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31 May 2021: APP 1.083-beta2 has been released ! APP 1.083 stable will follow soon afterwards. It includes a completely new Star Reducer Tool, New File Saver Module, Improved Comet registration and much more, check the release notes here!

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Star Colour Calibration: Magenta - Green Adjustment  

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(@mestutters)
Neutron Star Customer
Joined: 4 years ago
Posts: 128
June 9, 2021 14:07  

Hi,

Has anything been changed wrt to Magenta - Green Adjustment in the recent Beta 2 adjustment?

Looking at the below screen shot I fancy a small M-G adjustment is needed.  However the smallest available adjustment is 0.01.  The movement required would however seem to be c0.001.

Screenshot 2021 06 09 12.53.39

If I make an adjustment of -0.01 then the corection made is way over the top!  has there been a change to the sensitivity/scaling of the slider or graphical display?

Screenshot 2021 06 09 13.04.14

 

Regards

Mike


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3550
June 9, 2021 14:15  

Not that I know of, but I'll pass this one to Mabula.


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(@mabula-admin)
Universe Admin
Joined: 4 years ago
Posts: 2641
June 9, 2021 14:31  

Dear Mike @mestutters,

In 1.083-beta2 nothing has changed with regard to the star color calibration algorithms or the interface of the tool. Star detection and analysis has been improved leading to more stars being detected.

But if i look at the screenshots that you posted, I would think that you are not loading broadband data? What filters did you use to create the image?

The scales of the B-G and other axes are way too small... that is very unusual. The values should be between -1 to 1, not -0.01 to 0.01...

Please tell us as much as you can about the data, which filters did you use and how did you create the color image? I think I see that you have a LHaRGB ? If so, the Ha contribution might be killing it severly then. Best to keep narrowband out of the mix when performing star color calibration. Best would be to first create a RGB or LRGB, star color calibrate that. And then add Ha to that calibrated result 😉

Mabula

 


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(@mestutters)
Neutron Star Customer
Joined: 4 years ago
Posts: 128
June 9, 2021 17:16  

Hi Mabula,

Thanks for the very prompt response.

I must try your suggestion of producing a fully processed RGB image using broadband data alone and only then introducing NB data.  

For this target I have LRGB and Ha data all acquired using my own rig.   I have used your LHaRGB combination options (in RGB Combine) successfully in the past with this mix of filter data so not previously had cause to change my approach. For this target however I've not so far managed to produce a result that I found aesthetically pleasing.  I felt sufficiently inspired by the new beta release to have another go!

I recall that once before I've seen this issue of the graduation of the Green - Magenta adjustment being seemingly too coarse for the adjustments indicated by the graphical display but did not think to flag it up.

For this target I also have some wide-field data in OIII acquired using iTelescope that I am hoping to incorporate.  This is much wider FoV and better quality than anything I can obtain from my own backyard so altogether this may be an interesting challenge.

Regards

Mike

 


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