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Originally Posted by PhotonCollector
Why is the green interesting ? (here's some info about the colours of the Helix I have at hand; look at this AAO Image http://www.aao.gov.au/images/captions/aat015.html it says: "The greenish middle portion is evidence of excited oxygen atoms...." ) |
OK. It's just that when I did my helix with my 300D, that colour turned out much bluer than yours: (I think you are right about the red noise)
http://users.bigpond.net.au/itchysas...30finalweb.jpg
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By sub-frames do you mean individual exposures ? Thinking that you do, then the answer is yes (otherwise it would not be green in the final image).
However it is certainly my processing which effected the stronger colours.
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Yes, "subframes" refer to your original individual exposures.
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Do you process 'n stack your images by hand ? or do you have some software that does it for you ?
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I use ImagePlus to do the basic processing. I shoot in RAW and convert to pre bayer CFA (Colour Filter Array). IP does the calibration (darks, flats and bias) including an auto matched dark. I then covert the CFA frames to colour before I align and stack. IP gives a range of stacking options. With a large number of subframes the sigma average seems to work really well. Once stacked I use IP's digital development process to do the initial stretch and then move to Photoshop to do the levels & curves, etc.
One thing that I have noticed is that ImagesPlus seems to enhance the blue in an image a little more that my manual attempts, so perhaps that is a factor in my centre of the helix being so blue.
Cheers