Re: M17 - Swan Emission Nebula (HaRGB)

Anthony Ayiomamitis <anthony@...>

Hi Dennis,

I agree with you fully that there is much more detail (and contrast) in the Ha standalone versions and it is for this reason that I provided both an HaRGB and Ha version for M17 at and, in fact, the same will be the case for work in progress involving M8 - - and the Crescent Nebula - - where the Ha has already been acquired and the RGB data is waiting processing (M8) or is outstanding (Crescent Nebula).

There were multiple luminance layering efforts so as to bring in as much of the Ha as possible but it was diluting my result too much and I was stuck with the infanous salmon look with my final results. In fact, this particular example is strictly (Ha-R)GB.

After posting my message last night, I did stretch the final result further and I can get further dim nebulosity in the periphery relatively easily. It also dilutes the dominant reddish colouration and trends towards the orangish flavour that Stuart describes. I will sit down today and play with the result further.


O/H dennis_persyk έγραψε:

Hi Anthony,

Thanks for sharing the beautiful images and artfully prepared web presentation. I am particularly interested in comparing your HaRGB to my straight and colorized Ha's: <>

I have been taking an informal poll on which one viewers prefer and the B&W wins by a large margin. The respondents say they can see more structure in the plain B&W. I blame this on the colorizing algorithm which clips and sets the black point too far towards zero.

But in your HaRGB I can also see more structure in the Ha luminance. This is especially true at the far right edge and elsewhere in regions of faint luminosity. What do you think?

Clear skies,

Dennis Persyk
Igloo (Now Roll-Off) Observatory Home Page <>
Hampshire, IL
Pier Design <>

--- In ap-gto@... <>, Anthony Ayiomamitis <anthony@...> wrote:


I just finished processing my data from last night involving M17 in

I had very good seeing but the transparency was volatile with thin
clouds coming and going. This is a bright emission nebula and one
can get good signal with relatively little total exposure time. For a result based on 160 minutes total data (HaRGB @ 70:30:30:30), please see .

Comments and criticism most welcome .... oh yeah, I sinned yet again
(vis a vis no spikes).


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