Does luminance work as mask in LRGB combinations?

[chrisvdberge]

I was wondering what 'exactly' the role is of luminance in RGB and more specifically how the combination technically works. I understand the Luminance is for the details in the image, but does it work as an 'intensity guide' for the color or does/can it work as a mask as well?

Reason I'm asking:
I'll be using a duo setup soon (in Namibia) where I use a monochrome DSLR in combination with a color (modded) DSLR. The monochrome will be used on a better scope. This doesn't matter much I'd say, as the other scope is mainly used for the color and not the details anyway. However, I'm wondering how this will work with stars. Obviously the narrowband/luminance images will have tighter stars and I would want to use that as profile.
I thought I could create a luminance from Ha and OIII (or simply take the luminance image when shooting L) and use that as mask to combine the L with RGB using Pixelmath. (similar as how you'd use RGB stars in a NB image).
That made me wonder if LRGBCombination is actually doing this already? If not, would you say this could work?

[aworonow]

As I understand, luminance is an attempt to depict the eye's response to different intensities of light. It quantifies the number of photons (by a linear equation) of wR+uG_tB photons passing through a fixed area in 3D space (adjusted to the range 0-100). That's all it is.... Nothing to do with being 'for detail' or such.
Beyond that, not sure I follow where you're going with the NB and LRGBComb. questions.

Alex

[chrisvdberge]

That's more or less what I meant Of course the perception of detail comes from this depiction of intensities of light. With 'for detail' I meant that typically you process the Luminance with the goal of enhancing this detail, while you don't for RGB. (I even notice some workflows mentioning blurring the RGB data a bit)

To rephrase my question a bit different;
Let's just look at one star in detail; the Luminance/narrowband will have a tighter star. Usually just less bright in NB, but in my case due to the different scope probably tighter. What happens to the data of the region around this NB star that is now background in the Luminance layer, but 'still' star (halo) in the RGB image when you combine the two with LRGBCombination?