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Galaxy Ha enhancement strategy

Andre Vilhena
in PixInsight
Hello,

I've just seen M51 continuum subtraction (CS) video and I am wondering which strategy could be used when we have an LRGB image. I haven't tried yet but if we do the enhancement in linear image before LRGB combination, I would expect the lightness combination to reduce the enhancement done on the RGB - am I correct?
If yes, what could be a strategy to handle that? Could it be:

1) Do the enhancement also to L before doing LRGB combination? (my bets are on this one)
2) Do LRGB combination before stretching? (never seen this)
3) Do the enhancement in an already stretched LRGB image? (would CS work the same way? Maybe not)

Thanks,
André

Comments

  • BlockHeadBlockHead
    Andre,

    Did you notice this is an LRGB image? (maybe you did not watch from the beginning?)
    At the moment, I am arguing that it is enough to enhance the Ha in the Red channel alone. I believe the Hii regions are already represented well with contrast in the L image- they do not need more signal added to them in L- we just need to color them. 

    If the object has an Ha component in the color image that is no represented in the Luminance (like a faint nebula)- then yes, you need to add Ha to the color Luminance. 

    The addition of the information could be done in either the linear stage (such as I did) or the linear stage- depending on how much control is required to get the signal into the data. In the case that one of the signals is very weak- then a non-linear image with screen is likely the best answer.

    -the Blockhead
  • Andre Vilhena
    Hi Adam,

    Now I feel ashamed... Indeed I did not watch from the beginning and skipped directly to Ha enhancement...
    :-S  I saw it was done in linear stage and assumed it was only RGB. 

    Lesson learned and will see it from the beginning.

    Cheers,
    André
  • Andre Vilhena
    Hi,

    Lesson learned and I think I did quite well... :)

    Cheers,
    Andre
    M31_core.jpg
    3045 x 2055 - 5M
  • BlockHeadBlockHead
    Excellent.
    -the Blockhead
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