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Re: Narrowband with an OSC

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  • Stan
    ... Please take no offense. That statement is meant as a warning. The malpractice is on the part of marketers for misleading customers (at the very least by
    Message 1 of 13 , Nov 22, 2012
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      --- Orlando Andico <orly.andico@...> wrote:
      > I find the statement that an OSC is "malpractice" for
      > narrow-band seems a bit extreme.

      Please take no offense. That statement is meant as a warning. The "malpractice" is on the part of marketers for misleading customers (at the very least by failing to educate naive users). I'm sure there are some satisfied "astro" OSC uses but many come to regret that choice. And many OSC'ers don't know what they are missing or have limited ambitions for small fast scopes on large bright objects (that would do almost as well with DSLR). But this only a hobby and people should have fun – so if OSC appeals to you (even erroneously) then enjoy!

      > OSC - the QHY8 - and it has 50% QE in H-alpha.

      Actually that detector's QE is only 12.5% for H-a. 75% of the OSC pixels are completely blind to H-a (0% QE) and the remaining 25% of the pixels only detect 50% of H-a.

      0.25 x 0.5 = 0.125

      > a good number of great H-alpha images with this OSC.

      13% QE is in the higher range of film emulsions, which used to be the only way to take astro-photos...

      Stan
    • Randy
      Hi Stan, You make a good point. I have a Takahashi FSQ106ED working at around F5 (or close to that). I also have a Celestron 11 SCT at F10. I do have an
      Message 2 of 13 , Nov 22, 2012
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        Hi Stan,

        You make a good point. I have a Takahashi FSQ106ED working at around F5 (or close to that). I also have a Celestron 11" SCT at F10. I do have an extender for the FSQ and a reducer for the 11" so I have a little variability. Is there a mono CCD that I could use that would do OK with both?

        Thanks,

        Randy

        --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@...> wrote:
        >
        > --- Orlando Andico <orly.andico@> wrote:
        > > I find the statement that an OSC is "malpractice" for
        > > narrow-band seems a bit extreme.
        >
        > Please take no offense. That statement is meant as a warning. The "malpractice" is on the part of marketers for misleading customers (at the very least by failing to educate naive users). I'm sure there are some satisfied "astro" OSC uses but many come to regret that choice. And many OSC'ers don't know what they are missing or have limited ambitions for small fast scopes on large bright objects (that would do almost as well with DSLR). But this only a hobby and people should have fun – so if OSC appeals to you (even erroneously) then enjoy!
        >
        > > OSC - the QHY8 - and it has 50% QE in H-alpha.
        >
        > Actually that detector's QE is only 12.5% for H-a. 75% of the OSC pixels are completely blind to H-a (0% QE) and the remaining 25% of the pixels only detect 50% of H-a.
        >
        > 0.25 x 0.5 = 0.125
        >
        > > a good number of great H-alpha images with this OSC.
        >
        > 13% QE is in the higher range of film emulsions, which used to be the only way to take astro-photos...
        >
        > Stan
        >
      • Stan
        ... Cameras based on the nearly ubiquitous KAF-8300 are your best bet. The KAF-8300 specs are pretty good. The detector and pixel sizes (binned and unbinned)
        Message 3 of 13 , Nov 23, 2012
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          --- "Randy" <rzugnoni@...> wrote:
          > I have a Takahashi FSQ106ED...
          > also have a Celestron 11" ...
          > Is there a mono CCD that I could use that would do OK with both?

          Cameras based on the nearly ubiquitous KAF-8300 are your best bet. The KAF-8300 specs are pretty good. The detector and pixel sizes (binned and unbinned) are appropriate for a wide range of applications. There are many manufactures and models with different features and compatibilities (CFW, AO, etc.) And most of the 8300 cameras are modestly priced with good re-sale value.

          Your biggest issue will be deciding on manufacturer and model.

          Stan
        • Stan
          ... Allow me to elucidate further. In my opinion an astro camera should be specifically designed and optimized for astronomical imaging. Other cameras may
          Message 4 of 13 , Nov 23, 2012
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            --- Orlando Andico <orly.andico@...> wrote:
            > ... statement that an OSC is "malpractice"...

            Allow me to elucidate further.

            In my opinion an "astro" camera should be specifically designed and optimized for astronomical imaging. Other cameras may be utilized for taking images of astronomical objects. This is true of DSLRs and cell phones but they are not really "astro" cams. Likewise cameras designed for other purposes may be modified to improve astro imaging, such as a "modified DSLR" or the Canon 60a but these cameras are still primarily designed for other purposes and are sub-optimal for astro (e.g. the "SLR" part of a "DSLR" is useless for astro and can impact astro usage). Then there is a bastard category of cameras ostensibly designed for astro but crippled by a Bayer matrix.

            Cameras designed for astronomy have several criteria and perhaps the most important criterion is high sensitivity to a broad spectrum of light. Astro objects exhibit many spectral characteristics that are best captured unfiltered or with special filter(s). Thus the ability to use many different filters or no filter at all is a very important requirement for a true astro camera.

            OSC Bayer filters are designed to emulate human vision in terrestrial lighting conditions but many astro object spectra are very alien to such conditions. The Bayer filter matrix and response curves are inappropriate sub-optimal (even hostile) for most astro objects. For example, green is highly oversampled by the Bayer matrix (because green is the strongest color of natural sunlight and the eye is most sensitive to it) but it is one of the least interesting astro colors for pretty pix (green is useful for stellar photometry but OSC has other problems with that and very few OSC users are interesting in photometry).

            Stan
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