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66166Re: Manually reduction paradox

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  • lbarneo2003
    Nov 3, 2009
      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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