1. Set appropriate capture parameters so that the stars are not too burned out and keep enough of their color. I usually use an ISO 800 (or even lower) and close the aperture 1 or 1.5 stops (so that the aberrations of the optics are reduced to a minimum and the stars are perfectly sharp).

2. Shoot in RAW and then import the RAW directly into Nebulb. I never work with JPEG because, among other things, they do not allow to recover any color from the brightest part of the stars.

3. Do not activate color noise reduction.

In case the stacking you do in Nebulb is specifically to obtain a star trails image (like a circumpolar one) it is not recommended that you activate the color noise reduction of the "Preprocess" module, because this option greatly reduces the color of the star trails.

ADVICE: In case the images have many hot-pixels and you are going to make a star trails stacking, it is advisable to apply only the luminance noise reduction. Also, there is no problem in activating (if you consider it convenient) the reduction of chromatic aberration and vignetting.

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