Processing Ha-RGB images

[Pryce]

So, I've got my CLS filter and my Ha filter which I've heard is a good start. 

But my experience in processing thus far only covers RGB images. As far as I understand, Ha images are mono colored, so my question is this: how do I process my Ha and RGB images together? 

Edit: I use DSS and PS 

Edited October 23, 2020 by Pryce

[johngm]

2 hours ago, Pryce said:

So, I've got my CLS filter and my Ha filter which I've heard is a good start. 

But my experience in processing thus far only covers RGB images. As far as I understand, Ha images are mono colored, so my question is this: how do I process my Ha and RGB images together? 

Edit: I use DSS and PS 

This may be usefull

https://www.galactic-hunter.com/post/hargbcompositetutorialpixinsight

John

[Pryce]

1 hour ago, johngm said:

This may be usefull

https://www.galactic-hunter.com/post/hargbcompositetutorialpixinsight

John

Hmm,  unfortunately not much as he seems to be using different softwares than I do.  

I was hoping go continue using DSS and PS as they're softwares I'm already familiar with 

[ollypenrice]

It's quite easy and Photoshop offers my favourite way of doing it. Process your basic colour image first and save it.  Don't bust a gut trying to drag out the faintest of the red Ha signal contained in the image because you have that in your narrowband capture which you'll add later.

Next you'll need to align (AKA co-register) your Ha image so it fits over the RGB properly aligned. I dare say you can do that in DSS, I don't know. It can be done in Ps manually but it's ages since I did that. If there is any rotation between Ha and RGB that's the fiddly bit to sort out manually.

Process your Ha image as a monochrome. If you are aiming to add it to RGB you may want to process it a little differently from the way you'd do it for a standalone Ha image. Personally I push it harder if it's going into an RGB image. I go for starker contrasts and I don't worry if the darkest points are a little noisy because the dark parts won't end up in the final image.

Adding the Ha:

Select and copy (CtrlA, CtrlC) the Ha.

Open the RGB and split the channels in the channels menu.

Minimize the B and G channels with the R channel active.

Paste (CtrlV) the Ha onto the R.

In the Layers menu change the blend mode form Normal to Lighten in the drop-down. This means that the Ha influences the R only where it is brighter than the R. Where it is darker it is ignored. Before flattening the Ha onto the R check the following: Is the Ha lightening the R background? If it is you can open Levels and bring in the black point or use Curves and lower the bottom part of the curve slightly while holding up the top. Is the Ha doing as much as you'd like to make the object show? If not, use Curves, pin the bottom and lift the middle range till the Ha comes nicely into play. (If the Ha is overpowering, ignore that for a fix later on.) Flatten and Merge Channels choosing R (now modified), G and B in the right channels.

If you feel the new HaRGB has too much Ha, paste it onto the RGB in Levels and reduce its opacity till you like it.

What about Ha as luminance? Generally a bad idea because it gives pink nebulosity and bright blue star halos. It also holds down blue reflection nebulosity. However, it may be useful to paste it on top of your new HaRGB image in blend mode Luminosity at a very low opacity like 10 to 15%. Try it and see.

Some examples of this method:

https://www.astrobin.com/full/327970/0/

https://www.astrobin.com/full/301531/0/

Olly

 

Edited October 23, 2020 by ollypenrice
typo

[carastro]

A video I made on adding ha to RGB.  You may or may not need Registar as I think there is a way of lining up (registering) the Ha in DSS using the stacked RGB file as a "marker file".  I have never done it but have seen it done.

This should compliment Olly's instructions as he taught me how to combine the Ha.

Carole  

 

 

Edited October 23, 2020 by carastro

[Pryce]

Cheers guys!  This was very helpful!

[Adam1234]

Aligning the Ha to the RGB in DSS is quite easy -

1) load all the images into DSS and register,

2) Right click on the image with the highest score and select it as a reference frame, this will mean that all frames will be aligned to this

3) Stack only the RGB frames - untick the Ha leaving only the RGB ones ticked and press stack. 

4) Then stack only the Ha - there should be a button near the top to go back to the original view with your files - untick the RGB files and tick the Ha files, then click stack 

You should then end up with 2 autosave files, one for the RGB and one for the Ha and these will then be registered and aligned. 

 

Hope that helps