How to I get the "correct" colour on my deep sky pictures?

[Quetzalcoatl72]

Not sure what topic to put this in but I've been struggling with deep sky stacker, because of my optlong ccd light pollution filter most nebulas come out one shade of red, for example the Monkey's head nebula, see attached example. Dumbell and ring turned out as seen online and Stellarium. All 3 images were taken with a rct f/8 and a canon 600DA. I've never tried these objects without the filter as I got new equipment and this is the most active I've been in my hobby for many years. I'm not spending hundreds or thousands on software so preferably if i can get the correct colour on these with dss or some other free/semi free software that would be great. Thanks 

 

[happy-kat]

Hi, looks nice data to work with there.

GIMP is free and offers a processing approach similar to say photoshop but without the 3rd party add on action scripts though there are plugins I think. Affinity photo sometimes on offer for around £29 and similar to GIMP. If astro focused then there's StarTools for roughly under £40 to process the output of DSS and I'm biased as it's inexpensive but very capable and compliments the data I have (not that good my data) and it offers excellent modules for manipulating data. I expect you could adjust the colour in your images using GIMP as it's pretty capable and offers so much more than free basic tools in DSS for working on the stacking output.

 

[michael.h.f.wilkinson]

The red colour is actually correct, as H-alpha dominates these nebulae. I use APP rather than DSS. APP is not free, but I much prefer it. It has a "calibrate star colours" tool which works well on most RGB data, I find. After that, I tend to increase saturation in GIMP a bit

[happy-kat]

I wonder does SIRIL have something to do on star colours as well and it's a free stacking program but with added functions that can be run before then processing the output in say GIMP 

[KevinPSJ]

I've found startools works really well - it's not free but would definitely fall in the "great value for money" bracket. I'm getting much better colours out of my data now ... using siril for calibration, registration and stacking and startools for stretching and colour balancing.

[alacant]

Hi

Nice shots:)

Using a cls filter will remove much of the visible spectrum so as you can see, it is impossible to obtain natural colour, especially in stars.

Your best bet is to take a few frames without the filter and layer that over your cls stacked result. The non-filtered frames need not be long. 15s-20s is normally fine. The best app I've found for that and just about every other aspect of processing astro-images is StarTools as @happy-kat has already recommended. So a +1 from me. 

The best app I've found for stacking and calibration is Siril which also has an excellent photometric colour module. This will may help you along the way with the colour if you are using solely cls frames.

Cheers

 

Edited April 16, 2021 by alacant

[alacant]

12 minutes ago, happy-kat said:

does SIRIL have something to do on star colours

Yes:

[Fivel]

In answer to your question, I use Siril for almost registering and stacking, and some post processing. Then I finish up with Affinity Photo (AF).

Siril has some great post stacking tools for getting the colors correct, such as Photometric Color Calibration.

That tool uses plate solving to get the star colors correct.

AF is half price with the latest versions. It is equivalent to Photoshop and has some astrophotography specific tools, such as astro stacking and Background removal tools. It also has many color pallets and can work in 32 bit operations.

May you get the colors you desire.

Fivel

 

 

[Quetzalcoatl72]

Thanks guy's I'll look into them while the clouds are in for the week