Er . . . Howzat?

[Astrosurf]

Awww, you guys!

I'm trying the same as you but cannot get the detail you have. This is as far as I have managed to push it with the techniques you've used.

Dead dull.

[roundycat]

You should never use a coarse filter like High Pass on stars.

Astrosurf, the reference you make to 'layered distortion' is, I believe, a comment on the colour banding seen in Earl UK's re-work. Because the thin data has been stretched to a hideous degree there is hardly any data left to 'fill up' the 256 quantisation levels present in a good picture. This is a classic case of Posterisation. So called because you get just a few colours, like in an advertising poster, instead of 256 shades in each channel giving you 16 million odd colours. You'll never achieve that in an astro picture but the 'Comb' like effect you see in the histogram is something to treat like the Devil himself. Stay away from it!

Dennis

[Astrosurf]

Thanks Dennis. I can't seem to avoid the peaks in the histogram separating! How do I avoid this? I'm only using curves and a tiny bit of High Pass. You all seem to have an instinct for this that I lack!

[roundycat]

A couple of things to remember!

1/ The three (or two) peaks in the histogram merely mean that you have an imbalance in the background colour. The bulk of the peaks show the sky background and you can see from the Info Palette reading that they are miles out of balance.

Equal values for Red, Green and Blue will give you a grey sky which may not be right but I have gone for neutral to keep it simple.

2/ The second picture, v2, (may not be the second because I can never get them to post in the right order) shows an even spread of values in the Info Palette. The only way you will ever get the background neutral (for instance) is to measure the values.

3/ The comb like appearance in the last pic (v3) should not be confused with the three peaks in v1. This is a hopelessly overstretched picture and the comb indicates severe posterisation.

Hope this all makes sense.

I adjusted the background colour bias using Curves. First off, measure somewhere in the pic, as shown by my white arrow. Pic v1 shows widely different values, pic v2 shows them all the same. The values were set to a loose average of the original channel values, about 18-19. Doing it this way rather than raising them all to the highest value or lowering them to the lowest value keeps the Luminance about the same. If you have to move the bottom of the curve a fair way (and you will) make sure you anchor the curve further up to keep it in a straight line.

Dennis

[Astrosurf]

Thank so much Dennis. I'll need time to work through this! I'll let you know how I get on. Back to work now after some leave, apart from this long weekend, and so I might be some time!

I really appreciate everyone's help.

XXX