Star Color Calibration Issue

Maybe you have a dark frame problem like me although your results don't look so bad - mine appeared to lose all red content. If things don't go as expected, analyze your darks, flats and bias frames. Do an integration with only the lights and then successively do more integrations while adding one of the calibration frame types each time. Good luck

@astrogee

Thanks for the reply mate ...

My calibration frames are from my library and are check it ...

I still cant understand why the star color calibration effects on galaxy or in nebulosity ...

Normal must effect only in star color ...

If you want i can upload my files to give a try ...  

Hi Stratos, My understanding was that the star colour calibration was using stars to calibrate the white balance of the whole image. Your image looks like its not lacking in colour - maybe too much. Do you have a UV/IR cut filter? Without one you will get too much red from the IR spectrum above Ha.

@astrogee

My R G B data is from L pro filter that have uv-ir cut ...

my Ha data is extract from L enhance  filter so must not be a problem...

Is this your first time with those filters? I think some of them can affect the normal colour so maybe you should not do star colour calibration. Narrow band imaging will not give you true colour - although I think the L-Pro is pretty balanced, but not L-enhance. You kind of have to mix and match the colours to give something nice looking like the Hubble palette. I think you can skip star colour calibration.

Actually, I think you need to do multichannel/filter processing and then do combine RGB Tool at the end.

@astrogee

Its not first time that i using these filters ... I shoot almost exclusively with them ... from L enhance I took only ha so can’t unbalance my rgb ...

@astrogee I Use this workflow my friend for this kind of data ...

https://www.astropixelprocessor.com/community/tutorials-workflows/combining-r-g-b-with-ha-oiii-data-using-an-optolong-l-enhance-filter/

Posted by: @hyperion

@astrogee I Use this workflow my friend for this kind of data ...

https://www.astropixelprocessor.com/community/tutorials-workflows/combining-r-g-b-with-ha-oiii-data-using-an-optolong-l-enhance-filter/

That looks awfully complicated. I think APP will do it all with multichannel processing by adding each RGB and Ha-OII - tab 0 has Ha-OIII algorithm, which I think you can add to the RGB with RGB tools at the end. I've done narrow band but not OSC narrow band, which I think has been supported very recently, since that posting.

@astrogee

We will wait to see what moderators will answer mate ... I’m very interesting too see how will work the star color calibration...or if I must skip it ...

It's not too complicated when you follow along. APP can't normalize mono data with broadband RGB, so it's better to do this separately, making it nice and clear as well I think. You can produce all mono data at once and create the integrations. Then the RGB and then you can use that data in Combine RGB to mix in the mono data.

@vincent-mod

Thanks for reply Vincent !!!

But how can I do it separately ? 
Have any workflow or some instructions ? I use this workflow but seems don’t work good ...

https://www.astropixelprocessor.com/community/tutorials-workflows/combining-r-g-b-with-ha-oiii-data-using-an-optolong-l-enhance-filter/

So where does it go wrong for you in that workflow?

@vincent-mod

In beginning of post have two pictures with before and after star color calibration... 

Do you want to upload my files to check them ?

Ah sorry, I didn't look close enough there. So, those frames are the result of RGB Combine right? Combining RGB with the H-Alpha.. did you select only stars or also the galaxy itself? I think only stars would work better.

@vincent-mod
Yeah my files are RGB and HA combine... everything work great before star color calibration after this all meshed up ... I boxed only stars for calibration not the galaxy ...

Mmm, so you can ofcourse skip the star calibration then as that already looks good. But if you want I can have a better look as well, you can upload that one file to our server if you want, login/password: appuser

@vincent-mod
Sure !!! I will upload the RGB HA files 

in server to check them...

I will send you here in post the details of 

folder ... thank you so much Vincent...

@vincent-mod

I uploaded Vincent ...

The folder name is Stratos Sinathis M51

Thank you ...

The mean differences between the channels R,G,B are from 2.53 to 3.02, too low. So RGB il almost white. The mean difference between Ha and the other channels is ~ 11.12, 4 times more. 

@sda

The rgb data is split channels from Broadband filter With osc camera zwo 294 and the filter is L pro. The Ha data is extract from L enhance narrowband filter ... this is the workflow that I following> https://www.astropixelprocessor.com/community/tutorials-workflows/combining-r-g-b-with-ha-oiii-data-using-an-optolong-l-enhance-filter/

Yes that could be one of the issues. You can always lower the amount of Ha you use for instance. Mixing it 50-50.

I'll have a look today.

@vincent-mod

ok Vincent... I will waiting your processing... 

Thanks again ...

So here's what I got. I selected stars on the left hand side and another big box underneath the galaxy. It seems that the filters do change the broadband data a bit, so I tweaked the slopes a little bit to have the line go through the population a bit better (that's the white line in the correction graphs). I also made a comparison with 50% Ha into the red and 33% Ha into the red. Before I combined all panels, I first did light pollution correction to have a nice background, all similar to each other.

This is right after combination with 50% Ha;

This is with color correction and a tweaked slope of the line. I also lowered both Magenta - Green slider to about -0.05 to remove a bit of green cast;

Next up, 33% Ha into red;

And with tweaked slopes;

Saturation was upped a bit to 0.19. Is this more to your liking? It does seem the colors could be more pronounced, what was the total integration time?

@vincent-mod

Hello Vincent ...

For sure is better than my processing ...

the total time is about 10 hours ... 7 rgb and 3 Ha

@vincent-mod

I think that before star color calibration you still get better result ...

What you think  ?

No, personally I don't think so. That first image looks very dull, color wise. So there seems to be an offset, created probably by the filters.

@vincent-mod

I can’t have good view from screenshots ... plz when you finish upload it in server to check it ...

Ofcourse, I uploaded the 33% Ha into Red final stretch in your directory on the server. The file is called "combine-RGB-image-33Ha-cbg-St.fits"