Hi Marzio,
I just found the problem: the Vizier database gives errors in this sky area. If you decrease the limiting magnitude to 7, you get 2000 stars in a field of 2-3 degrees! This is the workaround:
- Create a preview around NGC6888. Mine was around 1000 pixels wide.
- Create a new, independent image from the preview and apply PCC to it. Don't apply PCC to the preview but to the new image.
- Take note of the RGB weights in the console.
- Apply a PixelMath process by multiplying each color channel of the full image by its corresponding weight. The weights I get are 0.824 for R, 0.868 for G and 1 for B.
- Apply BackgroundNeutralization manually.
In an upcoming version of PCC you'll be able to define a region of interest in the image, so it will be possible to apply this workflow directly in PCC.
Best regards,
Vicent.
