Deer Lick odd colour balance

[DaveS]

This is doing my head in. OK, there's only 6 hours RGB and 2 1/2 hours Luminance binned 1x1 as yet but the colour balance is doing my head in.

 

Looking at NGC 7331, I would expect to see a yellowish core and sparkling blue arms, but the coer is blueish and the arms a nondescript mud

Images through my 13 f/7 triplet and Trius 694 with Baader filters.

Stacked with sigma Average and Bias only in AstroArt 5, Trichromy with Auto levels and White Balance then LRGB synthesis. The resultant image just had DDP, then saved as FITS and JPEG.

I wondered if I'd got the filters in the wrong order (Done that before with NB) but they're OK.

Any ideas? I do have Maxim DL6 on the office computer, but it looks a steep learning curve compared to AstroArt.

[Davey-T]

Saturation on galaxy only in PS.

Dave

 

[DaveS]

Thanks Dave, that looks much better. I don't have PS, maybe I can do something similar if I install the latest GIMP. Layer mask around 7331?

I tried a saturation boost in AA but before I got anything like that I was seeing severe artifacts, and that was working on the FITS.

[vlaiv]

You are not far off ...

Colors are a bit washed out due to the way you processed the image, but in principle it is fairly close to what it should look like.

Don't be swayed by majority of renditions of this galaxy found online - most are just too saturated and generally not quite correct.

Color renditions like these:

are overly saturated and blue is pushed far more then it should be.

On the other hand, renditions like these are closer to the real thing:

Look at Hubble rendition of central part of this galaxy:

Blue is rather scarce in outer arms, and mixed with Ha regions so its more "purplish" than pure blue, core is deep yellow / orange surrounded by ring of gas and Ha regions - which have deep red / brown look.

Here is one of mine images where I was playing with getting correct color for this target:

[DaveS]

Thanks. I've downloaded GIMP 2.10.12 which I'll try to get a play with tomorrow. Meanwhile here is an overall saturation boost. as you can see there are green artifacts in 7331

[vlaiv]

1 minute ago, DaveS said:

Meanwhile here is an overall saturation boost. as you can see there are green artifacts in 7331

Yes, quite close to what it should be and you are right about green cast in center - lowering green component will create center of the galaxy more yellow like (red+green = yellow).

[DaveS]

I've had a fiddle with the Green level and contrast, and think this is as good as I'm going to get it as it stands.

It desperately needs more Luminance, as there's only 2.5 hours as it stands. I may have a go in Maxim, but think it's a pretty steep learning curve, and not as beginner friendly as AstroArt.

[Gina]

GIMP has come on well in the last decade or two.  I use it quite a lot to stretch images and adjust saturation and other colour settings.  For the full job of astro image processing I use PixInsight.  To me it was money well spent.  Steep learning curve mind you but then so was Photoshop!

Edited September 8, 2019 by Gina

[DaveS]

Yeah, I guess I'm going to have to bite the bullet and look at Pixinsight.