54542Re: [ccd-newastro] I'm about to smash my ST2k........Please stop me!
- Oct 1, 2006The 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.
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
Sent: Sunday, October 01, 2006 11:52 AM
Subject: Re: [ccd-newastro] I'm about to smash my ST2k........Please stop me!
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
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.
----- Original Message -----
From: "Photon Collector" <photoncollector@...>
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:
> It is a combination of 8, 20 minute exposures median combined after
> reduction using 10 median combined dark frames and the appropriate flat
> 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
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