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54555Re: I'm about to smash my ST2k........Please stop me!

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  • rhtrembl
    Oct 1, 2006
      In order to help you on this problem,
      I conducted a number of test today:
      I took a series of 20 dark frame on a ST8E parallel port
      on a compaq presario. I got some random noise but the amplitude
      was fairly the same on 5 dark frames. say average noise is 120.
      I got peak at 320.
      I then conducted similar test with my st10xme using ubs interface.
      I then got peak at 1300 wich is 10fold that of the st8e.
      all this has been done at -10C.
      Any other st8E or st10xme with the same results?
      p.s. My st8 has just been overhaul a month ago at sbig where they
      replaced the interface board.
      Hope this help.

      --- In ccd-newastro@yahoogroups.com, "Photon Collector"
      <photoncollector@...> wrote:
      > People, I'm at wit's end.
      > I have been imaging with my ST2k imager for a couple years now. I
      have always had big problems with random hot (or bright) pixels. My
      images and darks have the usual consistent hot pixels that subtract
      out as they should. But both the images and the darks also have a
      large quantity of random hot pixels that differ from image to image
      and dark to dark. These random hot pixels do not subtract out
      because they pop up at random throughout the images and darks. The
      result is an image with many bright and dark pixels. Bright pixels
      remain in the image because the dark frame doesn't contain a
      corresponding bright pixel to subtract out. Dark pixels appear in
      the reduced image because the dark frame has bright pixels where
      there are none on the image.
      > To prove to myself that the problem is real, I subtracted one dark
      frame from another dark frame shot in sequence. The resultant image
      should be very smooth. Instead it has bright and dark pixels, just
      like my images. As another test, I shot 10 darks in a row, of course
      all with the same temp and time settings. Then I opened them up in
      both Maxim and CCDSoft and ran a blink comparison. During the blink
      comparison, you can see that about 1/2 of the hot pixels are fixed
      in their position while the rest jump around all over the image. The
      same is true when doing a blink comparison of a series of raw images
      shot in sequence.
      > I even went as far as upgrading my imaging chip from the older
      2001 chip to the new and (supposedly) less noisy 2020 chip at great
      cost to me. The results are exactly the same.
      > Here is an example of a completed image:
      > It is a combination of 8, 20 minute exposures median combined
      after reduction using 10 median combined dark frames and the
      appropriate flat fields.
      > If someone out there has a broadband connection (12 meg file!) and
      is willing to help, I have up-loaded a zip file containing a raw
      image, a flat field, and 3 dark frames. Try processing the image
      with the data I provided to see if you can get a clean image......I
      sure can't. Here is the zip file with everything you need:
      > In the past I would spend an hour or two with the clone tool
      cleaning up every bad pixel. But I just can't believe this is what
      everyone else goes through. I never hear about problems similar to
      what I'm having. I hope it's just something I'm doing wrong but I
      can't imagine what it is. Is it possible that something in the
      observatory environment is causing the random hot pixels?
      > ---Frank Rocketman Uroda
      > [Non-text portions of this message have been removed]
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