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What are the appropriate Star Color Calibration Settings for my setup (stacked data inside)

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 xiga
(@xiga)
Red Giant
Joined: 9 years ago
Posts: 34
Topic starter  

Hi Mabula 

Apologies for having to ask this, but i've viewed the video tutorials and read all the necessary threads on the forum and i'm still a bit unsure if what i'm doing is correct.

Basically, i image with an Ha-modded Nikon D5300. When i shoot RGB (i.e not NB) then i use my IDAS-D1 filter as well. It is with this filter that i am not sure of the star color calibration settings to use. I am never sure when i have reached the desired end-point.

I have included a link below to some recent data i took. It is about 7 hrs worth of 5 and 6 min subs, all dithered. So even though the equipment used was not expensive, it should sull be pretty good data to work with. 

I know you're a busy guy and all, but if you could spare a few minutes to test out the data and post a few pictures of the settings you think are appropriate, along with the logic behind them, it would be a huge help to me. 

Best Regards,

Ciarán. 

https://1drv.ms/u/s!AhhWC3D3zU7Bnxj5rl-2RKsLtnXs



   
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(@Anonymous 174)
Joined: 9 years ago
Posts: 5702
 

Let me have a go with it, he indeed is very busy at the moment. 😉 I'm downloading it and will have a look.



   
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(@gregwrca)
Black Hole
Joined: 9 years ago
Posts: 228
 

Star color calibration is kind of confusing and almost always ends up being worse for me



   
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 xiga
(@xiga)
Red Giant
Joined: 9 years ago
Posts: 34
Topic starter  

Thanks Vincent!

Let me know how you get on  👍 



   
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(@mestutters)
Neutron Star
Joined: 9 years ago
Posts: 175
 

Hi Xiga,

I hope you won't think me presumptious but I've taken the liberty of downloading your data to see what I could achieve and maybe also improve my own processing skills.

The result I achieved is as follows:

St avg 25205.0s LNMWC 1 3.0 none x 1.0 LZ3 NS full qua add sc BWMV nor AAD RL noMBB 4thLNC it1 mod lpc cbg csc SC St

I hope you think this is reasonably decent though I fancy there is maybe still a slight green cast.

The steps I used were as follows:

1.  Batch modify, to remove the effects of frame rotation during image capture

2.  Remove LPC

3.  Calibrate Star Colours, the settings I used here are shown in the attached screen-shot.

Screenshot 2018 10 31 19.32.13

:  I found that the image was very sensitive to single steps changes on the Blue - Red slider at the -0.10 -  -0.11 setting.

4.  HSL selective colour - followed the steps in Part 6 of Mabula's Mosaic Tutorial Milky Way to Rho Ophiuchi but omitting step 3 and adding an extra step to slightly desaturate the blueness in the stars.

5.  Final adjustments to the Image Viewer setting at the RHS followed by save as JPG.

 

Hope this is a some value to you.  I enjoyed the practice at least.

Best Regards

Mike

 



   
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(@mestutters)
Neutron Star
Joined: 9 years ago
Posts: 175
 

Hi,

Just to follow up my comment about a Green cast in the above image,  here is a version saved with slightly increased saturation after application of the Photoshop HLVG plug-in.  I think it is a marked improvement.

Mike

St avg 25205.0s LNMWC 1 3.0 none x 1.0 LZ3 NS full qua add sc BWMV nor AAD RL noMBB 4thLNC it1 mod lpc cbg csc SC St v05

 



   
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 xiga
(@xiga)
Red Giant
Joined: 9 years ago
Posts: 34
Topic starter  
Posted by: mestutters

Hi Xiga,

I hope you won't think me presumptious but I've taken the liberty of downloading your data to see what I could achieve and maybe also improve my own processing skills.

The result I achieved is as follows:

St avg 25205.0s LNMWC 1 3.0 none x 1.0 LZ3 NS full qua add sc BWMV nor AAD RL noMBB 4thLNC it1 mod lpc cbg csc SC St

I hope you think this is reasonably decent though I fancy there is maybe still a slight green cast.

The steps I used were as follows:

1.  Batch modify, to remove the effects of frame rotation during image capture

2.  Remove LPC

3.  Calibrate Star Colours, the settings I used here are shown in the attached screen-shot.

Screenshot 2018 10 31 19.32.13

:  I found that the image was very sensitive to single steps changes on the Blue - Red slider at the -0.10 -  -0.11 setting.

4.  HSL selective colour - followed the steps in Part 6 of Mabula's Mosaic Tutorial Milky Way to Rho Ophiuchi but omitting step 3 and adding an extra step to slightly desaturate the blueness in the stars.

5.  Final adjustments to the Image Viewer setting at the RHS followed by save as JPG.

 

Hope this is a some value to you.  I enjoyed the practice at least.

Best Regards

Mike

 

Hi Mike

Of course i've no problem with you downloading the data to practice on 🙂 

Thanks for having a go - i'm not sure though if i agree with your settings (although i'd like some expert input to be sure). It was my understanding that you should change both slopes by an equal percentage, and it looks like you changed the top slope much more than the bottom one. I'm also not sure if moving the Blue-Red slider towards Blue is correct. It looks to me like this leads to more blue stars than red, and i though it was supposed to be the other way around. In terms of the constants, i can't recall what i used myself, although i have a gut feeling they were much lower than yours (probably somewhere between -0.1 and -0.25 but i'm just guesstimating now!). 



   
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 xiga
(@xiga)
Red Giant
Joined: 9 years ago
Posts: 34
Topic starter  
Posted by: mestutters

Hi,

Just to follow up my comment about a Green cast in the above image,  here is a version saved with slightly increased saturation after application of the Photoshop HLVG plug-in.  I think it is a marked improvement.

Mike

St avg 25205.0s LNMWC 1 3.0 none x 1.0 LZ3 NS full qua add sc BWMV nor AAD RL noMBB 4thLNC it1 mod lpc cbg csc SC St v05

 

Hi Mike. I agree with you, the first one had too much Green. The 2nd version is much better, although for me personally, i still find it a bit too green as well (but that could just be me!).

I suppose i should attach my final processed version as well. You can see it below. For this version, i had to use a stack that had no Star Color Calibration routine ran on it. Only then was i able to naturally (i.e without playing any funny business with the colors, such as with selective color adjustments) come to a version with the colors of the one below, which i personally really liked. For some reason, if i tried using Star Color Calibration, i could never reach this color balance later in processing. It just always looked off to me. So i figured i wasn't using the right settings, which is why i would like an experienced user of this tool to give it a whirl so i will know in future exactly what settings to use. 

M31 (new) v1


   
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 xiga
(@xiga)
Red Giant
Joined: 9 years ago
Posts: 34
Topic starter  
Posted by: Vincent Groenewold - Moderator

Let me have a go with it, he indeed is very busy at the moment. 😉 I'm downloading it and will have a look.

Hi Vincent

Did you have any luck with the Star Color Calibration on my data?  



   
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(@mestutters)
Neutron Star
Joined: 9 years ago
Posts: 175
 

Hi Xiga,

I cannot say that I am expert in APP but my understanding of what Mabula has said in his video tutorials and Forum posts is the Magenta - Green sliders should be adjusted by approximately equal amounts.  I believe the function of the slope sliders is to adjust the slope of the  green chart line to best match the slope of the star populations as shown by the colour - colour charts.   I agree that the purpose of the Red - Blue slider is to suitably balance the populations of Red and Blue stars and in this regard I was looking to achieve a slightly higher population of Red to Blue that I actually managed in your image but having said that many images that I see on eg Astrobin do not achieve this objective either.  Maybe with some more fine tuning of the parameters a better result could be achieved.  In any case I do not think you will find a set of CSC values that will apply equally to all images that you take with the same imaging set-up. Each image needs to be adjusted on its merits though I agree it is useful to have an idea of the starting values that are likely to achieve success.

I will be interested to hear if Mabula has a view on the best order to approach the parameter settings.  From my experience the available parameters are not completely independent variables so by changing one setting it is often necessary to make a subsequent change elsewhere.

At this stage I don't think there is a completely objective way to approach this.  I think you need to achieve a result that ultimately is pleasing to you and in this regard I try to get a result that approximates as best that I can get to (in my case LRGB) images that have achieved APOD or similar distinctions elsewhere.

Anyway have fun on your journey to astroimaging nirvana.

Regards

Mike



   
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(@Anonymous 174)
Joined: 9 years ago
Posts: 5702
 

Hi @xiga, my apologies for not coming back to you a bit sooner, by sheer coincidence both me and Mabula had super busy weeks.

Yes I did have a go at your data and to be honest, my experience with adjusting color is still a bit limited in APP as my routine has always been to do that in PI. 😉 But, I had the exact same result as Mike, couldn't get the saturation up to my liking and with a bit of a green cast after calibration. Indeed, without using that it looks a bit more like what you would expect. The routine is constantly being addressed and improved as can be seen in the latest 1.069. Could you check if that gives a slightly better result?



   
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