exceptional posts guys - heartfelt thanks.
I initially thought I was working towards a systematic method for representing galaxies etc "realistically". Looks like there is no such thing..
I still have difficulty accepting that the image presentation need not have much reference to an underlying reality - but it looks like everything in an image actually starts out corrupted anyway - having stars of varying sizes is an artefact, available detail is normally determined by the atmosphere (which has nothing to do with the object) and the true colours (whatever that might mean) will never be visible to a human.
I think I am coming to the position that Pixinsight provides a good starting point for acceptable colour (good link thanks Geoff) and that I will just have to tweak beyond that to show what I consider to be interesting in whatever colours I think are appropriate. Darn, I hoped to get to something more concrete than that . Suppose an ex physicist should have known that things get less comprehensible the deeper you look...
so the rules currently are:
- Pixinsight automated processes for basic galaxy colour balance + individual tweaking to personal taste
- no green stars or background colour casts - and saturated stars are white
- emission nebulae can/should have "neon" saturated colour
- enhanced colour saturation and sharpening applied elsewhere with care to enhance features of interest
- no artificial "super" enhancing to create features where none exists
- need to spend some time getting to understand Excalibrator
Again, all of the posts to date really have been extremely helpful and full of information - thanks
regards Ray