PixInsight’s ScreenTransferFunction (STF) and HistogramTransformation tools offer a "chain link" icon. When clicked, this forces all three RGB channels to use the same shadows/midtones/highlights parameters. In a linear image, this is a powerful act of discipline.
If you link the channels in the linear stage, you preserve the relative ratio of the signal between red, green, and blue. For example, if the red channel in the Horsehead Nebula is slightly brighter than the blue channel in the raw data, linking ensures that when you stretch the histogram, the red stays proportionally brighter. This yields a raw, unstretched color balance that reflects the actual physics of the object, filtered only by your camera’s quantum efficiency. pixinsight lerar link
⭐⭐⭐⭐⭐ (5/5 for advanced users)
⭐⭐⭐ (3/5 for beginners)
If you’re serious about astrophotography, it’s worth the investment. For casual editing, use Siril (free) or AstroPixelProcessor. Now for the main event
Now for the main event. We are going to combine the Luminance (L) image with the RGB image you just created. Lightness Settings:
Lightness Settings:
Apply the process to your target image.
The Result: You should now see a significant increase in detail and contrast compared to your original RGB image.