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ASTRO: Holmes on the 18th UT reprocessed
After seeing what a hard unsharp mask did to Homes in another post here
I went back and tried a moderate one to my 18th image. I hate panda eyes so stopped before they showed up on the dimmer stars though the core and a few brighter stars show a mild form of the "disease". It did though help bring out the streamers in the inner regions. Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
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ASTRO: Holmes on the 18th UT reprocessed
Rick Johnson wrote: After seeing what a hard unsharp mask did to Homes in another post here I went back and tried a moderate one to my 18th image. I hate panda eyes so stopped before they showed up on the dimmer stars though the core and a few brighter stars show a mild form of the "disease". It did though help bring out the streamers in the inner regions. Rick Rick I have done some processing of this and yours above. I hope this is OK. Jerry Warner -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". ------------------------------------------------------------------------ [Image] |
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ASTRO: Holmes on the 18th UT reprocessed
more
Jerry Rick Johnson wrote: After seeing what a hard unsharp mask did to Homes in another post here I went back and tried a moderate one to my 18th image. I hate panda eyes so stopped before they showed up on the dimmer stars though the core and a few brighter stars show a mild form of the "disease". It did though help bring out the streamers in the inner regions. Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". ------------------------------------------------------------------------ [Image] |
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ASTRO: Holmes on the 18th UT reprocessed
Working from JPG images tends to result in just enhancing the artifacts
of JPG compression. This is why you see all the point like sources in the middle of the three images in this series. Also the FITs image contains a brightness range of 100 to 62000 ADU counts. Only 256 of those fit in a JPG image so most of the data has been thrown away before you even get started. But its the JPG artifacts that really can lead the processing down the wrong path. Also it is best to remove the color data before doing any processing as that too contains artifacts adding to the problem. Given the tremendous amount of data in a FITS image compared to what a computer screen can display you can play this enhancement game for years and never see it the same way twice. When pushing even FITS data hard you have to look out for artifacts forming. They are inevitable and you just have to live with them and recognize which features are real and which are artifacts. For instance when doing a heavy unsharp mask you will get ringing around a bright edge. But only on one side. Since a bright star has only one edge (the outside) you get an intense darkening surrounding the star often called Panda Eyes. But with the bow shock of this comet being in an arc as shown in another posting here you get a darkening mostly on the side of highest contrast, again the outside so you see a strong black arc you labeled as a void in that picture. It's just the type of Panda Eye you get from such a feature. Without seeing the original data I can't tell but suspect that many other of the voids are due to the mathematics of unsharp masking as well. Some may be real. Only looking at the original unprocessed data can you tell which is which. For the attached image I worked hard to give a strong unsharp mask but still prevent these types of artifacts from developing. This takes many many steps and takes me several hours of very slow progress. After running for about 10 hours the attached is the result. The graininess in the bright areas is mostly noise and not real -- I think. As I slept through most of it and didn't watch its progress I can't say for sure but with only 4 minutes of data noise seems the likely explanation. The routines are applied with varying intensity depending on the signal strength. It appears I applied them too weakly to faint signals and too strongly to bright ones as the faint areas are too smooth and the bright too rough. But I don't feel like spending another ten hours trying a different curve so this will have to do. No matter how I processed the FITS image I saw no sign of those point sources in the middle of your last set of three images. I think they were the result of how your processing handled the noise and JPG artifacts. Back in the 70's I designed digital math circuits for processing audio data for high speed teletype experiments the FCC let me and a few other hams run. I had to develop math routines to deal with just this type of artifact though in audio we called it "ringing" but in visual image processing you see the "ringing" as Panda Eyes and other artifacts. The bright rings around stars from deconvolution is another form of it for instance. So I used routines to develop my own filters that I used on this attached image to get a lot of unsharp masking with little ringing. They work just fine visually as well as with audio but really tax even today's computers compared to what was needed for the same at audio frequencies. There, before even the earliest 4 bit processors, I used TTL gates to do the processing in real time. Rick warner wrote: more Jerry |
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ASTRO: Holmes on the 18th UT reprocessed
Rick Johnson wrote: Working from JPG images tends to result in just enhancing the artifacts of JPG compression. This is why you see all the point like sources in the middle of the three images in this series. Also the FITs image contains a brightness range of 100 to 62000 ADU counts. Only 256 of those fit in a JPG image so most of the data has been thrown away before you even get started. But its the JPG artifacts that really can lead the processing down the wrong path. Also it is best to remove the color data before doing any processing as that too contains artifacts adding to the problem. Given the tremendous amount of data in a FITS image compared to what a computer screen can display you can play this enhancement game for years and never see it the same way twice. When pushing even FITS data hard you have to look out for artifacts forming. They are inevitable and you just have to live with them and recognize which features are real and which are artifacts. For instance when doing a heavy unsharp mask you will get ringing around a bright edge. But only on one side. Since a bright star has only one edge (the outside) you get an intense darkening surrounding the star often called Panda Eyes. But with the bow shock of this comet being in an arc as shown in another posting here you get a darkening mostly on the side of highest contrast, again the outside so you see a strong black arc you labeled as a void in that picture. It's just the type of Panda Eye you get from such a feature. Without seeing the original data I can't tell but suspect that many other of the voids are due to the mathematics of unsharp masking as well. Some may be real. Only looking at the original unprocessed data can you tell which is which. For the attached image I worked hard to give a strong unsharp mask but still prevent these types of artifacts from developing. This takes many many steps and takes me several hours of very slow progress. After running for about 10 hours the attached is the result. The graininess in the bright areas is mostly noise and not real -- I think. As I slept through most of it and didn't watch its progress I can't say for sure but with only 4 minutes of data noise seems the likely explanation. The routines are applied with varying intensity depending on the signal strength. It appears I applied them too weakly to faint signals and too strongly to bright ones as the faint areas are too smooth and the bright too rough. But I don't feel like spending another ten hours trying a different curve so this will have to do. No matter how I processed the FITS image I saw no sign of those point sources in the middle of your last set of three images. I think they were the result of how your processing handled the noise and JPG artifacts. Back in the 70's I designed digital math circuits for processing audio data for high speed teletype experiments the FCC let me and a few other hams run. I had to develop math routines to deal with just this type of artifact though in audio we called it "ringing" but in visual image processing you see the "ringing" as Panda Eyes and other artifacts. The bright rings around stars from deconvolution is another form of it for instance. So I used routines to develop my own filters that I used on this attached image to get a lot of unsharp masking with little ringing. They work just fine visually as well as with audio but really tax even today's computers compared to what was needed for the same at audio frequencies. There, before even the earliest 4 bit processors, I used TTL gates to do the processing in real time. Rick Rick I very much appreciate your comments here. A real education one could get nowhere else. Frankly, I a not surprised at anything you say; just the explication of it which it would take hours to find elsewhere. This helps tremendously. Very sincerely, Jerry Warner warner wrote: more Jerry ------------------------------------------------------------------------ [Image] |
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ASTRO: Holmes on the 18th UT reprocessed
Rick - I like this core image, best I've saw among the many post of Holmes both hear and on other list. Thu, 22 Nov 2007 13:07:32 -0600, Rick Johnson wrote: Working from JPG images tends to result in just enhancing the artifacts of JPG compression. This is why you see all the point like sources in the middle of the three images in this series. Also the FITs image contains a brightness range of 100 to 62000 ADU counts. Only 256 of those fit in a JPG image so most of the data has been thrown away before you even get started. But its the JPG artifacts that really can lead the processing down the wrong path. Also it is best to remove the color data before doing any processing as that too contains artifacts adding to the problem. Given the tremendous amount of data in a FITS image compared to what a computer screen can display you can play this enhancement game for years and never see it the same way twice. When pushing even FITS data hard you have to look out for artifacts forming. They are inevitable and you just have to live with them and recognize which features are real and which are artifacts. For instance when doing a heavy unsharp mask you will get ringing around a bright edge. But only on one side. Since a bright star has only one edge (the outside) you get an intense darkening surrounding the star often called Panda Eyes. But with the bow shock of this comet being in an arc as shown in another posting here you get a darkening mostly on the side of highest contrast, again the outside so you see a strong black arc you labeled as a void in that picture. It's just the type of Panda Eye you get from such a feature. Without seeing the original data I can't tell but suspect that many other of the voids are due to the mathematics of unsharp masking as well. Some may be real. Only looking at the original unprocessed data can you tell which is which. For the attached image I worked hard to give a strong unsharp mask but still prevent these types of artifacts from developing. This takes many many steps and takes me several hours of very slow progress. After running for about 10 hours the attached is the result. The graininess in the bright areas is mostly noise and not real -- I think. As I slept through most of it and didn't watch its progress I can't say for sure but with only 4 minutes of data noise seems the likely explanation. The routines are applied with varying intensity depending on the signal strength. It appears I applied them too weakly to faint signals and too strongly to bright ones as the faint areas are too smooth and the bright too rough. But I don't feel like spending another ten hours trying a different curve so this will have to do. No matter how I processed the FITS image I saw no sign of those point sources in the middle of your last set of three images. I think they were the result of how your processing handled the noise and JPG artifacts. Back in the 70's I designed digital math circuits for processing audio data for high speed teletype experiments the FCC let me and a few other hams run. I had to develop math routines to deal with just this type of artifact though in audio we called it "ringing" but in visual image processing you see the "ringing" as Panda Eyes and other artifacts. The bright rings around stars from deconvolution is another form of it for instance. So I used routines to develop my own filters that I used on this attached image to get a lot of unsharp masking with little ringing. They work just fine visually as well as with audio but really tax even today's computers compared to what was needed for the same at audio frequencies. There, before even the earliest 4 bit processors, I used TTL gates to do the processing in real time. Rick warner wrote: more Jerry |
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ASTRO: Holmes on the 18th UT reprocessed
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ASTRO: Holmes on the 18th UT reprocessed
......and found a cat hair across the luminosity filter......
Rick, Now that's a new one....... I've heard of guys complaining about cat footprints running across the primary of their big Dobs....... George N |
#9
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ASTRO: Holmes on the 18th UT reprocessed
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#10
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ASTRO: Holmes on the 18th UT reprocessed
Rick, detail is quite like my images with Larson-Sekanina filter, only
without the ugly artifacts that this filter gives. I have not been able to extract similar detail with unsharp masking. Stefan "Rick Johnson" schrieb im Newsbeitrag ... After seeing what a hard unsharp mask did to Homes in another post here I went back and tried a moderate one to my 18th image. I hate panda eyes so stopped before they showed up on the dimmer stars though the core and a few brighter stars show a mild form of the "disease". It did though help bring out the streamers in the inner regions. Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
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