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[Solved] Problem with Multi Channel / Session stack  

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(@skanker)
Red Giant Customer
Joined: 3 years ago
Posts: 76
March 13, 2021 10:46  

Hello from Austria!

On 6 evenings I collected 3 sessions of RGB data and 3 sessions of Halpha data (Canon 6Da, Sigma 105mm f1.4 A & almost same framing).

I stacked the channels separately and then wanted to fade in the H-alpha image into the RGB image. Unfortunately, the two images are not congruent because the H-alpha image is quite distorted in the middle (check the pics).

Orion RGB
Orion halpha
blend

 

Next try:

I have now loaded all channels and sessions into APP and registered all images on the RGB image with the best quality value (DDC & "same camera + optics" activated)

RMS value RGB: 0.15 - 0.22
RMS value H-alpha: 0.4 - 0.5

I think that still doesn't fit perfectly. What else could I try?

CS Gernot


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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1110
March 14, 2021 01:45  

@skanker I am sorry but I am not quite sure what you are trying to explain about the distortion of the Ha images. The Ha image that you posted looks great to me and if I compare it to the colour one then it seems to be OK. I *think* that you may want to indicate the issues with the arrows in the third but I really don't understand what you are trying to explain there. Can you please explain in a more verbose way?

When you write that registering and integrating all images "still doesn't fit perfectly", what does that mean? Can you post an image explaining what is wrong and again be as verbose as you can?

Thanks, Wouter


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(@skanker)
Red Giant Customer
Joined: 3 years ago
Posts: 76
March 14, 2021 08:57  

Hi Wouter! @wvreeven

I will try again to explain the problem 🙂

I stacked the RGB and the Halpha data separately from each other. The next step was to edit the stacks in Photoshop. When I wanted to fade in the Halpha stack into the RGB stack, I noticed that the nebula structures did not fit on top of each other. In the third picture you can see the Halpha layer (with 50% opacity) over the RGB layer.

As you can see, the structures on the right don't fit on top of each other!

You can download the first two pics and try to align them in Photoshop.I think then you will notice what I mean.

I also tried to register the Halpha lights on the finished RGB stack. After stacking them I got the the same bad result. 

 

Thanks for your help 🙂

Gernot

 

 


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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1110
March 14, 2021 15:15  

@skanker Hi Gernot,

OK now I understand. After integrating the RGB and H-Alpha images separately, you can register the two integration results by loading them as lights in tab 1 without loading the calibration frames. Then go to tab 4 and register them. After registering you can save the registered frames in tab 4 and then you can try to combine them.

I can try to help you with that but then I would prefer to do that with the original stacks because the JPEG images that you put in your post are of poorer quality than the original FITS files. Please try to register them first yourself and see if that solves your issue. If not, let me know here and I'll help you upload your files to our file server so I can have a look.

EDIT: By the way, it looks like you removed all stars from the images. Are you sure that at least part of the artefacts are not caused by that? Stars are much brighter in RGB than in Ha and even the best star removal tools leave traces.

 

Thanks, Wouter


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(@skanker)
Red Giant Customer
Joined: 3 years ago
Posts: 76
March 14, 2021 21:57  
Posted by: @wvreeven

@skanker Hi Gernot,

OK now I understand. After integrating the RGB and H-Alpha images separately, you can register the two integration results by loading them as lights in tab 1 without loading the calibration frames. Then go to tab 4 and register them. After registering you can save the registered frames in tab 4 and then you can try to combine them.

I can try to help you with that but then I would prefer to do that with the original stacks because the JPEG images that you put in your post are of poorer quality than the original FITS files. Please try to register them first yourself and see if that solves your issue. If not, let me know here and I'll help you upload your files to our file server so I can have a look.

EDIT: By the way, it looks like you removed all stars from the images. Are you sure that at least part of the artefacts are not caused by that? Stars are much brighter in RGB than in Ha and even the best star removal tools leave traces.

 

Thanks, Wouter

I will try it!

Greets Gernot


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(@skanker)
Red Giant Customer
Joined: 3 years ago
Posts: 76
March 27, 2021 14:34  

@wvreeven

Hello Wouter!

I was able to solve the problem.

I reloaded the lights and registered them to the best quality RGB-light. After the stacking process, the RGB and Halpha data were congruent and had no distortion.

I spoke to a specialist who said that such short focal lengths often lead to such problems because of the curvature of the field.

In any case, it wasn't a problem from APP. The source of the error is usually in front of the computer 🙂

I posted the finished project into the gallery section.

Thanks for the help and greetings from Austria!

 

Gernot 


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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1110
March 27, 2021 14:38  

@skanker Hi Gernot, good to know that you were able to solve the issue. Greetings from Chile!


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