How does APP treat luminance data?

Hello folks,

I finally got a reflector telescope with no chromatic aberration problems, so now I can use my luminance filter.  I was promised by the mono camera + filter wheel people that I can use L as "detail" and RGB to "fill in color".

Anyway, so I use APP with the default settings (plus enable align channels) all the way to 6)integrate and I end up with a set of integrated frames.  So far this seems to work fine.  But then when I use the RGB combine tool and try to add in L, all it seems to do is "add white", and thus it washes out all the star colors.  I then have to use the saturation setting to try to bring the colors back, but it's still not as "natural looking" as plain RGB.

I "think" what you are supposed to do is to have the L channel set the intensity of a given pixel, and then look at the ratio of r/g/b to figure out what is the color.  If the rgb data is too faint, just give up and call it white (or grey-ish).

So anyway, what happens is that if I use plain RGB, then very faint stars are lost, and the background  (after some subtraction) looks to be a faint speckling of red and green noise, which is "obviously wrong" (chroma noise?) and probably could easily be removed by some noise-reduction algorithm.

The other thing I have been doing is only adding in 50% L, and then go to the saturation slider and crank that up until the star colors start to come back.  The good thing is that some faint stars start to come back.  The background noise is now more grey. (Luminance noise?)