Leo Triplet 23 Hour LRGB

[DaveS]

Posting this for some advice. This is 15 hours RGB and 7 hr 50 Min L in 10 min subs. Sigma Add stacking with two iterations of Gradient Removal in AstroArt 7 then the RGB stacks entered into Trichromy before being given DDP. The Luminance was also given a separate DDP.

LRGB synthesis followed by a couple of rounds of Histogram Stretch, Colour Curves and Saturation Boost with sky background suppressed. A fair crop to get rid of alignment edges.

I'm trying to pull out the Tidal Tail of NGC 3628 while avoiding a horrible mottled background from some noisy data, plus avoiding burning out the cores of M 65 and M 66. so far with little success.

Comments and Criticism NEEDED, not just welcome, so please don't hang back.

[BrendanC]

I think this a great photo, beats the pants off mine.

One way to preserve the cores of galaxies is to have the original photo - or something less stretched - on a layer below, and then use a mask to expose those cores. That way you get the less blown-out core in the middle from the less stretched version, together with the fully stretched edges. It's something you can readily do in Photoshop, not sure about the packages you're using.

 

[DaveS]

Thanks Brendan.

I don't have PS, I'm doing everything in AstroArt 7 which doesn't have layers, maybe a future version. AA is a package that I've used for a while and am used to.

Time, I think to have another look at GIMP which does have layers.

[geoflewis]

Hi Dave,

I agree with Brendan that it's an excellent image, so don't be too hard on yourself. I also think that you'll probably need to use masked stretching to extract more of the tail whilst preserving the cores of M65 and M66. Ultimately though you can only push the data so far, so how clean is the background of luminance data, as that's where you'll need to push the processing to lift the tail out of the background.

Good luck.

[DaveS]

Thanks Geof.

I think I'll download GIMP again, didn't have room on my old boot drive but do now.

Will also have a closer look at my Luminance data.

[DaveS]

This is the Luminance give a brutal DDP to show the background with no concern for burning out the galaxies

[lux eterna]

This is good, but there is so much potential with layered processing using masks. I often use a workflow like @BrendanC described, I just want to add a tip: The overstretched image above is just perfect to use as a mask. If you invert this mask (galaxies are black), editing will not do much difference to the galaxies.

Ragnar

 

[geoflewis]

It looks like you have some headroom to extract more of the tail, by using an overstretched image like this (maybe somewhat less stretched) as a luminance mask to control the areas in the image that are revealed.

[DaveS]

Thanks Ragnar and Geof good tip! Something for me to get my head around, as I've not used layer masks before. Yes, I know, lazy cheapskate lol.

Edited April 27, 2020 by DaveS

[Gina]

I agree that this is a great image.  Sorry I can't suggest any improvement. 

[tooth_dr]

58 minutes ago, lux eterna said:

This is good, but there is so much potential with layered processing using masks. I often use a workflow like @BrendanC described, I just want to add a tip: The overstretched image above is just perfect to use as a mask. If you invert this mask (galaxies are black), editing will not do much difference to the galaxies.

Ragnar

 

I have been using Layer Masks routinely now, but it never occurred to use the overstretched image as the layer mask itself!  Great idea.  Do you have any links on where to learn more about this?

[DaveS]

OK, I've downloaded GIMP, but think it might be a learning curve. I've also been exploring the Masks menu in AstroArt 7, and may be able to do something there, though the "Help" and "tutorials" aren't terribly helpful here.

[Gina]

I bought AstroArt 5 some years ago but could never get the hang of it.  Then I bought a second hand tower system that had PS on it and learned to use that.  When that machine died and I bought another I bought PixInsight, which I've been using ever since.  Very powerful software and dedicated to astro processing.

[DaveS]

I did try the trial version of PI but found it difficult to get my head around its way of doing things, perhaps because I started with AA 5 and got used to its way of working. V7 is now much more powerfull than V5 and does pretty much all I want apart from layers, and now I'm looking at Masks I may be able to work around that too, especially with Ragnar's tip about using a heavily stretched image as a mask.

[Merlin66]

Yes,

AstroArt punches well above it's weight. An under-rated piece of excellent software. Fabio, the developer, has given users unlimited support over the years.

 

[lux eterna]

14 hours ago, tooth_dr said:

I have been using Layer Masks routinely now, but it never occurred to use the overstretched image as the layer mask itself!  Great idea.  Do you have any links on where to learn more about this?

I found this guide https://www.donastro.org.uk/basic-layer-masking/

This "image-as-mask" method can be used in different scenarios, one is selective stretching, another selective colour manipulation. I use it the most for selective noise reduction (targeted for the darkest areas = inverted mask ( = "ctrl-I" )). Remember that you can adjust contrast & brightness etc of the mask while you are in "mask mode" (ctrl-click on the mask thumbnail). Even a gaussian blur of the mask can be done here. You can also use a brush here to add / remove parts of the mask (but that is often better done when you are out of "mask mode").

Ragnar

[tooth_dr]

9 minutes ago, lux eterna said:

I found this guide https://www.donastro.org.uk/basic-layer-masking/

This "image-as-mask" method can be used in different scenarios, one is selective stretching, another selective colour manipulation. I use it the most for selective noise reduction (targeted for the darkest areas = inverted mask ( = "ctrl-I" )). Remember that you can adjust contrast & brightness etc of the mask while you are in "mask mode" (ctrl-click on the mask thumbnail). Even a gaussian blur of the mask can be done here. You can also use a brush here to add / remove parts of the mask (but that is often better done when you are out of "mask mode").

Ragnar

Thanks Ragnar, I’ll need to sit down and read over your message again, I understand it, just not sure where to apply it 

[lux eterna]

@tooth_dr This is an example, in "mask mode" I did Image-Adjustment-Brightness/contrast and inverted the mask (ctrl-I). This particular adjustment is "curves" but you can use the techniqe with whatever adjusment type you need.

Ragnar

[tooth_dr]

1 hour ago, lux eterna said:

@tooth_dr This is an example, in "mask mode" I did Image-Adjustment-Brightness/contrast and inverted the mask (ctrl-I). This particular adjustment is "curves" but you can use the techniqe with whatever adjusment type you need.

Ragnar

Thanks Ragnar, this is just a step ahead of where I am at the minute.  I haven't started using Adjustment Layers like that.