[IanP]

Originally Posted by gregbradley

That's a very good lens image. Nice and widefield and shows up a lot of structure.
Flats divide the value of the pixels into the main image. So you can't divide by zero and I assume that's what that error message means.
How did you make your flat? Is it about 12 frames median combined and about 20- 30,000 ADU each?
Greg.

Thanks Greg,

I took 30 flats, as I usually do, calibrated them with bias & darks, as I usually do, and integrated them in the same way as I have been doing since I started using PixInsight. The only difference was that this time I adjusted the LEDs voltage in my light-box little bit lower, so the illumination inside the box was lower than usual.
The way I solved the problem was (trial and error) by slightly stretching the MasterFlatFrame and after that the calibration of all other colours and NB went smoothly through ..