disappear or almost: all is black. This is very significant
          > > using short exposures (less than 120 seconds). Could you explain me
          > > this difference? With CCDSoft this effect is similar. You can see
          > > the images in album photo: Testdarkroom. Thanks
          > > Luis
          > >
          > >
          > >
          > >
          > > ------------------------------------
          > >
          > >
          > >
          > >
          >
        • lbarneo2003
          Thanks Rons, Really!!, I had unchecked the auto contrast. I just do it now, and the image appears.Do I need to do something with back and range values in the
          Message 4 of 6 , Nov 3, 2009
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            Thanks Rons,
            Really!!, I had unchecked the auto contrast. I just do it now, and the image appears.Do I need to do something with back and range values in the contrast window?
            Luis

            --- In ccd-newastro@yahoogroups.com, Wodaski - Yahoo <yahoo@...> wrote:
            >
            > Well, let's consider the obvious first. Are you using automatic
            > contrast adjustment? If you don't, then applying a dark will radically
            > alter the appearance of the image. Depending on the new values, yes,
            > you could see all or most of the data 'disappear'. It's still there;
            > you just need to adjust contrast/blackpoint/whatever your software
            > calls it. <g>
            >
            > Ron W
            >
            > On Nov 3, 2009, at 1:00 PM, lbarneo2003 wrote:
            >
            > > Ron,
            > > Recently I bought a SBIG-402 ME ccd camera, and it woks very well. I
            > > known that for scientific purpose the best option for image
            > > reduction it is those that you explain in your book (section 2:
            > > using dark frames): "…to take one or two dark frames before your
            > > light exposure, then another one or two after, and average the dark
            > > frames…" And this is handy when your exposure time is less than 3
            > > min (usually in photometry/,astrometry). But if you want to take a
            > > "postal" image that requires a lot of exposure time, this procedure
            > > is not very practice, and one solution is to use dark frames that
            > > previously have been taken (same temperature, exposition time). And
            > > this is my problem: I have a paradox when I perform a manual
            > > combine. When I apply it in drak substraction (CCDOPS), the dark
            > > frame seems to"eat" the image frame. I have some test in a dark
            > > room. When I apply the automatic reduction, all works very well.
            > > When I take a dark frame, and perform the dark substraction, the
            > > image disappear or almost: all is black. This is very significant
            > > using short exposures (less than 120 seconds). Could you explain me
            > > this difference? With CCDSoft this effect is similar. You can see
            > > the images in album photo: Testdarkroom. Thanks
            > > Luis
            > >
            > >
            > >
            > >
            > > ------------------------------------
            > >
            > >
            > >
            > >
            >
          • Wodaski - Yahoo
            CCDOPS doesn t really process the image. Back and range are just black and white point settings; all of the data is still here. You can do some real
            Message 5 of 6 , Nov 3, 2009
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              CCDOPS doesn't really 'process' the image. Back and range are just
              black and white point settings; all of the data is still here. You can
              do some real processing in Photoshop, CCDSoft, MaxIm DL, CCDStack, or
              whatever software you choose. CCDOPS is _very_ limited in terms of
              processing.

              Ron W

              On Nov 3, 2009, at 3:50 PM, lbarneo2003 wrote:

              > Thanks Rons,
              > Really!!, I had unchecked the auto contrast. I just do it now, and
              > the image appears.Do I need to do something with back and range
              > values in the contrast window?
              > Luis
              >
              > --- In ccd-newastro@yahoogroups.com, Wodaski - Yahoo <yahoo@...>
              > wrote:
              >>
              >> Well, let's consider the obvious first. Are you using automatic
              >> contrast adjustment? If you don't, then applying a dark will
              >> radically
              >> alter the appearance of the image. Depending on the new values, yes,
              >> you could see all or most of the data 'disappear'. It's still there;
              >> you just need to adjust contrast/blackpoint/whatever your software
              >> calls it. <g>
              >>
              >> Ron W
              >>
              >> On Nov 3, 2009, at 1:00 PM, lbarneo2003 wrote:
              >>
              >>> Ron,
              >>> Recently I bought a SBIG-402 ME ccd camera, and it woks very well. I
              >>> known that for scientific purpose the best option for image
              >>> reduction it is those that you explain in your book (section 2:
              >>> using dark frames): "…to take one or two dark frames before your
              >>> light exposure, then another one or two after, and average the dark
              >>> frames…" And this is handy when your exposure time is less than 3
              >>> min (usually in photometry/,astrometry). But if you want to take a
              >>> "postal" image that requires a lot of exposure time, this procedure
              >>> is not very practice, and one solution is to use dark frames that
              >>> previously have been taken (same temperature, exposition time). And
              >>> this is my problem: I have a paradox when I perform a manual
              >>> combine. When I apply it in drak substraction (CCDOPS), the dark
              >>> frame seems to"eat" the image frame. I have some test in a dark
              >>> room. When I apply the automatic reduction, all works very well.
              >>> When I take a dark frame, and perform the dark substraction, the
              >>> image disappear or almost: all is black. This is very significant
              >>> using short exposures (less than 120 seconds). Could you explain me
              >>> this difference? With CCDSoft this effect is similar. You can see
              >>> the images in album photo: Testdarkroom. Thanks
              >>> Luis
              >>>
              >>>
              >>>
              >>>
              >>> ------------------------------------
              >>>
              >>>
              >>>
              >>>
              >>
              >
              >
              >
              >
              > ------------------------------------
              >
              >
              >
              >
            • lbarneo2003
              OK, thanks, Luis
              Message 6 of 6 , Nov 3, 2009
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                OK, thanks,
                Luis

                --- In ccd-newastro@yahoogroups.com, Wodaski - Yahoo <yahoo@...> wrote:
                >
                > CCDOPS doesn't really 'process' the image. Back and range are just
                > black and white point settings; all of the data is still here. You can
                > do some real processing in Photoshop, CCDSoft, MaxIm DL, CCDStack, or
                > whatever software you choose. CCDOPS is _very_ limited in terms of
                > processing.
                >
                > Ron W
                >
                > On Nov 3, 2009, at 3:50 PM, lbarneo2003 wrote:
                >
                > > Thanks Rons,
                > > Really!!, I had unchecked the auto contrast. I just do it now, and
                > > the image appears.Do I need to do something with back and range
                > > values in the contrast window?
                > > Luis
                > >
                > > --- In ccd-newastro@yahoogroups.com, Wodaski - Yahoo <yahoo@>
                > > wrote:
                > >>
                > >> Well, let's consider the obvious first. Are you using automatic
                > >> contrast adjustment? If you don't, then applying a dark will
                > >> radically
                > >> alter the appearance of the image. Depending on the new values, yes,
                > >> you could see all or most of the data 'disappear'. It's still there;
                > >> you just need to adjust contrast/blackpoint/whatever your software
                > >> calls it. <g>
                > >>
                > >> Ron W
                > >>
                > >> On Nov 3, 2009, at 1:00 PM, lbarneo2003 wrote:
                > >>
                > >>> Ron,
                > >>> Recently I bought a SBIG-402 ME ccd camera, and it woks very well. I
                > >>> known that for scientific purpose the best option for image
                > >>> reduction it is those that you explain in your book (section 2:
                > >>> using dark frames): "…to take one or two dark frames before your
                > >>> light exposure, then another one or two after, and average the dark
                > >>> frames…" And this is handy when your exposure time is less than 3
                > >>> min (usually in photometry/,astrometry). But if you want to take a
                > >>> "postal" image that requires a lot of exposure time, this procedure
                > >>> is not very practice, and one solution is to use dark frames that
                > >>> previously have been taken (same temperature, exposition time). And
                > >>> this is my problem: I have a paradox when I perform a manual
                > >>> combine. When I apply it in drak substraction (CCDOPS), the dark
                > >>> frame seems to"eat" the image frame. I have some test in a dark
                > >>> room. When I apply the automatic reduction, all works very well.
                > >>> When I take a dark frame, and perform the dark substraction, the
                > >>> image disappear or almost: all is black. This is very significant
                > >>> using short exposures (less than 120 seconds). Could you explain me
                > >>> this difference? With CCDSoft this effect is similar. You can see
                > >>> the images in album photo: Testdarkroom. Thanks
                > >>> Luis
                > >>>
                > >>>
                > >>>
                > >>>
                > >>> ------------------------------------
                > >>>
                > >>>
                > >>>
                > >>>
                > >>
                > >
                > >
                > >
                > >
                > > ------------------------------------
                > >
                > >
                > >
                > >
                >
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