There is some easy way to do that. Check the Trilogy by Dan Coe. The introduction on the website is quite enough for first using.
Another way I found is the
Here is a paper about one method to create the rgb images (http://arxiv.org/pdf/astro-ph/0312483v1.pdf). Some examples are here (http://www.astro.princeton.edu/~rhl/PrettyPictures/).
The thing you should think about is that these images have large dynamic ranges as shown below.
| Human Eye | 10,000:1 |
| CRT | 100:1 |
| Real-life Scenes | up to 500,000:1 |
In real life, the images always contain a large range of flux. It is quite bright in some points, but it is dark in others. So if you use a linear plot, some details will not be obvious. So you should think about to rescale the image. Unlike you take photo in which you should make longer exposure inside room, the exposure time you use is better for longer. For longer exposure time, you can detected faint sources. In the plot, if you want to show these faint sources, some bright objects will be too brighter and make the figure too ugly. Right? The thing is about how to make a good contrast with keeping enough informations. now let us compare different scale methods.
Check the above, for the same observations, it seems different. If you are familiar with DS9, you can try these scale with any fits file. I use log scale usually. There is a comparation of the stretch function.
In order to show some more details about faint objects, I suggest to use log scale or even log(log) scale. In Trilogy sofeware, Coe uses the scale method:
y = log10( k * (x - xo) + 1 ) / r
# Current settings:
# x0: 0 (0 in the input yields black in the output)
# x1: mean + std (1-sigma above the noise)
# x2: set so only some small fraction of pixels saturate (with output = 1)
The x1 and x2 is determined by the two parameters satpercent and noiselum.
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