Colour balance

[+Stu]

Hi folks. So I'm getting to grips with processing a bit now in Affinity, but I struggle when it comes to colour balance. @Bob Dobber Your M42 images are really nice, I've been comparing your 1100D image to mine as it's DSLR and I can't seem to get the balance right with my data. 

After doing a bit of reading up I think I might be trying to bring out colours that aren't there in the first place. Are there only certain colours I need to be adjusting? ie red and cyan for any kind of emission nebula? 

Also with a modded DSLR, should I only be using broadband/narrowband filters on emission nebula? Or a combination of filter/no filter for best results?

[Bob Dobber]

Thanks for kind words, but I'm afraid I'm using a cooled mono astro camera (183-MM Pro) and generally leave colour calibration/balance (I think they're the same thing??) to Pixinsight via PCC or similar. A very very good astrophotographer friend uses Affinity (I have it too and have yet to invest much time into it) and he is constantly bemoaning the pain of colour balancing to the point that he's going back on his oft-stated refusal to "give in" and to use PI... So it may be that it's not that easy in the first place! I think there's a few videos on YouTube about Affinity and astro, have you taken a look? Good luck with it!

[Clive]

As you say, if your LPS filter is removing parts of the spectrum then you can't get them back. You could try imaging M42 without the filter to see what difference their is (if any).

[+Stu]

Thank you both. I'll try doing subs with and without and see what I get. I might also see if I can get different results doing the colour balance in the GIMP. Pixinsight is a bit out of my reach at the moment. 

[+Stu]

On 19/12/2022 at 08:53, Bob Dobber said:

I think there's a few videos on YouTube about Affinity and astro, have you taken a look?

There's plenty on there, I'm still getting to grips with it but getting on ok so far. 

[+Stu]

On 19/12/2022 at 10:43, Clive said:

You could try imaging M42 without the filter to see what difference their is (if any)

I was wondering if there are any camera settings I've got on/off that could be affecting it. 

[Clive]

57 minutes ago, Stu said:

I was wondering if there are any camera settings I've got on/off that could be affecting it

I assume you're stacking using DSS. If that's the case then apply the following settings:

    RGB background calibration.

    Reset all white balance settings.

And if your using bias frames:

    Set the black point to zero.

(These can found in the Recommended Settings prior to stacking)

I find with these settings I don't really need to do any colour balancing in post processing.  However my camera is unmodified so if your camera is modified you may need to back off the red channel in post processing.

If you do set DSS to use the camera RGB balance (DSS extracts it from the image metadata) then make sure the camera RGB setting is always set to Daylight rather than the default Auto as that can lead to the incorrect processing of the calibration images (flats, darks, bias) compared to the lights.

[+Stu]

10 minutes ago, Clive said:

I assume you're stacking using DSS

I am indeed. There was no background calibration set so I e changed that. I assume the "monochrome 16 bit FITS files....DSLR" option doesn't need to be ticked as I'm shooting in colour?

[Clive]

 

23 minutes ago, Stu said:

I am indeed. There was no background calibration set so I e changed that. I assume the "monochrome 16 bit FITS files....DSLR" option doesn't need to be ticked as I'm shooting in colour?

I assume you're stacking Canon CR2 RAW files, in that case you can ignore  any settings in the FITS file tab (just leave as the default settings) and set the settings in the RAW file tab:

   No white balancing: Unchecked

   Use camera white balance: Unchecked

The other important setting is to enable RGB Background calibration as it sets the median value of each RGB to the same value (so the background appears black)

Edited December 20, 2022 by Clive
Typo

[+Stu]

Yes, CR2 files. I'll give them another stack later with the background calibration on. Thanks 👍

[+Stu]

I restacked the LPS filtered data on it's own and it's better with background calibration. The colour is there, it's not being helped by the image centre being so bright though. I'll have another go when I get some time.