Help with colour balance please!

[astroman001]

Calling on any experienced deep sky imagers out there..............I have a C11 and a one shot colour SBIG ST2000XCM CCD camera. I manage to get good colour balance in gaseous nebulae, planetaries, comets etc but not galaxies.

For example I have attached an image of M81 from earlier this year. The 'best' images of M81 I have seen show yellowish cores and bluish arms with a smattering of red star forming nebulae in the arms.

I know I don't have the ability of adding Ha data, but I can't get a decent colour contrast between the arms and the core. It all looks a bit bland.

I am starting to doubt the CCD or perhaps it's my processing, but I've tried many different ways to get the colours 'right'.

Any ideas what is going wrong??????


Best regards

Peter

[disraeli]

Pete, please excuse me being very much a begginer on this but I did a bit of work in CS4.  Increased saturation and stretch in curves.  It's a good picture with lots of data.  Keep playing.  Here is my take on it.   Fred.

[astroman001]

That colour balance is so much better! I have CS2 and have tried everything. Please tell me what steps you used. Need to watch burn out in the core though.

Many thanks

Best regards

Peter

[Einari]

The colour might be better but now there are dark halos around bright stars.

[astroman001]

Thanks for pushing me in the right direction. I've just not pushed the colour enough. Attached is a new version with increased saturation, colour balance, levels and contrast adjusted.

regards

Peter

[roundycat]

your first picture was better than the other two. Once you have stretched the image enough that you can 'see' it try gentle increases of saturation, no more than +20, maybe twice. The best clue in your original is that there is no star colour. You may have moved the white point, deliberately or accidentally, during your stretching and that has saturated one or more channels. From that point on there is no hope, you have to go back and start again being careful never to move the white point.

You may be able to rescue some colour difference by using Image-Adjustments-Selective Colour but be careful not to make the moves too big.

Dennis

[astroman001]

Dennis,

How do you avoid saturating a channel? What do you look for?

I used DDP in Maxim as the first step before finishing in Photoshop.

Cheers

Peter

[roundycat]

Any curves move that causes the top right of the curve to become a straight line along the top rh side of the graph is a no-no. As Levels and Curves duplicate the basic function it is possible for a radical Levels move to do the same thing only the dialogue does not show you. This might help

http://www.dens-astropics.org.uk/page%2023.htm
http://www.dens-astropics.org.uk/page%2022.htm

The Info palette gives you most of the information you need. As you stretch keep mousing over the brightest part of the picture and look at the channel values in levels (0-255). Do not move the white point voluntarily.

Dennis

[astroman001]

Thank you.