54543Re: [ccd-newastro] I'm about to smash my ST2k........Please stop me!
- Oct 1, 2006I can't speak to the cause of your problem, although I think Terry's
idea about CPU cycles possible being an issue is worth examination.
When was the last time you updated your SBIG drivers? Older versions of
the SBIG drivers, when loaded into your camera, would cause you to get
How sure are you of the voltage going into the camera? If available, try
an alternate power supply.
From a processing angle, download Russell Croman's RC-Astro Console for
MaxIm DL. It contains a routine for identifying and dealing with random
pixel variations. I used it with my STL-11000 before SBIG provided new
drivers that eliminated the random pixel problem (well, mostly). To
Your long exposures are also potentially an issue, especially if this is
related to power supply fluctuations. What kind of variations do you get
with 5- or 10-minute images/darks?
Also, just a point: if you are going to take eight images, then take at
least 8 darks. Otherwise, your darks are adding more noise than they
should to the final result.
As others have suggested, the ABG chips in the SBIG cameras perform
noticeably better if you dither across several pixels. This alone can
make a significant difference by offsetting the pixels and allowing
rejection algorithms to function more effectively.
Photon Collector wrote:
> 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.
> 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: firstname.lastname@example.org
> 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
> 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@...>
> To: <email@example.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
> [Non-text portions of this message have been removed]
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