Hi,
When you apply color calibration, offsets for the background in each of the color channels will be added/subtracted in order to equalize/neutralize them (align the sky histrogram...sigh, so many ways to say the same thing). But if you do not up-date your screen stretch you will certainly see an image as you present it. Did you press the auto-screen stretch transfer button again to give the expected view?
I note your selection for the initial white balance is a large area (Preview 2). In general you will want to select an object that represents your average white continuum - typically a face-on spiral galaxy- but otherwise anything that has signal and whose light includes all of the colors you define an average as "white". In fact it appears there is such an object in your image! (There looks to be a galaxy in there). Perhaps I am not seeing the rest of the galaxy because of the clipping.... but you would only want to select the part of the galaxy (likely more towards the center) with significant signal.
The way you have it now, it is likely to take into account the stars in the preview for the white balance... which is perfectly fine. However, you are also including the sky in the calculation which may bias the result. This is why there is the second section for "Structure Detection"... you could use this instead to just use the stars in the image and not include the sky contribution (by not including the smallest scales).
So... you might consider drawing a smaller preview around that galaxy... or using structure detection on the entire image. But regardless, update the screen stretch?
-adam
