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Colour of interstellar dust

Acquisition Processing LRGB Dark Site
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John Walsh avatar
John Walsh avatar

I have been looking at many images of dust, such as is found around the Ghost nebula for example. It varies from brown to reddish brown to yellowish etc but I’ve also being seeing a lot of dusty images where the dust is almost white (not the grey of IFN). These seem to come from low Bortle areas with very high integration time.

So my (probably stupid) question is: Is this dust colour solely a function of post-processing or is there some other factor at play, like LP levels, mono with LRGB vs OSC etc?

Thanks for your patience if this is a foolish question

John

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andrea tasselli avatar
andrea tasselli avatar
Different dust and dust environments will give a different hue, plus difference in calibration and rendering. I'd like to think this is as neutral as possible:

Overview image of DR0.2 of Northern Sky Narrowband Survey in RGB without H-alpha.
Mikołaj Wadowski avatar
Mikołaj Wadowski avatar

My guess would be poor LRGB handling (overstretched Lum/understretched RGB) or not enough integration in RGB. Depends on the image, really. Sometimes it might be the difference in white balance choice, though I don’t think this is very common.

Tony Gondola avatar
Tony Gondola avatar

I guess the right answer is the mixed color of the starlight that illuminates it. I would think that because of that, it can vary but not a lot. In most good images I’ve seen it’s pretty neutral and as such it would be a very sensitive indicator of color issues. Almost like a grey card in conventional photography.

John Walsh avatar
John Walsh avatar

Thanks for the replies! It’s just interesting to me to see the variation in dust colour from the same object across images. Not sure if it matters from an artistic standpoint but I just thought it was curious

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Mikołaj Wadowski avatar
Mikołaj Wadowski avatar

Tony Gondola · Sep 26, 2025, 11:26 PM

I guess the right answer is the mixed color of the starlight that illuminates it. I would think that because of that, it can vary but not a lot. In most good images I’ve seen it’s pretty neutral and as such it would be a very sensitive indicator of color issues. Almost like a grey card in conventional photography.

Depends on the dust. What you said can be applied to IFN/high latitude dust, but as I understand it, OP is talking about the dust close to the galactic plane since they said

John Walsh · Sep 26, 2025, 08:56 PM

not the grey of IFN

The dust near the galactic plane is in general a fair bit redder than the IFN as shown by the NSNS RGB data, linked by Andrea. If you find an image with grayish/neutral dust in say, Cepheus, than it’s very likely a processing error. Far more likely than a deliberate choice, like different white reference imo.

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Brian Puhl avatar
Brian Puhl avatar

Trust the color calibration, this is your accurate color. It’s not uncommon to make subtle tweaks in the dust of a broadband image for taste however.

That being said, don’t always trust other folks imagery. Ha can be mixed with the dust. If an HaLRGB image is not processed utilizing continuum subtraction, then the resulting image can be very inaccurate.

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