Variations in colour

[morls (Stephen)]

I've been looking at all the great images being posted, especially of Mars, and it's very interesting to see the variations in colour. I'm wondering what the cause of such variation may be?

In my images, I take the stacked LRGB across to GIMP and build up the colour image there, without any processing aside from assigning each to the appropriate channel after colourisation. I also keep the gain the same across all filters when capturing a sequence, my thinking being that this will give a natural balance.

So, my general question is, how is it that there is such a variation in colour between all these images?

[multiweb (Marc)]

Originally Posted by morls

I've been looking at all the great images being posted, especially of Mars, and it's very interesting to see the variations in colour. I'm wondering what the cause of such variation may be?

In my images, I take the stacked LRGB across to GIMP and build up the colour image there, without any processing aside from assigning each to the appropriate channel after colourisation. I also keep the gain the same across all filters when capturing a sequence, my thinking being that this will give a natural balance.

So, my general question is, how is it that there is such a variation in colour between all these images?

Don't look or wonder about the color in my shots.

[morls (Stephen)]

[PKay (Peter)]

A much asked question Stephen.

I have asked it, as we probably all have.

In the end, colour choice is a subjective thing. Use it to bring out technical detail, or create a pleasing and pretty picture.
It is the choice of whoever is doing the processing.

Natural colour?
It may be the OSC goes close to capturing natural colour, but who knows.

If you want to get technical, there are standard star colour charts available. Worth having a look at.

Also, to get the best colour (dynamics), avoid saturating the pixels!

[glend (Glen)]

Stephen, Astrophoto processing has no rules, colour can be anything you choose. Arguments about narrowband image colourisation have gone on for years. Yes absolutely a few people might jump on your images and say you should do it this way, or use this tool, etc. All that really matters is that you are pleased with your results.

[Tulloch (Andrew)]

I actually believe the the colour of the planets can be completely defined, it's our perception of the planets that is subjective.

Without launching into a complete diatribe, the colours of the planets can be completely determined using something like an imaging spectrophotometer, where the wavelength spectrum at each pixel can be measured and used to convert to the "colour" of that pixel using the CIE 1931 standard on tristimulous colour coordinates. Now, these things are quite expensive and out of the range of the amateur AP, but it is possible.

Others have measured the average colour of the planets using a spectrophotometer (you can see my investigations into this here and here if you have a few hours to kill ), but in the end you have to produce an image that you are comfortable with.

The most accurate colour image of Mars is probably shown here, taken from the Rosetta spacecraft, together with Damian Peach's thoughts on how we all butcher the colour of Mars
http://www.damianpeach.com/marscolour.htm

Andrew