Hi there, in light of the K-man's recent posting of Uranus and Neptune, I thought I'd ask this question that has been bugging me a bit since I started in this caper. It concerns the colour correction I've been applying on Jupiter and Saturn to get them to look "good", or at least to give me the colours I'm expecting to see (and that everyone else gets). This then leads onto the "correct" colour cast to apply to Uranus and Neptune, assuming there is one.
Firstly, I'm using the white balance values that ASI recommends for the ASI224MC, which are WRed=52 and WBlue=95 (well, I think I am, I didn't change them from the default values and the log file says they are "off").
When I take take images of Jupiter, the stacked and sharpened images are quite green looking, and I have been using Registax 6's "RGB autobalance" to give me the colours it thinks are correct, this results in a nice looking image with values Red 1.09, Green 0.94, Blue 1.09 (see image below).
For Saturn, the suggested colour shifts are Red 1.03, Green 0.96 and Blue 1.18 (second image below).
Then the question comes of what colour correction should be used for Uranus and Neptune. Obviously they are blue in colour, so using the RGB autocorrect in R6 doesn't work, you get a "white" looking planet as it bumps the red up to huge values. The histograms I get for these planets are shown below (Uranus 3rd, Neptune 4th), and since the histogram is nice and blue (or blue/green), and I'm expecting to see blue or blue/green, I don't play with the colour settings at all.
However, given that Darryl (and others) are seeing a rosy glow on Uranus using a mono camera and filters, should I be colour correcting my images to make them more "accurate"? I do it for the larger planets, why not Uranus and Neptune? Should I use figures similar to those I use for Jupiter and Saturn? Something else? Is there a theoretical shift that should always be applied due the scattering of light from Earth's atmosphere that is proportional to the altitude of the target? Or should I simply not bother about it too much as this is a direct result of using a colour camera in the first place? Or just be like the mice from Hitchhiker's Guide to the Galaxy, and just make something that looks good?
Interested in your thoughts.