North America Nebula, HA or not to Ha, that's the question

[kirkster501]

FSQ85 reduced and G2-8300 with Astrodon Ha (3nm) and RGB filters.

The investment in time in the Ha image shows a nice image in itself.  However, the Astrodon red filter is so good that I am not so sure it is worth that time investment if the RGB is done 1x1.

Eight hours of 48x600s reveals this image:

...which is nice.  And when I combine it with the RGB (RGB is 360 minutes of 1x1) I get the below which is also very nice.

 

However, is the HaRGB that much different considering the vanilla RGB below considering the huge time investment in gathering that Ha?  I am not so sure.  Yes the above is a bit better, but eight hours worth better?

[vlaiv]

I prefer HaRGB version.

Imaging time brings diminishing returns. Adding one more hour of data makes huge difference if you already have just one hour of data - but makes almost no difference at all if you already have 8h of data.

Is HaRGB image going deeper? Well, yes it does - and goes deeper as you would expect from roughly doubling exposure - so everything is fine there, but did you "need" to spend that much time on target? I'm afraid - I can't answer that one.

There you go - that nebulosity is clearly more visible in HaRGB image

[Laurin Dave]

All very nice Steve,  I had a very similar experience and similar results when I did this last year.  As Vlaiv says definitely more nebulosity in the HaRGB version but that one loses the lovely pinks of the RGB..   needs some Oiii I guess to bring them back.   

[vlaiv]

2 minutes ago, Laurin Dave said:

All very nice Steve,  I had a very similar experience and similar results when I did this last year.  As Vlaiv says definitely more nebulosity in the HaRGB version but that one loses the lovely pinks of the RGB..   needs some Oiii I guess to bring them back.   

Maybe using Ha as luminance would solve that?

RGB can be binned x2 or x3 if it is only supplying chrominance data as we are far less sensitive to loss of detail in chrominance than in luminance.

Here is quick and dirty example of using Lum from Ha version on RGB only version in gimp:

[Xiga]

Very nice image Steve. I also prefer the HaRGB version, because it goes deeper, but i also like the magenta/pink hues of the plain RGB. I assume you added the Ha to the Reds only (in Blend mode Lighten, and with the stars removed), which is the more correct way of doing it, but as Vlaiv points out, adding a certain % of the Ha as Luminance will also make the reds more pink. 

Btw, if your intention is only ever to add the Ha to Red in Lighten mode, then you might be surprised just how little of it you need. 8 hrs is definitely overkill in this case, due to NAN being so bright, but even on most targets you should be able to get away with a lot less. In processing the Ha, you can actually take a sledgehammer to it and crank the contrast way up. It will look downright ugly, but because of the way it gets added, it won't really harm the resulting image. 

[Bibabutzemann]

On 06/10/2021 at 13:17, vlaiv said:

Maybe using Ha as luminance would solve that?

RGB can be binned x2 or x3 if it is only supplying chrominance data as we are far less sensitive to loss of detail in chrominance than in luminance.

Here is quick and dirty example of using Lum from Ha version on RGB only version in gimp:

Hi,

How did you manage to use the Ha Image as luminosity without altering star size?

 

Edit: oh i think i found a way myself in PS. I made the RGB image black and white and merged it in "Lighten" mode with the Ha image.

Then i used that as luminosity to get the HaRGB. Really nice and a game changer for me. Why didnt i find it sooner....

 

 

Edited October 17, 2021 by Bibabutzemann