Hi Jase, merry Xmas to you also and all the best of health for 2009. What a stunning photo.
I thought Martin's was pretty cool but I have to admit you've topped it with flying colors. Details are amazing.
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Originally Posted by jase
Slowly getting the hang of CCDStack and its functions...nice tool, but I've got some questions from those that use it...
When you perform a heavy deconvolution, I note that CCDStack draws a border around the image (probably around 15 or so pixel from the edge of the full frame). I can understand why it does this as any image misalignment could result in erroneous data for the algorithm to calculate. Hence the reason why cropping is important when using these types of functions. But what if you've already pre-cropped the image...is there a way you can tell the function to use the entire image? I end up with a dark line (maybe 2 or 3 pixels wide) around the border of the image - how do you get around this, other than bring it into PS and use the healing brush...eeekkk!  |
Ok I can help a little bit with CCD Stack. The deconvolution tool has an algorithm that looks at the pixels around each star and it needs X pixels radius around the area it's processing. As a result it can only process a subset of your entire picture and will leave a X border because the data needed to treat the pixels it's working on doesn't exist. (as per Adam Block tutorials and some correspondence with Stan Moore.)
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Originally Posted by jase
Do you need to normalise the individual R,G,B masters before creating a colour image? (this is probably in the manual, just haven't got that far yet). I'm really struggling to get the right colours out of CCDStack. It may not appear so in this image, but let me tell you, it took me considerable amount work to get the colours to what I thought were ok. The severe glare from Alnitak didn't help. I've never had to do this level of adjustment and tweaking in MaximDL. Perhaps its normal?? Just in case you didn't know, you can renormalise over and over as many times as you want or need. Doesn't alter the data (obviously the weights can change) - this was asked at AIC.
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You do need to normalise your subs prior to run any rejection algorithm in your R, G and B stacks BUT I don't think you need to normalise the masters R,G and B prior to creating the color. To check with Stan Moore and confirm but I vaguely remember him posting somewhere that normalising the masters prior to combining the color would in fact throws your color balance. Don't quote me on this though, double check the CCDWare forums.
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Originally Posted by jase
On the RGB combine (aka Color | create menu), do you leave the saturation at 1 or lower it accordingly. I find that stars have a magenta hue to them. I'm certain the G2V colour ratio's are correct. When the saturation is lowered they disappear, but so do the other rich colour tones you've worked hard to extract. 
Sorry for all the questions, but I sense I'm not getting the maximum out of this tool.
Anyway, it was a bit of fun (correction - a nightmare) analysing and processing, but feel it came together well. All comments welcome, and last but not least, have a safe and joyful Christmas and New Year.
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Never used the saturation in CCD Stack. I save the final FIT as a 32bits float then as a scaled 16bits TIFF and do the colouring "to taste" in photoshop.