We are getting to the final part of astrophoto editing with PixInsight. Integrating a Luminance with our color image helps add brightness and clarity to our image. We want to make additional, and final changes to the brightness of our high and low signal areas.

Note: The remainder of the adjustments are minimal.

Foreground Brightening

As part of the final brightness adjustments, we might want to brighten the portions of the image. Usually, I’ll have one area that his already quite bright with a significant more with medium intensity. If I want to brighten the bright areas, I can use the same range mask created with the Final Color Saturation explanation. But in this case, I want to brighten some of the medium intensity features. For this I’ll create a new range mask.

Range Selection
Range Selection – Mask

Lowering the upper limit allows the mask to remove the brightest areas. Once this is applied, I can then use Curves Transformation to brighten the mid-range content.

Curves Transformation
Curves Transformation - Brightening Details
Curves Transformation – Brightening Details

I first add a slight S-curve to the RGB/K channel as this will improve the contrast slightly.

Secondly, I slightly increase the Lightness (L channel).

These are minor adjustments, but help bring out the details.

Background Darkning

With the detail brightened, we might wish to darken the background. Just a word of caution, the background of astrophotos should NOT be completely black. Doing so will make them appear fake and over-processed. We just want darken the background slightly to add more emphasis to the high signal areas.

Curves Transformation
Curves Transformation
Curves Transformation - Darkening Background
Curves Transformation – Darkening Background

As you can see, the adjustment to the Lightness (L) channel is minor as my background was quite dark to begin with.

What’s Next

Let’s take a quick comparison between our before and after brightness adjustments.

The final step before publishing is to do any last noise reduction with ACDNR, but just like the final color and brightness adjustments, the noise reduction will be minimal.