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54542Re: [ccd-newastro] I'm about to smash my ST2k........Please stop me!

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  • Photon Collector
    Oct 1, 2006
      The hot and cold pixel removal tools in MaxIM didn't do much at all. Instead I used the median kernel filter in MaxIM on each of my subframe right after initial reduction. I then did a median combine of the 8 subframes.
      The image is MUCH better! Take a look but please excuse my quick post-processing. Nothing was done to remove bad pixels in PS.
      http://publicmissiles.com/franku/2020_-25_f55_processed2_NGC_7331.jpg

      Of course, this is not a fix of the root cause but it's many times better than ever before. I'm still running my equipment tests.

      ---Frank Rocketman Uroda


      ----- Original Message -----
      From: Bert Katzung
      To: ccd-newastro@yahoogroups.com
      Sent: Sunday, October 01, 2006 11:52 AM
      Subject: Re: [ccd-newastro] I'm about to smash my ST2k........Please stop me!


      Hi Frank:
      I've had that sort of salt & pepper artifact problem on occasion with my
      ST10-XME; don't know what causes it or cures it, seems to have its own
      schedule.
      On the positive side, I find I can get rid of them with the hot and cold
      pixel removal tools in MaxIm. Extra steps, but they clean up pretty
      well---never have to use the clone tool in Photoshop.
      Bert

      katzung1@...
      www.astronomy-images.com
      www.visionlightgallery.com/katzung/

      ----- Original Message -----
      From: "Photon Collector" <photoncollector@...>
      To: <ccd-newastro@yahoogroups.com>
      Sent: Saturday, September 30, 2006 11:13 PM
      Subject: [ccd-newastro] I'm about to smash my ST2k........Please stop me!

      > 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:
      > http://publicmissiles.com/franku/2020_-25_f55_processed_NGC_7331.jpg
      > 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:
      > http://publicmissiles.com/franku/Raw_stuff.zip
      > 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
      >





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